In addition, involvement of the sinus node and the atrioventricular conduction system is very frequent in patients with CCCD. Sinus node dysfunction can manifest as bradycardia or even sinus arrest, second-degree sinoatrial block, junctional rhythm, and accelerated idioventricular rhythm. First-degree atrioventricular block (AVB) is one of the most frequent atrioventricular conduction disorders, and can be transient or permanent. Second-degree AVB is less frequent and classified into the following types: Mobitz I (Wenckebach), Mobitz II or advanced-degree. Third-degree or total AVB (TAVB) can occur in 10% of the patients, being more frequent than in any other acquired cardiopathy. Atrial fibrillation tends to manifest later, usually associated with more advanced degrees of systolic dysfunction and ventricular dilation.

The arrhythmias can be asymptomatic or cause palpitation, dizziness, dyspnea, weakness, presyncope, syncope, or cardiac arrest. Sudden death accounts for 50% to 65% of the deaths due to CD.³⁵² Sudden death is usually precipitated by physical exercises and can be associated with SVT or ventricular fibrillation (VF) and, less frequently, asystole or TAVB. Approximately 40% to 50% of the cases of sudden death are asymptomatic prior to the fatal episode, but most patients have concomitant severe impairment of the ventricular systolic function and of the conduction system. The severity of ventricular arrhythmias tends to correlate with the ventricular dysfunction degree. However, differently from other diseases, patients with CCCD and malignant ventricular arrhythmias may present relatively preserved LV global function, but with regional dyskinesias indicating localized fibrosis.³⁵³ Episodes of malignant ventricular arrhythmias are much more frequent in patients with CCCD than in those with other forms of cardiopathy, such as the one resulting from coronary artery disease or DCM of other etiologies.³⁵⁴⁻³⁵⁶

### 5.2.4.3. Heart Failure Syndrome

Heart failure manifests in many patients throughout the natural history of CCCD, usually with biventricular dysfunction, including early symptoms, such as dyspnea, fatigue, lower limb edema, and atypical chest pain. Diastolic dysfunction can be observed in the early stages of CCCD, in the absence of regional or global LV systolic dysfunction, and can be explained by a certain degree of LV diffuse fibrosis.³⁵⁷

As already mentioned, in some patients, right HF can be more prominent than left HF, but RV dysfunction, when clinically manifest, is usually associated with LV dysfunction in an advanced stage of CCCD.³⁴³,³⁴⁹

The classification of HF of CD etiology, considering the presence or absence of functional and/or structural defects in general and LV systolic function especially, is useful when applied to CCCD, after mild modifications from the 2011 SBC guidelines, enabling the identification of different subgroups or evolutionary stages from the prognostic and therapeutic viewpoint.¹ The HF classification according to LVEF is shown in Table 5.1. The classification into progressive stages is shown in Table 5.2.

<table><caption>**Table 5.1 – Chronic cardiomyopathy of Chagas disease: normal systolic function and heart failure classification according to left ventricular ejection fraction (LVEF).**</caption><thead><tr><td>CATEGORY</td><td>CRITERION</td></tr></thead><tbody><tr><td>Normal global systolic ventricular function</td><td><ul><li>LVEF ≥ 55%</li><li>- without segmental dysfunction</li><li>- with segmental dysfunction</li></ul></td></tr><tr><td>Heart failure with mildly reduced ejection fraction (HFmEF)</td><td><ul><li>LVEF between 41% and 54%</li></ul></td></tr><tr><td>Heart failure with reduced ejection fraction (HFrEF)</td><td><ul><li>LVEF ≤ 40%</li></ul></td></tr><tr><td>Heart failure with improved ejection fraction (HFimpEF)</td><td><ul><li>Baseline LVEF ≤ 40%, a ≥ 10-point increase from baseline LVEF, and a second measurement of LVEF > 40%</li></ul></td></tr></tbody></table>

### 5.2.4.4. Systemic and Pulmonary Thromboembolic Syndrome

This syndrome is very common in CCCD, venous and arterial thromboembolic phenomena being the third cause of death.³⁵²,³⁵⁸ From the clinical viewpoint, thromboembolic phenomena to the brain predominate, followed by embolism to other systemic organs and limbs, and lastly by pulmonary embolism diagnosed during life. Stroke can be the first devastating manifestation of the disease.

The high frequency of the thromboembolic syndrome in CCCD can be due to several factors that can predominate depending on the disease's phase. Thus, the apical aneurysm can be an early alteration in CCCD, but, more commonly, thrombosis in systemic veins that can cause pulmonary embolism are complications of HF, when cardiac output and venous return are hindered. In the presence of HF, dilation of the chambers favors atrial and ventricular mural thrombosis, causing systemic and/or pulmonary embolism. Atrial fibrillation is more frequent in advanced cases of CCCD, increasing the risk for thromboembolic complications.

Chagas disease is a major cause of stroke in Latin America, accounting for up to 20% of this complication in endemic areas.³⁵⁸⁻³⁶⁰ The incidence of stroke in patients with known CD ranges from 0.56 to 2.67 per 100 individuals-year.³⁶¹ Thus, CCCD should be regularly included in the differential diagnosis of stroke in Latin America.³⁶² Ventricular systolic dysfunction, enlarged left atrial volume, apical aneurysm, cavitary mural thrombosis, and arrhythmias, such as AF, seem to be important risk factors for stroke of CD etiology, characteristically of cardioembolic nature.³⁶³ In 50-70% of the patients, stroke manifests as a partial anterior circulation syndrome, which includes two of the three signs: motor or sensory deficit involving face, arm and leg; homonymous hemianopsia; and upper cerebral dysfunction, expressed as aphasia or visuospatial deficit. Less often, patients will have lacunar or posterior circulation syndrome.

A risk score for stroke (IPEC-FIOCRUZ) has been developed in a prospective observational study with 1043 patients.³⁶⁴ As discussed in a specific chapter of this guideline on thromboembolic complications of CD, that score needs to be reviewed to contemplate updated scientific considerations.
<table><caption>Table 5.2 – Classification of chronic Chagas disease into progressive stages.</caption><thead><tr><th rowspan="2">Characteristics</th><th colspan="2">Indeterminate form</th><th colspan="4">Chronic cardiomyopathy of Chagas disease</th></tr><tr><th>Stage A</th><th>Stage B1</th><th>Stage B2</th><th>Stage C</th><th>Stage D</th></tr></thead><tbody><tr><td>ECG</td><td>Normal</td><td>Altered</td><td>Altered</td><td>Altered</td><td>Altered</td></tr><tr><td>Segmental ventricular dysfunction</td><td>Usually absent</td><td>May be present</td><td>May be present</td><td>May be present</td><td>May be present</td></tr><tr><td>LVEF (ECHO - Simpson)</td><td>≥ 55%</td><td>≥ 55%</td><td>&lt; 55% (usually between 41% and 54%)</td><td>&lt; 55% (usually ≤ 40%)</td><td>Usually ≤ 25%</td></tr><tr><td>Functional class (NYHA)</td><td>Not applicable</td><td>I</td><td>I</td><td>I, II, III or IV</td><td>IV</td></tr><tr><td>Cardiomegaly (chest X-ray)</td><td>Absent</td><td>Absent</td><td>May be present</td><td>Usually present</td><td>Present</td></tr><tr><td>Complex ventricular arrhythmia (24-h Holter)*</td><td>Usually absent</td><td>May be present</td><td>Usually present</td><td>Present</td><td>Present</td></tr><tr><td>Myocardial fibrosis (late enhancement on CMRI)</td><td>May be present</td><td>Usually present</td><td>Usually present</td><td>Present</td><td>Present</td></tr></tbody></table>

# 6. Diagnosis of Cardiomyopathy of Chagas Disease

## 6.1. Methods to Determine the *T. cruzi* Infection

### 6.1.1. Introduction

The diagnosis of an infectious disease should be based on clinical, epidemiological, and laboratory data, which should be considered to confirm or rule out the diagnosis.³⁶⁵

Some clinical data can be very suggestive of CCCD, such as RBBB on ECG.³⁶⁶ However, there is neither a CCCD-specific electrocardiographic abnormality nor one occurring in all patients with the disease. Epidemiological data, particularly patient's origin from known endemic areas, aid in making the diagnosis. In addition, the family history should be taken, because two thirds of the patients from endemic areas have family members infected, particularly mother or siblings, or even report sudden death in their families.³⁶⁷

Laboratory tests can detect the parasite or, more commonly, the anti-*T. cruzi* antibodies. In the chronic phase of CD, most patients have low parasitemia and parasites cannot be found on the blood smear. Thus, the CD etiology cannot be ruled out based on the absence of the parasite. On the contrary, almost all chronically infected individuals have anti-*T. cruzi* antibodies at varied levels. Therefore, a clinician willing to confirm or rule out the *T. cruzi* etiology in a patient with heart disease should initially request serological tests.

### 6.1.2. Serological Tests Available and Which to Request

The serological tests available can be classified as conventional and non-conventional. Each laboratory uses different conventional tests, such as indirect immunofluorescence (IIF), indirect hemagglutination (IHA), enzyme-linked immunosorbent assay (ELISA), and, in recent years, non-conventional tests, such as chemiluminescent microparticle immunoassay (CMIA) and electrochemiluminescence immunoassay (ECLIA) in automated platform, in addition to rapid tests. Non-purified and purified products (recombinant, synthetic, and others) can be used as antigens in all those tests.³⁶⁵ For the diagnosis of CD, the WHO recommends two tests of different principles, either conventional or non-conventional.²,³⁸,⁶⁰,³⁶⁸

### 6.1.3. Interpretation of the Results

The combination of the results of the two tests enables the classification of the patient's serum as positive (two reagent tests) or negative (two non-reagent tests), considering concordant results of the two tests performed.³⁶⁹ Two positive tests indicate that the patient is seropositive, with detection of anti-*T. cruzi* antibodies by use of two different methodologies, meaning that the patient is infected with *T. cruzi*. When the result is non-reagent (two non-reagent tests of different principles), the serology is negative; in such cases, usually there is no epidemiology, and clinical manifestations, if present, can be explained by causes other than *T. cruzi* infection. In a third unusual possibility (< 5%

<footnote>*couplets/runs of ventricular extrasystoles. CCCD: chronic cardiomyopathy of Chagas disease; ECG: electrocardiogram; LVEF: left ventricular ejection fraction; HF: heart failure; NYHA: New York Heart Association, CMRI: cardiac magnetic resonance imaging.</footnote>
of the cases), the results are non-concordant, with a reagent test and another non-reagent (Figure 6.1).

Finally, in another possibility, one of the test's results is undetermined, that is, in the narrow range between negative and positive, the 'grey' region. An example is the passive transfer of antibodies from an infected mother to her child. The progressive decrease in the level of maternal antibodies in the non-infected offspring, around the third month of age, can correspond to that grey region, an undetermined result.³⁶⁹

In those rare situations of discordance, the clinician, after analyzing the epidemiological and clinical data, should assess if the patient underwent previous specific treatment and if there is any history of cutaneous leishmaniasis or other diseases, especially autoimmune ones. In such cases, a new blood sample should be collected. Usually, the discordant result becomes concordant in the new sample. If the result remains undetermined, the patient should be referred to a specialized service/laboratory, where other techniques will be performed for a conclusion to be reached. Exceptionally the referral laboratory will not reach a conclusion regarding the individual's infectious status, and parasitological methods can be used. In such cases, a clinical assessment with ECG should be performed. However, even in the presence of a normal EGC, the patient with an inconclusive serology should be instructed not to donate blood.

## 6.1.4. Special Situations

### 6.1.4.1. Inconclusive Serological Results

As already mentioned, inconclusive serological results are not usually found (< 5%), being often associated with the presence of other diseases, especially visceral or cutaneous leishmaniasis, systemic lupus erythematosus, and chronic liver diseases, usually with increased gamma globulin levels. These are the so-called cross reactions. Thus, other causes should be investigated, and the patient asked about any previous treatment with benznidazole. If affirmative, the individual's antibody levels might have decreased as a consequence of the treatment, turning the serology result undetermined.

### 6.1.4.2. Test Result Not Corresponding to Clinical Expectation

As already mentioned, two serological tests of different principles should be requested, preferably including the titles obtained, indicating the levels of antibodies. Usually both results are either positive or negative. Rarely the results of the two tests are discordant as follows: one negative and the other positive, or one positive and the other undetermined. In these situations, a new blood sample should be collected, using the same techniques and, if possible, a third one [for example, if ELISA is reagent and IIF is non-reagent, IHA or chemiluminescence immunoassay (CLIA) or ELISA with other antigens should be requested]. Usually, this procedure enables a conclusive result.

Several interferences can lead to a false reagent result, not confirmed by two other negative tests. In other cases, one test can be non-reagent while the same serum is reagent by

the other two tests. Clinical and epidemiological data usually lead to a diagnosis. In other circumstances, the clinical and epidemiological data may point to *T. cruzi* infection, while the serological tests are negative, requiring a new blood sample collection in a referral or specialized laboratory for new tests. According to such laboratories, when the results of three tests of different principles are negative, usually it is not *T. cruzi* infection. Thus, there are cases of RBBB due to other causes, and families with some members not infected by *T. cruzi* are often found, leading to the hypothesis of natural resistance to CD, already known in other infections, such as hanseniasis and tuberculosis. In addition, spontaneous cure, although rare, can occur. Exceptional cases of *T. cruzi* infection without the detection of serum antibodies have been reported.³⁷⁰ In such cases and if suspected, parasitological tests should be performed to solve the doubt.

### 6.1.4.3. Parasitemia

Although most chronic patients have low parasite load in peripheral blood, approximately 20% of them can have high parasitemia detected by serial multiplication tests (blood culture, PCR). In cases of RCD due to immunosuppression (HIV and others), most patients have high parasitemia. It is worth noting that "reactivation" means that the individual, from the laboratory viewpoint, is in the acute phase, defined by the detection of parasites in the peripheral blood on direct examination, which is only observed in a short period of the early acute phase and during reactivation itself in the chronic phase. Of note, the laboratory definition of the acute phase consists in the presence of viable parasites in peripheral blood.

### 6.1.4.4. Negative Serology in Patients in the Chronic Phase

Although possible, it is exceptional and has been reported in Bolivia.³⁷⁰

### 6.1.4.5. Spontaneous Cure

Spontaneous cure of CD has been reported by Zeledón et al.³⁷¹ after collecting blood from infected patients in Central America years after their acute phase, which had been duly registered with positive direct parasitological tests when no specific treatment was available. The rarity of spontaneous cure has been confirmed by a later study with 110 individuals in the chronic phase of CD, followed up for over 10 years, reporting that none of them showed further levels lower than the initial ones.³⁷² Nevertheless, the occurrence of spontaneous cure has been shown to be < 1%. Usually, in the second sample collection, some antibodies are always detected, meaning that their levels do not become totally negative. If they do, other hypotheses should be assessed, of which the most likely is difference between tests of distinct origins.

### 6.1.4.6. Acute Phase Diagnosis

Exceptional in Brazil nowadays, it is practically limited to cases of oral transmission through the ingestion of food contaminated with infected triatomines or their feces,
<figure><img src="image_5.png" /><figcaption>**Figura 6.1** - Flowchart for the serological diagnosis of Chagas disease. R: reagent; NR: non-reagent; U: undetermined. Note: Test 1: IIF or IHA or ELISA or chemiluminescence or electrochemiluminescence; Test 2: test different from test 1; Test 3: test with a different principle from test 1 and test 2.</figcaption></figure>

particularly in the Amazonian region (approximately 350 cases per year). Oral transmission currently represents the major cause of acute disease in several South American countries.¹¹⁴

In general, acute CD can be caused by triatomines (vector and oral transmission), contaminated blood transfusion or solid organ transplantation, vertical or congenital transmission, and laboratory accident. In a naturally or iatrogenically immunosuppressed individual, RCD is considered as acute

phase. In such cases, the laboratory diagnosis is made through the direct search of the parasite by use of parasitological methods including PCR.³⁷³

#### 6.1.4.7. Blood Services

The objective of blood services is to provide good-quality blood and, thus, they should use high-sensitivity tests, capable of detecting > 99% of infected samples. However, that
reasoning does not apply to the CD diagnosis. As a result of the necessary care to obtain blood with no infectious agent, the specificity can be lower (98%), leading to blood exclusion, but not necessarily meaning that a particular donor is infected. Frequently, when donating blood, an individual can be notified that he/she might be infected. In such circumstance, two serological tests of different principles should be requested, as already mentioned. Although, in the case series of referral services, 70% to 80% of the donors excluded are effectively infected, a significant proportion (20% to 30%) of those individuals will not be confirmed to have CD, reinforcing the need for a new blood collection and two serological tests.³⁷⁴

### 6.1.4.8. Congenital Transmission

Vertical (maternal-fetal) transmission represents the major *T. cruzi* transmission pathway in vector-free regions and in several endemic areas.⁵⁹ The prevalence rate of that type of transmission in Brazil is 1.7%, one of the lowest indices as compared to those of other South American countries.⁵⁷,⁸⁷ It is important to consider that babies with clinical signs suggestive of acute CD and born from women with chronic *T. cruzi* infection should undergo the diagnostic tests for infection as soon as possible. The early diagnosis of congenital CD is extremely important, because the trypanocidal treatment of infected babies in their first year of life leads to cure in 100% of the cases.

However, when the mother is infected with *T. cruzi* and no fetal infection occurs, the possibility of passing antibodies (IgG) from mother to fetus through the placenta during pregnancy should be considered. Thus, to detect congenital transmission, the parasitological diagnosis is recommended in the umbilical cord blood or in the newborn in the first 72 hours. Alternatively, in the absence of signs and symptoms of infection, the diagnosis can be made during the first months of life by use of direct parasitological methods (blood smear, microhematocrit, leukocyte cream, and PCR), with assessment of two or three samples to increase sensitivity.² Babies with negative initial parasitological tests should undergo serologic tests between 9 and 12 months of age, when maternal antibodies have disappeared. The persistence of unchanged anti-*T. cruzi* antibody titles in children from the age of 9 months on indicates congenital infection, while absence of those antibodies at that time rules out the possibility of infection in the child.²

### 6.1.4.9. Serology of Infected Individuals Treated with Chemotherapy Drugs

The follow-up of patients by use of laboratory tests after specific treatment of the infection is approached with more details in the chapter regarding chemotherapy for the disease in general. Here, for those looking for support to exclude or confirm the diagnosis, it is worth noting that it is a very sensitive and complex subject to be reduced to a few principles. According to J. R. Cançado, "it is obvious that, if an infected individual has antibodies and parasites, both need to disappear so that the individual can be considered cured (after chemotherapy)". This precept applies to treated individuals in the acute phase (70% of cure) in a period of months, as

well as to children receiving the trypanocidal treatment in the chronic but recent phase, confirming a negative serology (ELISA with recombinant antigens) in 58% to 62% of the cases after 3 to 4 years of follow-up.³⁷⁵,³⁷⁶ In addition and to a smaller proportion (25%), patients treated in the late chronic phase showed a negative serology only decades after undergoing treatment. This relates to the duration of the parasite-patient coexistence (weeks, years, decades).³⁷⁷⁻³⁸¹ The analysis of the cure should be based on negative serological tests or even on the reduction (as long as significant) of antibody levels, preferably with diagnostic tests using non-purified antigens.

### 6.1.4.10. Rapid Serological Tests

Rapid diagnostic tests are typically easy to handle and do not require a reference laboratory for specialized diagnosis as compared to the classical serological techniques. Several types of rapid tests are available for the diagnosis of CD. Many can be performed on serum or peripheral blood and stored at room temperature for long periods of time. Their use is indicated in endemic areas, mainly in field research (serological and epidemiological inquiries), because they contribute to increase access to diagnosis. However, despite being used for that purpose, the rapid tests for CD are not usually recommended as an independent diagnostic method by the WHO, because of their low sensitivity.³⁸²

### 6.1.4.11. Parasitological Tests

Parasitological tests should be requested in special situations, not routinely. There are several types of parasitological tests for the chronic phase of CD, which, because of low parasitemia, are aimed at promoting the multiplication of the few parasites present by use of blood culture, xenodiagnosis, inoculation in experimental animals, or identification of nucleic acids (DNA or RNA) specific to the protozoan parasite, using the PCR technique.

The multiplication of the parasites can take several weeks; thus, the result can take time. It involves "in house" techniques, which require special conditions (reagents, insectary, *bioterium*), as well as highly-qualified individuals. Usually, those techniques are performed only at specialized research centers. Blood culture and xenodiagnosis used in the chronic phase have low and variable sensitivities (approximately 20%); when repeated, the probability of detection can be increased, reaching up to 60% of sensitivity.³⁶⁵,³⁶⁸,³⁶⁹,³⁸³ For some patients with very low parasitemia, even successive tests will yield persistently negative results.

In the PCR method, the identification of part of the parasite's genetic material requires less time (hours), but special reagents and technical conditions are also needed. Because of its importance, the PCR technique is detailed below.

#### 6.1.4.11.1. Indications for Parasitological Tests, particularly Polymerase Chain Reaction

One of the major indications for parasitological tests is the follow-up of patients treated with benznidazole or other chemotherapy drugs. Accurate diagnostic methods and reliable markers of the response to the parasiticide treatment
are priorities in the research and resource development in general for application in CD.³⁸⁴ PCR has been valued for patients' assessment and monitoring when a positive PCR result for the parasite genetic material by the end of the trypanocidal treatment indicates therapeutic failure.³⁸⁵ However, after treatment, a negative PCR result does not indicate cure of the infection. It is worth noting that the negative serological conversion in treated chronic patients who respond favorably to treatment may take years.³⁸⁶ The PCR can indicate in advance therapeutic failure, evidencing resistance to the trypanocidal treatment and therapeutic ineffectiveness.

In addition, in cases of RCD, PCR is useful, enabling the early detection of reactivation. Monitoring RCD in immunosuppressed individuals is an area of increasing interest. The RCD in infected patients in the chronic phase who acquire HIV or during immunosuppressive therapies, after organ transplantation, autoimmune diseases or cancer, usually increases parasitemia, characterizing acute CD.³⁸⁷⁻³⁸⁹ In cases of immunosuppression resulting from CTX, the exclusion of rejection and the detection of RCD can be done early by use of PCR performed in peripheral blood samples and endomyocardial biopsy.³⁹⁰⁻³⁹²

### 6.1.4.11.2. Interpretation of the Results of Parasitological Tests

By definition, parasitological tests can only be valued if positive, showing the presence of parasites or their amplified structures (PCR). A negative test, per se, has no value, because the result is only valid for the sample collected. Another sample collected on another day can be positive. Thus, a negative parasitological test does not mean that the individual is not infected by *T. cruzi* nor that the infection has been cured.

### 6.1.4.12. Polymerase Chain Reaction

Since the 1990s, PCR has been used as a supportive molecular method for the diagnosis of patients in the chronic phase of CD, because of its higher sensitivity as compared to that of parasite multiplication tests (blood culture and xenodiagnosis) and its high potential for use in trypanocidal chemotherapy monitoring.³⁹³⁻³⁹⁶

Several studies have shown positive PCR results in 40% to 70% of chronic patients previously diagnosed by use of conventional serology. This variability in positivity depends on several factors, such as parasite load, volume of the blood collected, blood sample for DNA isolation, DNA purification method, target region to be amplified, characteristics of the populations studied, as well as the high genetic diversity observed in the parasite DTU.³⁹⁷⁻⁴⁰¹

Different combinations of molecular targets, sets of reaction initiators, extraction methods, and DNA amplification platforms have been used to assess the accuracy of the method in peripheral blood samples of patients with chronic CD. Usually, the diagnostic sensitivity is lower as compared to that of serological tests.⁴⁰¹ For those patients, molecular-based detection methods have a limited diagnostic value, because their sensitivity is significantly lower than that of serological tests.⁴⁰⁰,⁴⁰²

It is worth noting that a positive PCR result confirms the parasite's presence in a certain sample; however, because of parasites' scarcity and intermittent circulation, which characterize the chronic phase, a negative PCR result does not exclude infection.³⁹⁸ Nevertheless, in case of positive samples, the PCR enables the characterization of the *T. cruzi* infectant DTU directly in the patient's blood, not requiring the parasite's previous isolation.

For selecting the molecular target to detect the *T. cruzi* genetic material, the following is recommended: the use of conserved DNA sequences (present in all genetic lineages of the parasite), which are exclusive of *T. cruzi* (specificity); and these sequences should be represented in multiple copies in the genome (higher sensitivity). The most often used targets in conventional PCR (qualitative) have been the DNA from the kinetoplasts or kDNA (mitochondrial genome) and the repeating units (satellite DNA) present in the nuclear genome.⁴⁰²

The real time or quantitative PCR (qPCR) can determine the parasite load by quantifying specific DNA sequences. For the quantification assays, satellite DNA sequences are preferably used, because of their smaller variability in the number of copies between the different genetic lineages of *T. cruzi* as compared to the kDNA minicircles.⁴⁰³

### 6.1.4.13. Operational Procedures for PCR Use

1. Blood collection: 10mL of peripheral blood (minimum of 5mL) are usually collected in tubes with EDTA (any other anticoagulant inhibits the enzyme of the reaction). The blood is immediately transferred to a tube containing the same volume (1:1) of a lysis buffer for sample preservation, the 6M guanidine hydrochloride - 0.2M EDTA solution (pH 8.0).

2. Sample processing: the blood in the guanidine solution is boiled in water bath (100°C, 15 min) to promote a homogeneous distribution of the parasite's target DNA sequences, enabling DNA extraction from a lower sample volume (300 µL). The boiled material remains at room temperature for 48 to 72 hours and can undergo DNA extraction. The remaining material is stored in the refrigerator or cold chamber, without freezing.

3. Two 300-µL copies undergo DNA extraction using commercial kits based on purification through silica minicolumns, according to the manufacturer's recommendations.

4. The PCR protocols follow those standardized in-house by the laboratories, usually based on the international consensus description.⁴⁰²

5. For qualitative PCR, the test result is the visualization of the amplified product (of the kDNA or satellite DNA) from the agarose gel electrophoresis stained with fluorescent agents that intersperse with DNA.

6. For qPCR, the protocols also follow the international consensus⁴⁰³ and require the inclusion, in each assay, of standard samples with preestablished concentrations of parasites (parasite equivalent per reaction), which serve as calibrating samples for the absolute *T. cruzi* quantification. The results generated in qPCR are visualized in real time as
graphs issued by the equipment, without requiring running an electrophoresis.

7. The use of positive (DNA extracted from cultivation of *T. cruzi* cells) and negative (DNA extracted from blood known to be non-infected and a tube containing ultrapure water without DNA) controls is highly recommended.

8. In cases with negative PCR in qualitative assays, DNA extraction should be repeated in two other samples of blood in guanidine (300 µL) for the new PCR test directed to some human gene (β-globin, β-actin, etc). This is a decisive step to exclude false-negative results due to the presence of inhibitors in blood samples or the loss or poor quality of the DNA extracted.

9. Recently, a diagnosis kit for PCR produced by the FIOCRUZ (Bio-Manguinhos) has been made available and approved by the sanitary authorities, which will facilitate its use in the Public Health Central Laboratories (LACEN).

## 6.2. Diagnostic Methods for Structural and Functional Cardiac Abnormalities

Table 6.1 shows the additional tests used in the diagnosis of cardiomyopathy in individuals with suspected or confirmed CD. In addition, it shows the strength of each recommendation and its level of evidence. For some tests, in addition to their diagnostic extent, their prognostic connotation is added.

### 6.2.1. Electrocardiogram in Chagas Disease

The ECG is the most important initial cardiovascular test to assess patients with CD, enabling the classification of its clinical forms.³³⁰,⁴⁰⁴ Thus, well-defined electrocardiographic changes in the infected individual indicate the presence of cardiomyopathy.³³⁴ The most frequent and defined alterations are atrioventricular conduction blocks, right bundle branch and left anterosuperior fascicle blocks, ventricular repolarization alterations, and ventricular ectopic beats. Almost all electrocardiographic abnormalities can be found in CD, in which cardiac electric activity formation and conduction alterations predominate.

Complete or incomplete RBBB is the most common conduction disorder in CD, found in 10% to 50% of infected patients, depending on the characteristics of the sample studied.³³⁰,⁴⁰⁴,⁴⁰⁵ RBBB is frequently associated with LAFB, the most commonly found combination in CCCD. Left bundle branch block (LBBB) is rare and of worse prognosis.

Atrioventricular blocks are common, of varied degrees, and can be the first manifestation of the disease. Advanced AVBs result from extensive lesions of the atrioventricular node and His-Purkinje system, can progress with syncope and need for definitive PM implantation, predisposing to sudden death from asystole.

Sinus node dysfunction frequently expresses as bradycardia and can cause episodes of sinoatrial block and sinus arrest. Sinus node dysfunction accompanied by symptoms of reduced cerebral blood flow characterizes sinus node disease, which, in some patients, typically alternates bradycardia and tachycardia episodes.

Atrial fibrillation in CCCD is a late alteration, found in up to 5% of the ECG tracings.³³⁰,³³²,⁴⁰⁴ Usually, AF is associated

with a more pronounced and extensive myocardial damage, diffuse involvement of the conduction system, ventricular arrhythmias, and stroke.

Ventricular arrhythmias, such as polymorphic VE and ventricular tachycardia (VT), are predictors of syncope and sudden cardiac death due to VF. Pathological Q waves and loss of R wave progression from V1 to V3-V4 indicate inactive electrical areas and result from myocardial fibrosis. Diffuse conduction disorders and low QRS voltage are usually associated with marked ventricular dysfunction.³³²

Association of two or more abnormalities in the same electrocardiographic tracing is one characteristic of severe cardiopathy. Conduction disorders associated with ventricular arrhythmias are the most frequent. Coexistence of pathological Q waves indicates more significant impairment of ventricular function. Thus, the higher the number of electrocardiographic changes, the worse the prognosis.

Traditional epidemiological studies, assessing electrocardiographic changes in CD, have been conducted predominantly with individuals infected through classical vectorial transmission and included younger individuals.³³⁴,⁴⁰⁴ With the current more comprehensive control of vectorial transmission and the *T. cruzi*-infected population aging, chronic diseases, such as hypertensive and ischemic heart diseases, can coexist with CCCD and the typical abnormalities of these conditions can overlap the typical ones of CD.³³² In addition, although there are typical abnormalities of CCCD, they are neither specific of that condition nor appear in all cases.

Regarding the relationship between electrocardiographic changes and prognosis, recent investigations by independent groups of researchers have highlighted the potential contribution of the analysis of those changes, using artificial intelligence and machine learning resources, to predict ventricular dysfunction and myocardial fibrosis, two fundamental prognostic factors in CD.⁴⁰⁶,⁴⁰⁷

When CD diagnosis is suspected or confirmed, ECG should be performed and repeated regularly to assess the appearance or progression of abnormalities. In individuals with normal ECG, new changes indicate progression to the cardiac form, requiring additional tests.⁵,⁷ For patients with symptoms suggestive of cardiac arrhythmias, such as palpitations, syncope, and recovery from sudden death, an ECG at rest is mandatory before performing new tests, such as Holter, stress ECG, or intracardiac electrophysiological study (EPS).

### 6.2.2. Chest Radiography

Considering its large availability, chest X-ray is one of the most used tests to diagnose cardiovascular impairment, and mainly to assess pulmonary congestion. Even in symptomatic patients, an enlarged cardiac area with little congested pulmonary fields is often found. In addition, RV enlargement signs on posteroanterior and lateral projections are common and significant, and signs of right pleural effusion secondary to systemic congestion can be found. An increased CTI is an independent predictor of death in individuals with CCCD.⁴⁰⁸ A recent study has shown that the presence of cardiomegaly based on the CTI can be properly identified by an increased LVDD, measured on ECHO.³³⁷
<table><caption>Table 6.1 – Additional methods for the diagnosis and prognosis of chronic cardiomyopathy of Chagas disease (CCCD)</caption><thead><tr><th>Tests</th><th>Recommendation grade</th><th>Level of evidence</th></tr></thead><tbody><tr><td><strong>12-lead Electrocardiogram</strong></td><td></td><td></td></tr><tr><td>Initial diagnostic and prognostic assessment of every individual with positive serology for Chagas disease</td><td>Strong</td><td>B</td></tr><tr><td>Annual (ECG with specific changes*) or biannual (normal ECG or with unspecific changes) repetition for assessment of progression and prognosis</td><td>Strong</td><td>C</td></tr><tr><td>Repetition at any time in the presence of changes in clinical findings</td><td>Strong</td><td>C</td></tr><tr><td><strong>Chest X-ray</strong></td><td></td><td></td></tr><tr><td>Initial diagnostic and prognostic assessment of every individual with CCCD</td><td>Strong</td><td>B</td></tr><tr><td>Clinical evidence of pulmonary or systemic congestion</td><td>Strong</td><td>B</td></tr><tr><td><strong>Exercise or cardiopulmonary test</strong></td><td></td><td></td></tr><tr><td>Initial diagnostic and prognostic assessment of every individual with CCCD</td><td>Conditional</td><td>C</td></tr><tr><td>Presence of symptoms, such as chest pain, palpitations, syncope, or presyncope related to physical exertion, or dubious, or of unknown origin</td><td>Strong</td><td>B</td></tr><tr><td>Periodical assessment of implantable devices for programming optimization and assessment of physical capacity</td><td>Conditional</td><td>C</td></tr><tr><td>Cardiopulmonary test for functional assessment, risk stratification, and support for cardiac transplantation indication in advanced HF</td><td>Strong</td><td>B</td></tr><tr><td><strong>24-hour Holter</strong></td><td></td><td></td></tr><tr><td>Initial diagnostic and prognostic assessment of every individual with CCCD</td><td>Strong</td><td>B</td></tr><tr><td>Investigation of symptoms, such as palpitation, presyncope, and syncope</td><td>Strong</td><td>B</td></tr><tr><td>Follow-up of patients with complex ventricular arrhythmias and assessment of antiarrhythmic drug therapy</td><td>Conditional</td><td>C</td></tr><tr><td>Follow-up of patients with sinus node dysfunction or potentially risky AV/IV conduction disorders</td><td>Conditional</td><td>C</td></tr><tr><td>Follow-up of individuals with implantable cardiac devices (PM, ICD, CRT)</td><td>Strong</td><td>C</td></tr><tr><td><strong>Intracardiac electrophysiological study</strong></td><td></td><td></td></tr><tr><td>Assessment of syncope (or unquestionable presyncope) and suspicion of brady- or tachyarrhythmia, when noninvasive tests are inconclusive</td><td>Strong</td><td>B</td></tr><tr><td>Differential diagnosis of wide QRS complex tachycardia and uncertain diagnosis</td><td>Conditional</td><td>C</td></tr><tr><td><strong>Conventional echocardiography</strong></td><td></td><td></td></tr><tr><td>Initial diagnostic and prognostic assessment of every individual with CCCD</td><td>Strong</td><td>B</td></tr><tr><td>Suspicion of CCCD based on history, clinical examination, or electrocardiographic changes</td><td>Strong</td><td>B</td></tr><tr><td>When HF symptoms aggravate or in the presence of syncope, arrhythmic events, stroke, or peripheral thromboembolism</td><td>Strong</td><td>B</td></tr><tr><td>Periodical reassessment** regardless of the presence of global or regional systolic dysfunction on previous test</td><td>Conditional</td><td>C</td></tr><tr><td>Assessment of individuals with normal ECG and suggestive symptoms of CCCD</td><td>Conditional</td><td>C</td></tr><tr><td><strong>Nuclear medicine (radionuclide ventriculography)</strong></td><td></td><td></td></tr><tr><td>Assessment of ventricular function, especially the right ventricle, in addition to echocardiography, as an alternative to magnetic resonance imaging</td><td>Conditional</td><td>C</td></tr><tr><td>Identification of regional contractility defects, when echocardiography is technically inappropriate, as an alternative to magnetic resonance imaging</td><td>Conditional</td><td>C</td></tr><tr><td><strong>Nuclear medicine (myocardial perfusion)</strong></td><td></td><td></td></tr><tr><td>Initial assessment of individuals with CCCD and chest pain</td><td>Conditional</td><td>C</td></tr><tr><td>Additional assessment and detection of microvascular defects in individuals with chest pain and angiographically normal coronary arteries</td><td>Conditional</td><td>B</td></tr></tbody></table>
# Guidelines

<table><thead><tr><th colspan="3">Nuclear medicine (sympathetic innervation assessment)</th></tr></thead><tbody><tr><td>Additional method for the assessment of complex ventricular arrhythmias</td><td>Conditional</td><td>C</td></tr><tr><th colspan="3">Cardiac magnetic resonance imaging</th></tr><tr><td>In the suspicion of concomitance of CCCD and coronary artery disease or other non-ischemic cardiomyopathy and to assess the etiology and extesion of myocardial fibrosis</td><td>Conditional</td><td>B</td></tr><tr><td>Morphological and functional, global and segmental assessment and search for thrombi, as an alternative to echocardiography with technical limitations</td><td>Conditional</td><td>B</td></tr><tr><td>When there is no initial clinical suspicion of Chagas disease (nonendemic area), CMRI can favor an extremely probable diagnosis of CCCD based on the late enhancement pattern and motivate the performance of serological tests to confirm the etiological diagnosis</td><td>Conditional</td><td>C</td></tr><tr><td>Discordance between symptoms and degree of ventricular dysfunction in the context of ambiguous indication of procedures, such as ICD implantation</td><td>Conditional</td><td>C</td></tr><tr><td>Planning of electrophysiological studies with possible RF ablation (to guide the local of ablation) or device implantation to define if resynchronization therapy should or not be added (extensive lateral and/or septal fibrosis is considered a relative contraindication because it increases the rate of nonresponders)</td><td>Conditional</td><td>C</td></tr><tr><th colspan="3">Computed tomography</th></tr><tr><td>Assessment of coronary anatomy in patients with CCCD and high probability of obstructive coronary artery disease</td><td>Conditional</td><td>B</td></tr><tr><td>Characterization of normal myocardium/fibrosis on late enhancement as an alternative to CMRI</td><td>Conditional</td><td>C</td></tr><tr><td>Assessment of biventricular systolic function in addition to echocardiography in patients with contraindication to CMRI</td><td>Conditional</td><td>C</td></tr><tr><th colspan="3">Cardiac catheterization</th></tr><tr><td>Assessment of coronary anatomy in patients with CCCD and high probability of obstructive coronary artery disease</td><td>Strong</td><td>B</td></tr><tr><td>Assessment of pulmonary vascular resistance in candidates for cardiac transplantation with noninvasive evidence of pulmonary hypertension</td><td>Conditional</td><td>B</td></tr></tbody></table>

## 6.2.3. Echocardiography

Echocardiography is the most used imaging test for the initial assessment and follow-up of patients with CD.³³⁹ The echocardiographic signs can vary from localized alterations in segmental contraction in the initial stages of cardiopathy to important dilation of cardiac chambers with biventricular dysfunction in more advanced stages. The presence and severity of the alterations on ECHO, in association with clinical data, are criteria used for the classification of CD in stages A to D, with an intrinsic prognostic value, as mentioned in another chapter of this guideline.

### 6.2.3.1. Left Ventricular Systolic Function

The DCM of CD is characterized by LV enlargement and segmental and/or diffuse hypokinesia, and LV systolic dysfunction is the most important predictor of death.⁴⁰⁸ Because of the presence of geometrical and segmental alterations, M mode is not recommended for assessing LV dimensions and systolic function. Those should be analyzed preferably by using two-dimensional mode and estimation of volumes, with

the biplanar method (Simpson). As in other cardiomyopathies, three-dimensional ECHO is superior to two-dimensional ECHO for assessing volumes and ejection fraction, mainly in suspected LV foreshortening in apical view or in the presence of segmental contraction abnormalities with distortion of the suspected geometry, such as in aneurysms frequently identified with the method.

Speckle tracking ECHO enables the early diagnosis of systolic dysfunction by assessing myocardial deformation in patients with CD. Several studies have assessed systolic deformation, in the longitudinal, radial, and circumferential axes, of patients with the IFCD or cardiopathy. The most consistent results have assessed GLS, as in other nonischemic cardiomyopathies. Even in patients in the earliest stages of cardiopathy, as those with preserved ejection fraction (stage B1) or those with the IFCD (stage A), regional alterations in myocardial deformation are observed. In patients with the IFCD, the regional alterations identified on STE occur mainly in the LV inferior and inferolateral segments.³¹³,⁴⁰⁹,⁴¹⁰ The prognostic value of those early regional alterations in patients with the IFCD has not been defined. A recent study, including 144

<footnote>*Mainly when multiple: complete right bundle branch block, especially associated with left anterior fascicular block (LAFB), frequent ventricular extrasystoles, pathological Q waves or electrical inactive areas, second-degree (Mobitz 2) or third-degree atrioventricular block (AVB), and atrial fibrillation; †Mainly when isolated: isolated LAFB, sinus bradycardia, first-degree AVB, low-voltage QRS complex on peripheral leads, and nonspecific abnormalities of the ST-T segment. HF: heart failure; AV: atrioventricular; IV: intraventricular; PM: pacemaker; ICD: implantable cardioverter-defibrillator; CRT: cardiac resynchronization therapy.</footnote>

<footnote>**3 to 5 years for cases with preserved ejection fraction and no segmental contractility change on previous echocardiogram; 1 to 2 years for cases with global (even mild) or segmental left ventricular dysfunction. HF: heart failure</footnote>

<footnote>CCCD: chronic cardiomyopathy of Chagas disease; ICD: implantable cardioverter-defibrillator; CMRI: cardiac magnetic resonance imaging; RF: radiofrequency.</footnote>
patients with CD, but without evidence of cardiac impairment, has shown that the radial strain assessed on STE was a predictor of the development of cardiomyopathy.⁴¹¹ In patients with reduced LVEF and CCCD or idiopathic DCM, reduced GLS was a predictor of combined outcomes regardless of the LVEF.⁴¹²

### 6.2.3.2. Segmental Changes in Ventricular Contractility

Segmental changes can be present in 10% of patients in the CD's early stage and in up to 50% in the presence of dilatation and systolic dysfunction. These regional wall motion abnormalities, when incipient, identify individuals at risk for progressing to global ventricular dysfunction and arrhythmias.³⁴¹,⁴¹³ In patients with CCCD, an altered segmental motion score at rest (≥ 1) could identify those at higher risk for clinically relevant outcomes, such as global mortality, despite the initially preserved global ventricular function.³⁴² Segmental alterations are most frequently found in the inferior and inferolateral walls, in addition to the apical segments. The regional pattern of impairment, not related to the coronary territory, is characteristic of this cardiomyopathy.

Ventricular aneurysms vary in size and shape, from small finger-like ("glove finger") to large apical ("saccular") aneurysms, which can be hard to differentiate from those found in ischemic cardiopathy.³³⁹ The mean prevalence of apical aneurysm in different echocardiographic series was 8.5% (ranging from 1.6% to 8.6%) in asymptomatic patients or those with mild cardiopathy and up to 55% (ranging from 47% to 64%) in patients with moderate to severe LV systolic dysfunction.³³⁹ The aneurysms are not restricted to the apex or inferolateral wall, and can be found in the septum, anterolateral wall, and right ventricle.³⁴⁰ Intraventricular thrombi can be associated with those aneurysms, being considered important risk factors for embolic events.

Although transthoracic ECHO at rest is fundamental in the CCCD assessment because it enables the identification of segmental alterations, mainly apical aneurysms, its execution can be technically challenging. The use of deep breath and non-conventional echocardiographic views, such as the intermediate between the apical 4- and 2-chamber views, with posterior angulation of the transducer, can be necessary, as well as the complementary use of ultrasound contrast imaging.

### 6.2.3.3. Left Ventricular Diastolic Function

The alteration in myocardial relaxation is the first to appear, and can be present even in patients with the IFCD. As the cardiomyopathy progresses, the diastolic dysfunction can worsen and show a typical restrictive pattern.⁴¹⁴,⁴¹⁵ The diastolic function analysis can be challenging because of confounding factors, resulting from the occasional presence of AF and PM in the right chambers. The gradual increase in the E/e' ratio occurs from the IFCD and a value greater than 15 is a predictor of worse outcome in patients with mild to moderate systolic dysfunction.⁴¹⁶ There is evidence that the E/e' ratio correlates independently with serum levels of brain natriuretic peptide (BNP).⁴¹⁷

Diastolic dysfunction contributes decisively to atrial remodeling, whose volume can be increased in any

stage of the CCCD.⁴¹⁸ The left atrial volume correlates independently with mortality.³⁴²,⁴¹⁵,⁴¹⁹ Left atrial function in CCCD is more impaired than in other etiologies, such as idiopathic DCM, probably because of the associated intrinsic atrial myopathic impairment.⁴²⁰ When assessed by use of strain, the left atrial function also was an independent predictor of clinical events in patients with CD.⁴¹⁸ Similarly, left atrial dysfunction indices assessed on three-dimensional ECHO and by strain were independent predictors of recent-onset AF in those patients' follow-up.⁴²¹

### 6.2.3.4. Right Ventricular Assessment

Right ventricular assessment on conventional ECHO, using dedicated projections, allows the quantification of RV dimensions, volumes (three-dimensional ECHO), and contractile function, and should be performed in all patients with CCCD. Although frequently associated with LV dysfunction,³⁴⁸ RV impairment more rarely can occur primarily and prematurely as compared to LV impairment.³⁴⁵ The RV systolic dysfunction, assessed by use of conventional echocardiographic parameters, such as Tei index, was an independent predictor of poor prognosis in CCCD.³⁵⁰ The RV systolic function analysis by use of STE, especially in the chamber's free wall, showed satisfactory accuracy, correlating with other methods, such as CMRI.³⁴⁷ In addition, three-dimensional ECHO is a promising tool to assess RV systolic function.

### 6.2.3.5. Stress Echocardiography

Pharmacological stress (and possibly exercise stress) ECHO can show the two-phase contractile reserve in those patients, who typically have no subepicardial coronary artery obstruction.⁴²² Although the pharmacological test usually uses dobutamine, which has an arrhythmogenic potential, the method proved safe in CCCD, and an altered segmental contraction index at rest is an independent predictor of arrhythmias during the test.⁴²³

### 6.2.4. Cardiac Magnetic Resonance Imaging

Although CMRI is not a test for the initial assessment of CD, the method has proven useful for CCCD diagnosis and risk stratification. Patients undergoing investigation of cardiomyopathy with no specific suspicion of CD and not residing in an endemic area frequently do not undergo serological tests for CD. In such cases, a typical global or regional systolic dysfunction pattern associated with a specific myocardial fibrosis pattern and location on CMRI can raise the suspicion and indicate the need for the specific serological test.

In addition, CMRI can estimate the prognosis. The amount of myocardial fibrosis strongly correlates with markers of disease severity, ventricular arrhythmias, severe cardiovascular events, and even death.³¹¹,⁴²⁴ In addition, CMRI can be useful to detect early myocardial involvement in CD, mainly in the IFCD, when all other tests are usually normal.³¹⁰,³¹¹

On CMRI, new noninvasive tools can identify myocardial inflammatory activity (edema and myocardial hyperemia) at an early stage before the development of irreversible lesions,
# Guidelines

such as necrosis and fibrosis, and aid risk stratification and even therapeutic decision-making.<sup>310,425</sup>

The CMRI can be useful to detect intracardiac thrombi in certain patients, especially those with limited echocardiographic images and no indication for invasive angiocardiography.<sup>310,311,426,427</sup>

Recent investigations have shown that CMRI has a good potential to assess the prognosis of patients with CCCD, independently of that provided by the RASSI score, allowing the re-stratification of those at low to intermediate risk of death.<sup>428,429</sup> The prognostic potential of CMRI in CCCD will much likely depend on confirmation by on-going studies and should corroborate the expansion of the already used risk stratification methods.<sup>430</sup>

The CMRI should include biventricular systolic function assessment through SSFP (steady-state free precession) techniques, T2-weighted images and/or T2 mapping for the assessment of myocardial edema, in addition to the mandatory use of late gadolinium enhancement to detect gross regional myocardial fibrosis. In addition, the pre-(native) and post-contrast myocardial T1 mapping technique should be included to calculate the myocardial extracellular volume, which is a measure of interstitial and diffuse fibrosis that can be present in this cardiomyopathy, even in myocardial regions with no evident late enhancement. The global pre- and post-contrast T1-weighted enhancement (rapid spin-echo acquisition, similarly to the Lake Louise criterion, originally for viral myocarditis) or the early gadolinium enhancement can be useful to detect hyperemia/inflammation. In addition, long inversion time late gadolinium enhancement (~ 600ms) should be used, specifically in suspected intracavitary thrombus, to increase the sensitivity of its detection.

To assess mitral or tricuspid regurgitation, usually present in advanced CCCD, cine magnetic resonance imaging (MRI) and phase contrast cine MRI (mapping sequence) are used.

It is worth noting the classical example of CCCD on CMRI, which involves the basal and medial inferolateral segments and the LV apex, with typical contractile changes on cine MRI and characteristic myocardial fibrosis pattern and distribution on late enhancement. A typical finger-like LV apical aneurysm can be clearly seen on cine and late enhancement MRI.

Recent scientific position statement on CD of the American Heart Association has recommended CMRI in certain patients with cardiopathy to assess the fibrosis extension and even serial CMRI for individuals with complex ventricular arrhythmias, especially NSVT.<sup>7</sup>

Another consensus document on imaging in CD of the European Association of Cardiovascular Imaging and the SBC Cardiovascular Imaging Department has recommended that CRMI should be indicated for certain patients with severe ventricular arrhythmias to quantify the extension of myocardial fibrosis and assess the risk of sudden death with potential impact on the indication for an implantable cardioverter-defibrillator (ICD). In addition, CMRI should be indicated for the assessment of LVEF when 2-D ECHO is considered unsatisfactory and contrast or three-dimensional ECHO is not available.

## 6.2.5. Nuclear Medicine

Nuclear medicine is a noninvasive imaging modality but requires the use of radiation. In CD, it can be used to assess biventricular function as an alternative to CMRI and to analyze myocardial perfusion when stenotic epicardial or microvascular coronary artery disease is suspected, in addition to assessing cardiac sympathetic innervation.<sup>205</sup>

### 6.2.5.1. Radionuclide Ventriculography

Nuclear medicine is an option for the analysis of the systolic function of both ventricles, especially in patients with contraindication to CMRI and in the rare cases in which ECHO cannot be technically performed. Radionuclide ventriculography could be considered the gold-standard method for measuring the ejection fraction of both ventricles because it allows integrated sampling of several cardiac cycles. Therefore, it minimizes the occasional variability that limits, in some circumstances, the reliability of the methods that analyze only a few cycles. In addition, radionuclide ventriculography is used to determine the diastolic and systolic volumes without resorting to geometrical assumptions, as well as to provide information on regional contractility and the presence of ventricular aneurysms, characteristic of CD.

Radionuclide ventriculography can be used, with limitations, to assess diastolic function, whose alteration can be one of the earliest manifestations of CD. In addition, RV dysfunction, which can also be an early sign of CCCD, can be accurately assessed with nuclear medicine techniques, whose use in patients with CCCD, however, is still logistically limited.<sup>205,431</sup>

### 6.2.5.2. Myocardial Perfusion

The prevalence of obstructive coronary artery disease is not usually high among patients with CCCD, even in the presence of precordial pain. However, several researchers have independently reported coronary microcirculation dysfunction in those patients, and the presence of perfusion defects have prognostic value, because they can precede the development of myocardial contractile dysfunction.

The presence of scintigraphic changes in patients with CCCD can translate the inflammatory mechanism through which, at least partially, the cardiac muscle is destroyed in CCCD and replaced by fibrous tissue. Myocardial perfusion imaging by single-photon emission computed tomography (SPECT) is effective in detecting cardiac muscle perfusion disorders, even when lesions in epicardial coronary arteries are absent.<sup>182</sup>

With lower logistic availability, PET/CT is an alternative test to study inflammatory and perfusion alterations, as well as myocardial viability loss or preservation, in ventricular areas that show contractile deficit, being a suitable test for microcirculation study.<sup>431</sup>

### 6.2.5.3. Sympathetic Innervation Assessment

Depression of the myocardial sympathetic innervation occurs at the ventricular level early in CD and maybe at higher
intensity than in other heart diseases. This can be associated
with the loss of reflex autonomic control and even precede
any other cardiac impairment. Nuclear medicine, by use of
I-MIBG scintigraphy,¹²³ enables the detection of ventricular
sympathetic innervation defects, especially in the inferior,
posterolateral, and apical walls, long before any contractile
defect in those segments appears.¹⁸³ These myocardial
innervation alterations might be associated with a higher risk
for SVT and worse prognosis.²⁰⁵,²⁰⁸

6.2.6. Computed Tomography of Coronary Arteries

Computed tomography of coronary arteries, similarly to
invasive angiocardiography based on cardiac catheterization,
uses ionizing radiation and iodine contrast medium, being
primarily used for the noninvasive study of coronary anatomy
in several clinical contexts.

In CD, the experience with this approach in clinical practice
is limited and applies to patients with contraindication to other
imaging methods, such as CMRI and myocardial scintigraphy,
in whom the echocardiographic study shows technical
limitations. ⁴³² Computed tomography of coronary arteries in
general is more indicated when the probability of obstructive
subepicardial coronary artery disease is low but should be
ruled out in patients with CCCD and atypical precordial pain.

Preliminary experience with the method has shown
that Brazilian patients with CD have a reduced prevalence
of obstructive subepicardial coronary artery disease,
thus corroborating older evidence supported by invasive
angiographic studies.²⁶⁹

6.2.7. Ambulatory Electrocardiography (Holter)

The pathogenesis of CCCD is complex and multifactorial,
includes tissue damage by the parasite and exacerbated
immune response, leading to inflammatory reaction,
autonomic nervous system involvement, and microcirculation
impairment. The result of these pathogenetic mechanisms
is cell necrosis and their replacement by localized areas of
myocardial fibrosis.

The zones of fibrosis have predilection for the conduction
system (sinus node, atrioventricular node, and His-Purkinje
system branches and fascicles),⁴³³ being usually a primordial
manifestation of cardiac involvement. The combination of areas
of fibrosis, autonomic dysfunction, and conduction system
impairment favors the occurrence of both bradyarrhythmias
and tachyarrhythmias, sometimes before cardiac structural
alterations are detected on imaging tests, such as ECHO. This
early manifestation of arrhythmias in CCCD characterizes the
disease as an arrhythmogenic cardiomyopathy,⁴³⁴ whose first
clinical manifestation can be sudden death.³⁵³ In fact, sudden
cardiac death is the major cause of death in CCCD, accounting
for approximately 60% of the deaths.³⁵²

The detection of cardiac arrhythmias on Holter or during
exercise testing is an essential part of the routine assessment
of patients with CCCD, enabling the diagnosis of sinus
node dysfunction, atrioventricular conduction disorders,
supraventricular tachyarrhythmias and ectopic beats,
ventricular ectopic beats, and NSVT or SVT.

A study assessing the occurrence of ventricular ectopic
beats on Holter in patients with CCCD has shown that the
apparently random behavior of that arrhythmia in 24-hour
recordings disappears when longer periods, of 7 days, are
analyzed, suggesting that longer Holter recordings would be
more suitable in this context. 435

The presence of NSVT on Holter is an independent
predictor of all-cause mortality in patients with CCCD.408,436
In the RASSI score, the identification of NSVT on Holter adds
3 points of a total of 18 or 20 possible points (women and
men, respectively). In addition to risk stratification, Holter
enables the assessment of symptoms, such as palpitations and
syncope, frequent in those patients and usually resulting from
the arrhythmias found.

Holter also enables the autonomic nervous system
assessment by use of heart rate variability (HRV) analysis.
Several studies have shown autonomic alterations in different
stages and forms of CD.⁴³⁷,⁴³⁸ Although parasympathetic
dysfunction predominates, sympathetic involvement (lower
intensity) is also present.²⁰⁴ A retrospective study has reported
preliminary evidence that such alterations, reflected in several
HRV parameters, can signal the risk for sudden death.⁴³⁹
The HRV assessed during short Holter recordings and with
machine learning technique has shown the ability to predict
echocardiographic alterations⁴⁴⁰ and could be correlated with
the RASSI score, the most endorsed prognosticator of mortality
risk, in patients with cardiomyopathy with or without associated
digestive involvement.⁴⁴¹

6.2.8. Intracardiac Electrophysiological Study

In CCCD, there are reentry arrhythmogenic substrates
related to areas of fibrosis, and the EPS enables the induction
of SVT or even VF, which, in some contexts, gain a prognostic
conotation.⁴⁴² In addition, the EPS allows the sinus node and
atrioventricular conduction assessment, as well as defining
accurately whether the dromotropic disorder is in the
atrioventricular node or His bundle, or is infra-Hisian. The
frequent paroxysmal occurrence of TAVB due to the His-
Purkinje system impairment, consequent to its well-known
conduction behavior in the “everything or nothing” form
(either conducts or not, without intermediate stages of poor
function), determines that, in certain cases, only the invasive
investigation with EPS allows the accurate diagnosis and
proper treatment.⁴⁴²

6.2.9. Exercise and Cardiopulmonary Tests

The conventional maximum exercise test and the
cardiopulmonary assessment test can detect important
alterations, such as ventricular arrhythmias induced by exercise
and chronotropic incompetence.⁴⁰⁵,⁴⁴³ However, the general
clinical applicability of the exercise test has not been well
established, although the cardiopulmonary test, with direct
measurement of oxygen consumption (VO₂max), can be
considered gold-standard for assessing physical functioning
and efficacy of rehabilitation programs.⁴⁴⁴

Exertion-induced ventricular arrhythmias are a marker
of cardiovascular death risk in patients with CD.⁴⁴³ Because
these arrhythmias also occur in patients with no apparent cardiopathy, conventional maximum exercise test is clinically relevant for risk stratification in the population with CD, especially regarding work legal advice.

Few studies have assessed the efficacy of exercise test variables in predicting the survival of patients with CCCD. The VO₂peak is an important criterion for CTX in patients with advanced forms of cardiopathy. However, its prognostic value should be better understood in the context of preventive strategies, risk stratification, and early diagnosis. In addition, cutoff points should be established to be specifically used in CCCD.

## 6.2.10. Cardiac Catheterization

As already mentioned, patients with CCCD frequently have atypical chest pain and electrocardiographic abnormalities, such as ST-segment changes and pathological Q waves, in addition to regional contractile and myocardial perfusion disorders that mimic coronary atherosclerotic disease. In most cases, assessment of epicardial coronary arteries shows no obstructive subepicardial atherosclerotic disease, those changes being attributed to coronary microvascular dysfunction.³³⁶,⁴⁴⁵

Recent studies have evidenced that the ventricular dysfunction associated with CD microvascular disease is more prominent than that observed in the microcirculatory disorder from other etiologies.⁴⁴⁶ In addition, researchers have reported improvement in symptoms and myocardial perfusion when patients with CCCD were treated with platelet inhibitors and microvascular vasodilators, the first demonstration of benefit achieved in this context.⁴⁴⁷

Cardiac catheterization, thus, can be used when patients with intermediate or high probability of obstructive coronary artery disease have typical anginal pain and/or multiple risk factors for atherosclerotic disease or a large ischemic area evidenced on noninvasive tests. During the hemodynamic study, contrast left ventriculography, because of its high temporal and spatial resolution, can show small apical aneurysms and/or other segmental ventricular contractile changes, which might not be detected on other imaging methods.³³⁶ In addition, cardiac catheterization can be performed in candidates to CTX due to advanced HF to assess pulmonary vascular resistance. Moreover, cardiac catheterization enables performing post-transplant endomyocardial biopsy when the differentiation between rejection and *T. cruzi*-infection reactivation is mandatory in some patients.

## 7. Risk Stratification and Prognosis

Chronic cardiomyopathy of Chagas disease can manifest in several forms, depending basically on the severity of the myocardial and electrical conduction system alterations, presence and type of arrhythmias, and existence of HF. Two systematic reviews with meta-analyses have been recently published. One of them has assessed the risk of progressing to chronic cardiomyopathy in individuals in the acute phase (global estimated occurrence of 4.6% [95% CI, 2.7%-7.9%] annually) or

in those with the IFCD (annual estimate of 1.9% [95% CI, 1.3%-3.0%]).²⁹⁷ The other systematic review with 52 studies including only patients with manifest cardiopathy has shown an annual mean rate of mortality of 7.9% [95% CI, 6.3%-10.1%], but with highly heterogeneous results, and individual rates ranging from 0.5% to 38.3%/year, depending on the baseline characteristics of each study population⁴⁴⁸ (Figure 7.1).

In recent decades, several risk factors for morbidity and mortality have been identified to quantify the severity of CCCD, assess its prognosis, and suggest more suitable therapeutic strategies. However, when considered in isolation, variables associated with worse prognosis usually have low positive predictive value, which limits their use. Thus, prognostic models built from several combinations of demographic, clinical, and laboratory parameters began to be investigated.

To be applied in clinical practice, the risk stratification model should be simple and use a non-excessive number of variables that are well defined, easily accessed, and have satisfactory discriminatory power (C statistics). Even more important, the model should be validated by researchers from other centers (geographical validation) and in posterior periods (temporal validation), and, if possible, be capable of predicting other outcomes different from that to which it was developed and in different scenarios (wide or expanded validation).⁴⁴⁹

It is worth emphasizing that prognostic models without external validation, even if properly developed, are of little use and have low evidence-based sustainability, being not recommended for daily practice use. Usually, the prognostic model performs better in the data set from which it originated than in the new data set in validation analyses.⁴⁴⁹

In 2006, Rassi Jr et al.⁴⁰⁸ developed and validated a risk score to predict all-cause death in CCCD. In an original cohort involving 424 outpatients with a mean 7.9-year follow-up, total mortality was 31% (130/424), deaths due to cardiovascular causes represented 87% of the total (113/130), and sudden cardiac death represented 62% of the total (81/130). In the external validation cohort (153 patients), the total mortality rate was 23% (35/153) in a mean 7.7-year follow-up, and most deaths (57%) occurred suddenly.

Multivariate analysis identified six independent predictors of mortality, which were attributed points corresponding to their strength of association with the outcome in question (total mortality) based on the Cox model beta regression coefficient (Figure 7.2A). The individuals were classified into subgroups of low, intermediate, and high risk, based on the total sum of each patient's points. Total mortality in 10 years and the survival curves of those three subgroups are shown in Figure 7.2B and 7.2C. The C statistics for the system of points was 0.84 in the development cohort and 0.81 in the validation cohort. Except for male sex for cardiovascular death and low QRS voltage for sudden death, which showed borderline statistical significance, the other variables were also strong predictors of risk for those two specific types of death.⁴⁰⁸

In addition to showing unequivocal discriminatory power, the RASSI score has the following advantages: uses only six easily-measurable or collectable variables, extracted from usually available tests (ECG, chest X-ray, two-dimensional ECHO, and 24-hour Holter), which are part of the initial
<figure><img src="image_6.png" /><figcaption>**Figure 7.1** – Annual progression rate of Chagas disease (diagnosed acute phase and chronic indeterminate form) to cardiomyopathy and from chronic cardiac form to death.</figcaption></figure>

<figure><img src="image_7.png" /><figcaption>**Figure 7.2** – RASSI score. (A) Risk markers and respective points; (B) Total mortality in 10 years in the low-, intermediate-, and high-risk subgroups; (C) Kaplan-Meier actuarial curves. pts: points, NSVT: Nonsustained ventricular tachycardia.</figcaption></figure>

mandatory investigation of patients with CCCD; assesses LV function subjectively, dismissing ejection fraction measurement by the Simpson method and valuing both global and segmental myocardial contractility changes, which have recently been confirmed as important independent predictors of risk for cardiovascular events by use of careful analysis of the BENEFIT

study database;³⁴² enables replacing the CTI measurement on chest X-ray by LVDD measurement on ECHO, because a good correlation between CTI > 0.50 and LVDD > 60mm has been observed;³³⁷ requires the use of neither formulas nor calculators because it is a feasible score of simple memorization; can predict the three major causes of death: total, cardiovascular, and
# Guidelines

sudden;⁴⁰⁸ and was externally validated in four different cohorts, at different times, and by independent researchers.⁴⁰⁸,⁴²⁴,⁴⁵⁰,⁴⁵¹ Of note in two of those cohorts,⁴²⁴,⁴⁵¹ the outcome assessed was different from that of the original publication (total death), and, even so, the RASSI score showed highly reproducible results (Table 7.1).

The RASSI score strength, particularly regarding its accuracy for stratification in subgroups of risk, is supported by results of recent investigations in different contexts, showing, for example, a strong positive correlation of the risk levels with the following: cardiac dysautonomia grade;⁴⁴¹,⁴⁵² myocardial fibrosis presence and extension on CMRI detected with late enhancement technique⁴²⁴,⁴²⁸,⁴⁵³ or T1 mapping,⁴²⁵ the latter assessing the interstitial component of myocardial fibrosis; and the induction of sustained ventricular tachyarrhythmias on EPS.⁴⁵⁴

In another study, assessing patients who had undergone cardiopulmonary exercise testing, the RASSI score addition to the anaerobic threshold increased the area under the ROC curve from 0.706 to 0.800, and all-cause death was the primary outcome on logistic regression analysis.⁴⁵⁵

When assessing the prevalence and prognostic value of ventricular dyssynchrony on ECHO and of the RASSI score in patients with CCCD, considering as outcome the combination

of total death and hospitalization, only the RASSI score could predict the combined events on multivariate analysis (OR = 1.19; 95% CI, 1.02-1.40; p = 0.01).⁴⁵⁶

In patients with HF and LVEF< 45%, when assessing the prognostic value of the variables obtained on cardiopulmonary exercise testing and of other variables, only the increased VE/VCO₂ slope (HR = 2.80; 95% CI, 1.30-5.80; p = 0.001, cutoff point of 32.5) and the RASSI score (HR = 1.28; 95% CI, 1.10-1.48; p = 0.001) associated with higher mortality on multivariate analysis after a mean 32-month follow-up.⁴⁵⁷

A systematic review of 12 studies (1985 to 2006),⁴⁵⁸ using multivariate analysis to better assess prognosis in CCCD and comprising approximately 4300 patients, has shown that the most consistent and relevant predictors of total mortality, sudden cardiac death, and cardiovascular death were New York Heart Association (NYHA) functional class III or IV, cardiomegaly on chest X-ray, LV systolic dysfunction assessed on ECHO or cineventriculography, in addition to NSVT on 24-hour Holter. Using these four variables in an integrated way, an algorithm can be elaborated to stratify the risk of death in patients with CD in a simplified and logic way by use of clinical parameters and complementary methods available in most cardiologic services in our country (Figure 7.3).

<table><caption>**Table 7.1 – RASSI score: results of the original cohort (Hospital São Salvador, Goiânia) and external validation in four different cohorts.**</caption><thead><tr><th rowspan="2">Author</th><th rowspan="2">Study period</th><th rowspan="2">Study site</th><th rowspan="2">N of patients</th><th rowspan="2">Outcome</th><th colspan="3">% Outcome (5 years)</th><th colspan="3">% Outcome (10 years)</th><th rowspan="2">C Statistics</th></tr><tr><th>low risk (0-6 pts)</th><th>intermediate risk (7-11 pts)</th><th>high risk (12-20 pts)</th><th>low risk (0-6 pts)</th><th>intermediate risk (7-11 pts)</th><th>high risk (12-20 pts)</th></tr></thead><tbody><tr><td>Rassi A Jr. et al.³</td><td>1986-1991</td><td>Hospital São Salvador (Goiânia)</td><td>331*</td><td>Total death</td><td>2 (0-5)</td><td>18 (8-28)</td><td>63 (51-75)</td><td>10 (5-14)</td><td>44 (31-57)</td><td>84 (74-93)</td><td>0.84 (0.79-0.89)†</td></tr><tr><td>Rassi A Jr. et al.³</td><td>1990-2001</td><td>Hospital Evandro Chagas (RJ)</td><td>153</td><td>Total death</td><td>0</td><td>15 (1-28)</td><td>53 (31-75)</td><td>9 (2-16)</td><td>37 (16-59)</td><td>85 (63-100)</td><td>0.81 (0.72-0.90)†</td></tr><tr><td>Rocha MOC & Ribeiro AL⁶</td><td>1998-2006</td><td>Universidade Federal de Minas Gerais</td><td>158</td><td>Total death</td><td>3 (1-7)</td><td>10 (4-22)</td><td>67 (30-90)</td><td>NA</td><td>NA</td><td>NA</td><td>0.84 (0.72-0.96)</td></tr><tr><td rowspan="2">Benchimol Barbosa PR et al.⁷</td><td rowspan="2">1995-2003</td><td rowspan="2">Hospital Universitário Pedro Ernesto (RJ)</td><td rowspan="2">100</td><td>Cardiac death or VT§/†</td><td>4 (1-11)†</td><td>42 (18-83)†</td><td>50 (6-100)†</td><td>28 (18-43)</td><td>58 (29-100)</td><td>75 (15-100)</td><td>0.79 (0.70-0.88)†</td></tr><tr><td>Cardiac death#</td><td>NA</td><td>NA</td><td>NA</td><td>NA</td><td>NA</td><td>NA</td><td>0.81 (0.69-0.93)†</td></tr><tr><td rowspan="2">Senra T et al.⁸</td><td rowspan="2">2001-2011</td><td rowspan="2">Instituto do Coração - INCOR (SP)</td><td rowspan="2">130</td><td>Total death, cardiac transplantation, ICD appropriate therapy or resuscitated CA#</td><td>16</td><td>42</td><td>76</td><td>NA</td><td>NA</td><td>NA</td><td>NA</td></tr><tr><td>Total death#</td><td>11</td><td>33</td><td>57.5</td><td>NA</td><td>NA</td><td>NA</td><td>NA</td></tr></tbody></table>

The numbers between parentheses correspond to the 95% confidence interval. * multivariate model applied to 331 patients from the original cohort of 424 patients (those with missing data were excluded); †relative to 10 years; §defined as 3 or more successive beats; †primary outcome; ‡outcome by 50 months; #secondary outcome; ICD: implantable cardioverter-defibrillator; N: number; NA: not available; CA: cardiac arrest; VT: ventricular tachycardia.
<figure><img src="image_8.png" /><figcaption>**Figure 7.3** – Risk stratification algorithm in Chagas disease. NSVT: nonsustained ventricular tachycardia; LV: left ventricular. \*can be replaced by LV diastolic diameter > 60 mm on echocardiogram; †global or segmental. Adapted from Rassi A Jr, Rassi A, Rassi SG. Predictors of mortality in chronic Chagas disease. Circulation. 2007;115:1101-8.⁴⁵⁸</figcaption></figure>

The presence of NYHA functional class III or IV, per se, identifies high-risk cases, because almost all these patients have systolic ventricular dysfunction on ECHO and NSVT on Holter. Of note, the combination of ventricular dysfunction with NSVT, independently of the functional class, identifies a group with a 15-fold higher risk as compared to patients without both abnormalities.⁴⁵⁸

Although the RASSI score has a well-established theoretical base as an independent predictor of fatal events and has been externally validated in multiple studies, it is infrequently used on the daily practice. One of the reasons for that might be the low availability in the Brazilian SUS, outside university-affiliated hospitals, of the simple diagnostic methods used for calculating the score, such as ECHO and 24-hour Holter. This guideline, by strongly recommending the application of the RASSI score as the principal method for risk stratification of all patients as soon as the diagnosis of cardiomyopathy is confirmed, as already established in other consensus of international societies,⁴⁵⁹ expects to solve that deficiency.

In addition, despite projecting the risk of death in the long run and under highly heterogeneous prognostic conditions, the RASSI score usefulness to guide clinical management and subsequent therapy is yet to be determined. It is worth noting

that the valuable information on risk provided by the score to patients and their physicians can guide follow-up and, possibly, treatment strategies. In this way, the Brazilian multicenter RCT CHAGASICS (CHronic use of Amiodarone aGAINsT Implantable Cardioverter-defibrillator) is in its conclusion phase. It compares amiodarone versus defibrillator for total mortality reduction as a primary prevention strategy and has the following inclusion criteria: presence of at least one NSVT episode on 24-hour Holter and a RASSI score ≥ 10 points.⁴⁶⁰

Furthermore, it is plausible to speculate that low-risk patients (10-year mortality of 10%, similarly to that of the low-risk group according to the Framingham score) can undergo annual clinical reviews, while intermediate- or high-risk patients should do it more often (every 3 or 6 months).

Other studies on the CCCD prognosis have focused on different risk markers, such as: LVEF reduction;⁴⁶¹⁻⁴⁶³ RV systolic dysfunction (Tei index);³⁵⁰ LV diastolic dysfunction (E/e' ratio);⁴¹⁶ left atrial volume increase;⁴¹⁵ changes in myocardial deformation indices;⁴¹²,⁴⁶⁴ parasympathetic and sympathetic dysfunction;²⁰⁷,⁴⁶⁵ specific changes on ECG;³⁰³ T-wave amplitude variability;⁴⁶⁶ T-wave axis deviation;⁴⁶⁷ QT interval dispersion;⁴⁶³,⁴⁶⁸ changes on high-resolution ECG (spectral turbulence and filtered QRS);⁴³⁶,⁴⁵¹ HRV reduction;⁴⁵¹ prolonged
# Guidelines

QRS complex duration;⁴⁶⁹ VO₂ peak reduction;⁴⁶¹ exercise time reduction;⁴⁷⁰ increased serum levels of type B natriuretic peptides (BNP and NT-proBNP);⁴⁶⁹,⁴⁷¹ and others.⁴⁷² Such factors and variables, when analyzed by use of multivariate models or transformed into risk scores, associate with worse prognosis. In addition, they provide information on the mechanisms related to disease progression and the less explored aspects of their complex prognostication.

However, as the above mentioned studies are very heterogeneous, acknowledging their limitations is necessary.⁴⁷³,⁴⁷⁴ The following limitations affect their applicability: use of non-standardized variables that are difficult to measure and to reproduce, usually extracted from complementary tests of restrict access or not available in common practice; inclusion of a reduced number of patients or outcomes; non-inclusion of all variables known to be associated with worse prognosis in most of those models (the four previously cited); and, particularly, absence of external validation.⁴⁷³

Thus, the scores proposed are not ready to be used in routine medical care, because almost all studies lack external and independent validation.⁴⁷³,⁴⁷⁴ It seems there is a growing number of publications trying to develop new risk models rather than validating or improving the existing ones.⁴⁷⁴

A recent study, using data from the NIH SaMi-Trop cohort,⁴⁷⁵ has developed a simplified score to be used in endemic regions without access to cardiological investigation other than ECG. The score included clinical and electrocardiographic data, in addition to NT-proBNP measurement, to predict the risk of death in 2 years of patients with CCCD.⁴⁶⁹ Five independent predictors of death were identified and points were attributed as follows: age (10 points per decade); NYHA functional class greater than I (15 points); HR ≥80 beats/min (20 points); QRS duration ≥ 150ms (15 points); and abnormal age-adjusted NT-proBNP (55 points). Patients were then classified into three risk categories (low, < 50 points; intermediate, between 50 and 100 points; and high, > 100 points). External validation was performed applying the score to another independent population with CD. After a 2-year follow-up, in the development cohort, 110 patients died, and the global mortality rate was 3.5 deaths per 100 individuals-year. The mortality rates observed in the groups of low, intermediate, and high risk were 0%, 3.6%, and 32.7%, respectively, in the derivation cohort, and 3.2%, 8.7%, and 19.1%, respectively, in the validation cohort. The score discrimination was good in the development cohort (C statistics: 0.82) and the validation cohort (C statistics: 0.71).⁴⁶⁹ The major limitations of the score are the use of NT-proBNP measurement, which is not usually available in PHC, and lack of independent and extensive external validation, as occurs with the RASSI score.

In two other studies, the mere identification⁴²⁸ or quantification⁴²⁴ of myocardial fibrosis with the late enhancement technique in CMRI, as a continuous variable (expressed in unitary value of additional gram) or as dichotomous variable (using the cutoff point of 12.3 g), proved to be an important risk predictor for severe cardiovascular events, such as total death, cardiovascular death, and occurrence of sustained ventricular tachyarrhythmias, independently of the ventricular function and RASSI score. It is worth noting that one of the studies⁴²⁴ enabled the direct

comparison between the prognostic value of the myocardial fibrosis amount and the RASSI score.

Using total mortality as the final outcome (considered secondary outcome), after a median 5.4-year follow-up, the power of association of the RASSI score was more significant than that of myocardial fibrosis. Expressed as categorical variables (low, intermediate, and high risk for the RASSI score and mass < 12.3 and ≥ 12.3g for myocardial fibrosis), only the RASSI score was associated with worse prognosis (HR: 1.24; 95% CI, 1.13-1.36; p < 0.001 versus HR: 1.33; 95% CI, 0.68-2.61; p = 0.406). Expressed as continuous variables (RASSI score in points and myocardial fibrosis in grams), both were risk predictors, but with higher relevance for the RASSI score (HR: 1.23; 95% CI, 1.12-1.35; p < 0.001 versus HR: 1.02; 95% CI, 1.00-1.04; p = 0.043), that is, for each additional point in the RASSI score, the risk of death increases by 23%, while for each 1 additional gram of myocardial fibrosis, that increase is of only 2%. The mass of fibrosis, as dichotomous variable, had a C statistic of 0.709 (95% CI, 0.618-0.793) to predict death from any cause, while, for the RASSI score, that value was not informed.⁴⁷⁶

Another relevant result of that study was the ability of the RASSI score and myocardial fibrosis to predict the combined outcome of death from any cause, CTX, resuscitated sudden death, appropriate shock or ICD antitachycardia therapy, a less important outcome from the risk hierarchical viewpoint, but considered the primary outcome in the study in question. Despite these expressive results with the RASSI score,⁴⁷⁷ the authors concluded only that myocardial fibrosis could contribute to improve risk stratification and might guide the treatment of patients with CCCD.⁴²⁴

In the assessment of CCCD, CMRI is not one of the initial diagnostic tests and might not be included in the routine cardiological assessment because of its high cost, unavailability in several centers, and some relative or absolute contraindications to its performance (for example, claustrophobic patients, individuals with orthoses/prostheses, older PM models, or renal failure when gadolinium injection is required). Also, the method should still be tested to assess if it can improve the performance of the already existing risk stratification models by use of new statistical techniques, such as reclassification table, net reclassification index (NRI) and integrated discrimination index (IDI).⁴⁷⁸

According to the prevalence of the risk groups in the RASSI score, it is known that if it is applied to 1000 patients with cardiomyopathy, 610 will be classified as at low risk for total death, 190 as at intermediate risk, and 200 as at high risk. With death rates in 10 years of 10%, 44%, and 84%, respectively, for the three subgroups,⁴⁰⁸ by the end of 10 years we would have 61 deaths in the low-risk group, 84 deaths in the intermediate-risk group, and 168 deaths in the high-risk group. Thus, of a total of 313 deaths in the 10-year follow-up, although most deaths (168 or 54%) occur in the high-risk group (which is desirable in terms of risk stratification), we would still have 145 deaths in the low- and intermediate-risk groups. For a new risk predictor to prove its clinical usefulness, once added to the RASSI score, it should ideally be able to correctly identify the low- and intermediate-risk patients who will die or, less likely, those at high risk who will survive. Myocardial fibrosis might be that marker, a hypothesis yet to be tested.
In addition, there is no report in the literature that a change in the RASSI score (particularly a reduction in the number of points) can assess and monitor the efficacy of a certain treatment and improve patients' prognosis. However, because the score includes six variables, attributing 0 to 20 points to the set, and two variables are more likely to undergo changes (NYHA functional class III/IV and presence of NSVT on Holter), this is another interesting investigation to be considered.

Finally, it is worth emphasizing that patients aged > 70 years, or with artificial cardiac PM, or documented SVT or VF, by being a priori at high risk for death, as well as patients with ischemic, hypertensive or associated valvular disease, to prevent confusion with deaths not related to CCCD, were excluded from the calculation and standardization of the RASSI score.408

The prognostic value of the EPS in patients with CCCD is yet to be established. Regarding primary prevention of sudden death, data available suggest that the EPS has no prognostic usefulness in patients with isolated VE or NSVT, provided the LV systolic function is normal. In a study including 72 patients with preserved LV function (mean ejection fraction of 0.60) and 400 to 1200 VE/hour on Holter (35% with NSVT), the programmed ventricular stimulation did not induce SVT in any patient.479 In the mean 36-month follow-up, only 1 of the 72 patients presented spontaneous SVT.

Another study408 has assessed the prognostic value of SVT induction in response to programmed ventricular stimulation in 78 patients with NSVT on Holter (mean LVEF of 0.47 ± 0.18) and no clinical history of sustained arrhythmias. Monomorphic SVT was induced in 25 patients (32%), all of them treated with class III antiarrhythmic drugs, most of them with amiodarone and only one with sotalol. After mean 56-month follow-up, the probabilities of cardiac death and combined events (cardiac death, spontaneous SVT, or syncope recurrence) were 2.2 and 2.6 times greater (p < 0.05), respectively, in inducible patients as compared to non-inducible. In contrast, the induction of polymorphic VT or VF had no prognostic significance, being, probably, an unspecific ventricular response to the test.480

Regarding secondary prevention (patients with documented sustained ventricular arrhythmias or resuscitated sudden death), some authors have assessed the importance of EPS for risk stratification and antiarrhythmic therapy choice, but data available are limited.

The largest observational study481 has included 115 patients with symptomatic VT (mean LVEF of 0.49 ± 0.14), of whom, 78 with spontaneous SVT and 37 with spontaneous NSVT and EPS-induced SVT. After impregnation with Vaughan-Williams class III antiarrhythmic drugs (sotalol or amiodarone), the patients were divided into three groups, based on their responses to a subsequent electrophysiological test. Patients in group 1 had no inducible SVT, those in group 2 had well-tolerated inducible SVT, and those in group 3 had hemodynamically unstable inducible SVT. After a mean 52-month follow-up, the total mortality rate was significantly higher in group 3 as compared to groups 1 and 2 (69% versus 26% and 22%, respectively).481

Based on those results, although the EPS can identify patients at higher risk for death or who do not respond well to treatment with antiarrhythmic drugs, its role in guiding other types of therapies, such as ICD implantation, remains undefined, resulting in little usefulness of the method for that purpose.

## 8. Therapeutic Management in the Indeterminate Form of Chagas Disease

The IFCD is a latent period that usually begins right after the end of the acute phase and can last indefinitely, for an individual's entire life. This stage of CD has been recognized since the first studies by Carlos Chagas²²⁹,³⁰⁴,⁴⁸² and was classically confirmed in 1985,³⁰¹ when it was defined as the situation of an asymptomatic chronically *T. cruzi*-infected individual, with normal physical examination and no changes on chest X-ray, conventional ECG, and esophageal and colonic contrast radiography.

The classical definition of the IFCD does not include individuals with “unspecific” electrocardiographic changes, which do not define CCCD.⁴⁸³,⁴⁸⁴ In this situation, the term “without apparent cardiopathy” should be used instead. Similarly, that classical denomination does not apply to patients without digestive symptoms, who had undergone neither esophageal nor colonic assessment by use of contrast imaging tests.

Chart 8.1 shows changes that usually define the presence of CCCD and those that alone are not sufficient to make that diagnosis, being considered “non-defining”. These “unspecific” changes should be cautiously interpreted, taking into consideration the underlying clinical context.³²⁸,⁴⁸⁵ For example, low QRS complex voltage in the frontal plane, which indicates poor prognosis according to the RASSI score, can also be detected in individuals with emphysema or morbid obesity (Chart 8.1).

In addition, it is worth noting that a normal ECG finding, despite being a defining criterion of IFCD, is not a reliable absolute indicator of absence of cardiac impairment. When deepening the investigation by using other diagnostic methods, such as ECHO,³¹²,³¹³,⁴⁸⁶⁻⁴⁸⁹ exercise or cardiopulmonary test,⁴⁹⁰,⁴⁹¹ 24-hour Holter,⁴¹³,⁴⁹²⁻⁴⁹⁶ noninvasive autonomic function tests,²³⁶,⁴⁰⁵,⁴³⁸,⁴⁹⁷⁻⁴⁹⁹ cardiac scintigraphy,¹⁸³,³⁴⁵,⁵⁰⁰,⁵⁰¹ hemodynamic and coronary angiographic studies,⁵⁰² CMRI,³¹¹,⁴⁵³,⁵⁰³,⁵⁰⁴ and even endomyocardial biopsy,⁵⁰⁵ a substantial number of patients with normal ECG shows abnormalities in some of those tests that are usually mild or of low intensity or of isolated frequency.

Most of those test abnormalities with little if any clinical repercussion can be occasionally found in healthy individuals not infected with *T. cruzi*.⁵⁰⁶⁻⁵⁰⁸ Thus, although some studies have evidenced those changes in some individuals, the concept of IFCD remains valid,²⁹⁹ being practical and widely applicable.³⁰⁰ The proposal for modifying the criteria – including replacing chest X-ray with transthoracic ECHO at rest – did not move forward.³⁰⁶

However, although some studies have shown that those alterations do not impact progression to CCCD,²¹¹,⁵⁰⁹ thus
# Guidelines

<table><caption>Chart 8.1 – Electrocardiographic changes of Chagas disease</caption><thead><tr><td>Defining of CCCD</td><td>Non-defining (unspecific)*</td></tr></thead><tbody><tr><td>Sinus bradycardia ≤ 40 bpm</td><td>Sinus bradycardia > 40 bpm</td></tr><tr><td>Polymorphic ventricular extrasystole</td><td>Isolated ventricular extrasystole</td></tr><tr><td>Complete right bundle branch block</td><td>Incomplete right bundle branch block</td></tr><tr><td>Primary ventricular repolarization abnormalities</td><td>Secondary ventricular repolarization abnormalities</td></tr><tr><td>2<sup>nd</sup> and 3<sup>rd</sup> degree atrioventricular block</td><td>1<sup>st</sup> degree atrioventricular block</td></tr><tr><td>Complete left bundle branch block</td><td>1<sup>st</sup> degree left bundle branch block</td></tr><tr><td>Electrically inactive area</td><td>Mean QRS electrical axis deviation to the left</td></tr><tr><td>Sinus node dysfunction</td><td>Sinus arrhythmia (non-respiratory)</td></tr><tr><td>Nonsustained and sustained ventricular tachycardia</td><td>Sinus tachycardia</td></tr><tr><td>Atrial fibrillation</td><td>Left anterior fascicular block</td></tr><tr><td>Atrial flutter</td><td>Low-voltage QRS</td></tr><tr><td>Ventricular fibrillation</td><td>Wandering atrial pacemaker</td></tr></tbody></table>

supporting the notion that they lack prognostic connotation, most studies' results require better assessment in a longer follow-up. So far, there is no definitive proof that those changes do not act as potential triggers for future cardiovascular events.

Despite decades of research, the factors that lead to the development of CCCD in 30% of the individuals with the IFCD have not been totally clarified.¹⁷⁶ Several factors are involved in the risk for IFCD progression to CCCD, such as: age; male sex; geographical origin; parasite load intensity; *T. cruzi* strain and its discrete typing units (Tcl–TcVI and Tc-bat); host’s genetic aspects; severity of the initial acute infection related to the transmission mode; exposure to reinfection with the parasite in sustained vectorial transmission areas; host’s nutritional status and presence of comorbidities; social context; quality of life of individuals with CD; and absence of trypanocidal treatment.²⁴⁷,²⁹⁷,⁵¹⁰-⁵¹⁷

Although knowledge on the natural history of CD is scarce, it is worth emphasizing the usually good prognosis of IFCD,⁵⁰⁹,⁵¹⁸,⁵¹⁹ with mortality overlapping that of the non-infected general population, as long as the ECG findings are normal.⁴⁰⁴ An individual with IFCD can remain for several decades in that condition,²⁹⁹,³⁰⁰ and annual or even biannual serial ECG can detect progression to CCCD.²

Electrocardiographic changes can appear during follow-up in varying percentages, but with no direct relation to LVEF, which usually remains unaltered.²¹¹ The annual rates of progression from IFCD to CCCD vary from 0.3% to 10.3% (mean of 1.9%).²⁹⁷ In IFCD, the presence of changes on ECHO due to regional dyssynergies, even when the global systolic ventricular function is preserved, can imply a risk for clinical events, such as TAVB, stroke, ventricular tachyarrhythmias and/or HF, indicating worse prognosis as compared to that of individuals in the IFCD with normal ECHO findings.³⁴¹,⁴¹⁸

The good prognosis of patients with the IFCD has been reported in several longitudinal studies that concluded that individuals with the IFCD and controls not infected by *T. cruzi* in the same age group have similar mortality rates.²⁹⁹,⁴⁰⁴,⁵¹⁹ The annual incidence of sudden death among individuals with CD and normal ECG is low and similar to that of the population without CD.⁵²⁰ Sudden death is a rare complication that occurs in the general population equally; thus, its cause should not straightaway be attributed to CD.

Regarding treatment with trypanocidal drugs in the chronic phase of CD, the IFCD is one of the major indications,⁸,⁶⁰ and young adults treated with those drugs less often progress to CCCD as compared to non-treated ones.³²⁰-³²³,⁵²¹

The follow-up of individuals with the IFCD should be maintained at the PHC level, with annual or biannual electrocardiographic assessment, because some electrocardiographic changes have an evolutive character and define the CCCD.⁵²² A patient with normal ECG and segmental ventricular contractile abnormalities on ECHO should undergo the same investigative assessment given to a patient with an electrocardiographic abnormality that defines CCCD.

Patients with the IFCD can have comorbidities whose frequency increases as the population ages.⁵²³ In patients with IFCD, the relation between aging and comorbidities seems not to depend on the presence of CD itself.⁵²⁴ However, old patients with IFCD constitute a particularly vulnerable population group regarding the harmful effects of chronic degenerative diseases.⁵²⁵ Among cardiovascular comorbidities, systemic arterial hypertension (SAH) predominates, followed by coronary artery disease.⁵²⁶ The monitoring and treatment of these comorbidities, in addition to dyslipidemia and diabetes mellitus, should be

<footnote>*The 'unspecific' changes, when isolated, are usually considered insufficient to make the diagnosis of chronic cardiomyopathy of Chagas disease (CCCD). When combined, however, they make that diagnosis more likely. For example, ventricular extrasystole in association with low-voltage QRS and intraventricular conduction disorders (even without complete block) should suggest the diagnosis of CCCD. Individual situations of uncertainty in grey zones of ECG changes may exist and should be judiciously clarified by the physician. Adapted from Biolo et al.⁴⁸⁵</footnote>
individualized. Controlling these conditions is fundamental
to the secondary prevention of CCCD.<sup>527,528</sup>

The general medical management of an individual
chronically infected by *T. cruzi* (confirmed by at least
two positive serological tests with different laboratory
techniques) should be conservative aiming to characterize
IFCD and establish the following recommendations: 1)
In the absence of cardiovascular and digestive symptoms
(particularly, dysphagia and constipation) with normal
findings on physical examination and ECG (preferably with
30-sec recording acquired on a single lead), no additional
test is necessary, not even chest, esophageal, and colonic
radiography; 2) Directed anamnesis, physical examination,
and ECG should be repeated annually or biannually;
3) Physical exercises should not be restricted, not even
competitive ones; 4) No professional restriction applies,
not even for the conduction of collective vehicles; and 5)
Psychological support is essential, explaining the favorable
prognostic notions, which guide the most conservative
medical managements.

In patients with IFCD, performing ECG annually or biannually is strongly recommended, with level of evidence B. It is worth emphasizing that trypanocidal treatment with benznidazole should be offered to individuals with the IFCD up to the age of 50 years, as a strong recommendation, level of evidence B.

9. Etiological Treatment of Chagas Disease

9.1. Introduction

Ensuring effective, efficient, and safe access to etiological
treatment (trypanocidal) for *T. cruzi* infection remains a
critical challenge when analyzing the advances over the past
50 years.<sup>2,3,38,44,56,58,112,113,529</sup> The importance of that type of
treatment for CD is unequivocal for individuals affected and
for their families and communities. This is a central issue for the
national health systems, and barriers should be overcome to
ensure access to diagnosis and proper treatment to all patients.<sup>2,5</sup>
This ethical dilemma requires a more proactive behavior of
healthcare managers and professionals (particularly physicians,
including cardiologists), social movements, and all stakeholders.

Chagas disease belongs in the large group of NTD, and
critical flaws of science, market environment, and public health
make its management even more challenging.<sup>49,52,530</sup> Advances
in the field have been insufficient for a consistent public health
response aimed at controlling the disease in the local health care
network of several countries.<sup>44,54,94,531-533</sup> In many locoregional
scenarios, diagnostic methods and therapeutic drugs are not
available, and the local populations are not properly informed
about them.

For the past five decades, there has been a huge limitation
of etiological treatment options, with availability of only two
drugs that proved effective, benznidazole (1971) and nifurtimox
(1965).<sup>1,2,5,8,44,54,377,534-536</sup> There is strong evidence that both
drugs are effective in reducing disease's duration and clinical
severity by enabling the elimination of parasites with early

treatment,<sup>1,2,8,44,46,60,377,379</sup> with potential gains in quality of life
through prevention of physical functioning limitations.<sup>43,537</sup>

Benznidazole is still the most effective trypanocidal drug, which has been systematically confirmed in clinical trials comparing it with new drugs. However, there are critical gaps for the development of new less toxic therapeutic options aimed at improving the safety profile and access to treatment. The conduction of new studies is strategic to assess the use of not only combined therapies, but also shorter therapeutic schedules, with fixed and smaller doses. In addition, better and more reliable clinical parameters and laboratory biomarkers to assess treatment efficacy should be sought.<sup>536</sup> However, studies available so far have not allowed the recommendation of therapeutic schedules different from those classically established. It is worth noting that, in the Brazilian SUS, benznidazole is the most available and used drug, despite its limited operationalization relative to the expected demand.<sup>2,54,113</sup>

Proper etiological treatment is known to be cost-
effective<sup>5,50,52,53</sup> and has the potential benefit of reducing
parasitemia, with a positive impact on the patient's clinical
evolution, such as halting progression to the cardiac form,
reducing clinical complications in the two phases of disease,
increasing life expectancy, and improving physical functioning
and quality of life.<sup>2,8,32,41,43,53,318,322,323,537-540</sup>

One of the major challenges is the need to make etiological
treatment available and implemented in local health
systems<sup>2,8,112,113,533</sup> and to offer the drug continuously, which
is still hindered by the limited number of its providers and its
low demand in local health systems.<sup>56</sup> Thus, it is fundamental
to avoid missed opportunities to establish the diagnosis and
treatment. Considering that CD relates to poverty and social
vulnerability, the comprehensive healthcare of individuals with
CD will be able to reduce health inequities, particularly in
endemic territories,<sup>2,8,49,54,113</sup>

This specific chapter on etiological treatment is based on
the analysis of consensus, clinical protocols, and therapeutic
guidelines, which have been written and recently updated in
different contexts. They represent relevant strategies aimed
at contributing to increase access to diagnosis and treatment
to support clinical decisions.<sup>2,41,49,56</sup> The following referential
documents were based on the methodological procedures of
the GRADE system,<sup>27</sup> specifically adapted for these guidelines
(see chapter related).

One of the regional clinical guidelines analyzed is the 2019 PAHO/WHO Guidelines for the Diagnosis and Treatment of Chagas Disease (Guía para el diagnóstis y el tratamiento de la enfermedad de Chagas).<sup>60</sup> In addition, the 2011 I Latin-American Guideline for the Diagnosis and Treatment of Cardiopathy of Chagas Disease, coordinated by the SBC, was contemplated in the review.<sup>1</sup>

Considering that this is a national guideline and respecting
the specificities of the SUS pacts and organization, the major
reference for its elaboration was the Clinical Protocol and
Therapeutic Guidelines (PCDT) in CD, conducted by the
National Commission of Technology Incorporation in the SUS
(CONITEC), Secretariat of Science, Technology, and Strategic
Supplies of the Brazilian Ministry of Health.<sup>6</sup>
Additionally, the 2015 Second Brazilian Consensus on CD, an important landmark, coordinated by the Health Surveillance Secretariat of the Brazilian Ministry of Health in partnership with the Brazilian Society of Tropical Medicine,² was analyzed in the sequence of the 2005 Brazilian Consensus on CD.³

## 9.2. Drugs and Administration

Two antiparasite nitroheterocyclic compounds with efficacy established for the etiological treatment of CD are available: benznidazole, a nitroimidazole agent, and nifurtimox, a nitrofuran compound.⁵⁴,⁶⁰,³⁷⁷,⁵³⁴,⁵³⁵ Some clinical studies have included other drugs without proven efficacy, such as alopurinol and azole antifungal drugs (by molecule repositioning),⁸ which, however, are not included in the scope of this guideline.

Studies in the past 7 years have assessed the efficacy and safety of monotherapy or therapies combining benznidazole and other agents, such as posaconazole or fosravuconazole. Those studies were conducted in *T. cruzi*-infected individuals without evidence of damaged target organs, and their results were limited to only parasitological aspects with long-term qPCR assessment (12 months).³⁸⁵,⁵⁴¹,⁵⁴² Despite the disappointing results with the new drugs, the comparative studies reinforced the relevant role of benznidazole in the CD treatment.

A recent review has identified 109 epidemiological studies published after 1997 on the etiological treatment of CD (31 observational and 78 interventional), including 23 116 individuals. The studies were highly heterogeneous regarding not only clinical management for etiological treatment, but also study design and conduction, which limits the evidence available.⁵⁴³

The 'conditional' grade of recommendation established by PAHO for benznidazole and nifurtimox use, mainly in patients with chronic CD, is justified by the limited certainty level of the body of evidence on the results of efficacy, originating from the scarcity of RCT in this area.⁶⁰ In great part, evidence on CD should be presented because it is grounded on *T. cruzi* infection treatment. Once proved the trypanocidal action, in the absence of experimental randomized studies with relevant clinical outcomes, evidence from less robust, observational and good quality studies should be considered.

Moreover, considering the principle of asymmetry, the magnitude of an occasional damage from treatment, if it occurs, is significantly smaller than the benefit associated, particularly with qualified follow-up. Thus, the etiological treatment for CD is justified in a considerable number of cases.

From the perspective of the managers, treatment with benznidazole, thus, can be adopted as a health policy in specific contexts, considering the balance between benefits, risks, and health priorities. Healthcare professionals might have different choices for decision-making, which should always be shared with the individuals affected by the disease. Finally, most individuals affected, when well informed, most likely would want to receive the intervention.

Benznidazole is the first option in the Brazilian context, because of not only the larger experience with its use, but also its profile of adverse events and availability, particularly the

pediatric presentations.²,⁸,⁵⁴,¹¹³ The use of nifurtimox in Brazil is recommended when benznidazole is not tolerated, as in the occurrence of severe adverse events and in some other particular and specific circumstances.²,⁸,⁴⁶

The etiological treatment with any of these drugs should not be routinely and indiscriminately instituted for women of childbearing potential who are not on an effective contraceptive method.²,⁸,⁶⁰ Similarly, their indication in cases with other severe conditions (liver and kidney failure) should be carefully and individually assessed, according to clinical severity.

Benznidazole is available as tablets of 100mg and 50mg, for adults, and of 12.5 mg and 50 mg, for children. Its absorption occurs in the gastrointestinal tract, while its excretion is predominantly renal, with a mean life of 12 hours.¹ In the Brazilian SUS network, only tablets of 100 mg and 12.5 mg are available.⁵⁴,⁵⁴⁴ In 2017, benznidazole was approved by the USA Food and Drug Administration (FDA) for *T. cruzi* infection treatment, which, however, did not ensure full access to the drug in that country.⁵⁴⁵

The Brazilian Ministry of Health acquires the 100mg tablets of benznidazole and delivers them to the State Health Secretariats in response to requirements in the Strategic Supply Information System. The distribution flow to the regional health agencies and/or municipalities is established by each secretariat, integrating actions of pharmaceutical care, epidemiological surveillance, and primary healthcare.²,⁵⁴ However, the distribution of 12.5mg tablets of benznidazole is centralized in the Ministry of Health, because of the limited registry of pediatric cases in Brazil.²,⁵⁴

The process to define the proper dose of benznidazole that ensures efficacy and tolerability has been established through a trial-and-error approach.⁵⁴⁶ For adults with chronic CD, benznidazole is administered orally at the dosage of 5mg/kg/day divided into two or three doses, for 60 days, with a recommended maximum dosage of 300mg/day. For individuals with acute CD, the dose can be of as much as 10mg/kg/day. For individuals weighing over 60 kg, the therapeutic schedule can be extended to achieve the ideal target dose, maintaining 300 mg as the daily limit to prevent adverse events.²,⁸ The 300mg benznidazole regimen can be used for the number of days equivalent to the individual's weight, limited to a total of 80 days even for individuals weighing over 80 kg.¹,²,⁸ This dosage, which seems better tolerated, has been originally proposed by Professor Anis Rassi (*in memoriam*) and adopted later in the second half of the research with approximately 1500 individuals enrolled in the BENEFIT study, published in 2015.³²⁴

For children, the benznidazole dosage can vary from 5 to 10mg/kg/day, divided into two daily doses for 60 days, with a maximum dosage of 300mg/day. If the daily dosage exceeds 300 mg, extension of the treatment duration is recommended so the total calculated dosage for 60 days can be reached.¹,²,⁸ The pediatric formulation of 12.5mg soluble tablets can be used, enabling the treatment of newborns and children up to 2 years of age.²,⁵⁴ The major advantage of 50- mg tablets (not available in Brazil) is the possibility of treating the rest of the pediatric population, including adolescents and young adults.⁵⁴⁴
More recently, the randomized clinical trials CHAGASAZOL,³⁸⁵ STOP-CHAGAS⁵⁴² and E1224,⁵⁴¹ showing no long-term antiparasite effect of posaconazole or fosravuconazole alone, have reported evidence greater than 85% for early parasite clearance (negative PCR) after 2 to 4 weeks of treatment with benznidazole alone or in association with posaconazole or fosravuconazole, an effect sustained during the 12-month follow-up.³⁸⁵,⁵⁴¹,⁵⁴²

Later, the BENDITA clinical trial, a phase 2, multicenter, randomized, double-blind, double-dummy clinical trial, conducted in Bolivia, including individuals aged from 18 years to 50 years with the IFCD, has been published.⁵³¹ That clinical trial has evidenced that benznidazole induced effective antiparasite response (ranging from 83% to 89%), regardless of treatment duration (2 or 4 weeks), daily dosage (150mg or 300mg), or combination with fosravuconazole, being well tolerated (3% of severe adverse events) by adults with chronic disease.⁵³¹ Although not “definitive”, the study suggests the use of benznidazole as standard treatment and emphasizes the need for new studies with shorter drug regimens or with reduced benznidazole dosages.⁵³¹

These findings increase the evidence that new benznidazole regimens could expand access to etiological treatment and ensure greater tolerability.⁵³⁶ However, stronger evidence for the adoption of short-course therapy lacks. In this context, other ongoing clinical trials are as follows: the BETTY trial – a double-blind, noninferiority, randomized, controlled trial of short-course benznidazole treatment to reduce *T. cruzi* parasite load in women of reproductive age;⁵⁴⁷ the MULTIBENZ study – a phase II, randomized, noninferiority, double-blind, multicenter clinical trial assessing the efficacy and safety of different dosages of benznidazole for the treatment of adults with chronic CD;⁵⁴⁸ and the TESEO study - an open-label, randomized, prospective, phase-2 clinical trial assessing the safety and efficacy of new therapeutic schedules with benznidazole and nifurtimox for adults with chronic CD, in addition to assessing biomarkers.⁵⁴⁹

Despite the benznidazole's efficacy demonstrated in several studies, limitations regarding tolerability apply because of its relatively high toxicity, which can lead to the treatment interruption in approximately 10-25% of the cases.¹,²,⁵,⁸,⁵⁸,⁶⁰,⁳²⁴,⁵³⁶,⁵⁵⁰,⁵⁵¹ The mean incidence of adverse events associated with benznidazole use is approximately 50%, and cutaneous manifestations, gastrointestinal symptoms, and nervous system disorders have been the most common causes of treatment interruption.²,⁶⁰,³²⁴

Cutaneous adverse events are the most frequent, particularly urticarial dermatitis (45%) and rash (30%), and usually do not require treatment interruption because of their low intensity.⁸ Dermatitis begins by the end of the first week of treatment, and shows good response to treatment with antihistamines or small doses of oral corticosteroids.²,⁵⁸ In addition, gastrointestinal intolerance (13%), with nausea, vomiting and diarrhea, paresthesia (10%), and arthralgias (8%) can be found.⁸ Based on Amazonian case series in areas of higher occurrence of CD, the frequency of adverse events due to benznidazole was 20.2% in children and adolescents with CD in the acute phase. In these reports, the cutaneous alterations (rash, urticarial eruption or heterogeneous

desquamous exanthema, and angioneurotic edema) were the most commonly found (72%), followed by alopecia (3%), gastrointestinal disorders (2%), and insomnia (2%).²⁷⁹,²⁹¹

Peripheral polyneuropathy with paresthesia and pain in the lower limbs is most common in adults and usually begins by the end of the 60 day treatment, particularly after 50 days. It can have a significant impact on functioning and quality of life because it can last several months, even after treatment interruption, and does not respond well to treatment with anti-inflammatory drugs and polyvitamins. The occurrence of fever, adenomegaly, and oropharyngeal pain suggests early bone marrow depression and agranulocytosis, one of the most severe, although rare, effects of benznidazole. In such cases, significant leukopenia develops at the expense of segmented neutrophils (febrile neutropenia), indicating the need for immediate drug interruption and proscription. That is the reason why routine hemogram is indicated 3 weeks after beginning treatment.¹,²,⁸,⁵⁸

Briefly, despite all that, etiological treatment with benznidazole can be safely conducted in the context of PHC. A protocol by the Doctors Without Borders has shown consistent results, because up to 89.8% of the individuals treated could conclude the treatment, although 56.0% developed an adverse event.⁵⁸ The success achieved was associated with close monitoring of the cases, which strengthened surveillance, as well as counseling with qualified information and timely identification of adverse events with their management, leading to a lower dropout rate,⁵⁸ reinforcing the importance of longitudinal care.⁴⁴

In the context of pharmaceutical care, the protocol of benznidazole dispensation at intervals of approximately 7 days is recommended, which can increase use safety by enabling a closer and qualified follow-up, with timely detection and registry of adverse events.⁵⁸ Considering the chronic nature of CD, the pharmacotherapeutic follow-up enables, in addition to etiological treatment, the recognition of events associated with other drugs used, improving adhesion to treatment and quality of life.⁵,⁴³,⁴⁴,⁵³⁶,⁵⁵²

In the case of intolerance to benznidazole, nifurtimox can be recommended. It is available as tablets of 120mg (adults) and 30mg (children).¹,²,⁸,⁵³⁴,⁵³⁵ In 2020, the FDA/USA approved its use for the treatment of CD in children under the age of 18 years,⁵³⁴,⁵³⁵ extending access to treatment based on evidence available.⁵

Nifurtimox has gastrointestinal absorption, hepatic metabolization via cytochrome P450, and preferential renal elimination.¹,⁵³⁴,⁵³⁵ Nifurtimox is not available in the pharmaceutical market in Brazil, its provision being regulated by a standard protocol of the Health Surveillance Secretariat of the Ministry of Health via PAHO, according to specific demand, usually related to suspicion or confirmation of resistance or intolerance to benznidazole.²

In adults, nifurtimox is used at the dosage of 10mg/kg/day orally, in three daily doses for 60 days. In children, the recommended dosage is 15 mg/kg/day orally, also in three daily doses for 60 days.²,⁵³⁴,⁵³⁵ The CHICO study, a clinical prospective, controlled trial to assess the efficacy and safety of a new pediatric formulation of nifurtimox for children with
# Guidelines

CD aged between 0 and 17 years after 1 year of treatment, has confirmed that the 60-day treatment regimen was more effective than the same dosage for 30 days.⁵³

With nifurtimox, the mean frequency of adverse events is approximately 85%, the most frequent being gastrointestinal intolerance, such as anorexia and weight loss (60%), rheumatological events, such as arthralgias (35%), and cutaneous manifestations (15%).⁸ In the USA, of 243 individuals being treated, 222 (91.4%) reported at least one adverse event (total of 1155 adverse events, median of 4 per patient). The categories of adverse events reported were gastrointestinal (68.7%), neurological (60.5%), and constitutional (46.5%), and the most reported were nausea (50.6%), anorexia (46.1%), weight loss (35.0%), headache (33.3%), and abdominal pain (23.1%). At least 90% of the patients of all age ranges studied (under 18 years, 18-50 years, and over 50 years) reported adverse events.⁵⁴ Of 1042 adverse events with available data regarding severity, 680 (65.3%) were mild, 254 (24.4%) were moderate, and 108 (10.4%) were severe. The most frequent severe adverse events were depression (22.6%), peripheral neuropathy (18.5%), paresthesia (17.9%), and dizziness/vertigo (17.2%).

The proportion of individuals with at least one severe adverse event was higher among individuals over the age of 50 years (31.8%) as compared to those aged 18-50 years (18.1%).⁵⁴

Based on a comparative analysis of adverse effects, the 2019 PAHO guidelines for the diagnosis and treatment of CD reported no substantial difference between benznidazole and nifurtimox considering the evidence analyzed and expertise of PAHO's technical panel. However, specific profiles of predominant adverse events were recognized, nifurtimox being associated mainly with weight loss and psychiatric adverse effects, while benznidazole was associated with cutaneous and neurological reactions.⁶⁰ The adverse events and toxicity of nifurtimox stand out as reduced digestive tolerance, reflected by anorexia, nausea, and vomiting, with weight loss and psychiatric disorders most frequent in adults.¹,²,⁸,⁵³⁴,⁵³⁶,⁵⁵⁴

For both antiparasite drugs, ensuring clinical monitoring of their use is fundamental for the assessment and timely management of adverse events, with emphasis on tolerability.¹,²,⁸,⁵⁸,⁵³⁵,⁵³⁶ Chart 9.1 summarizes the major adverse effects of benznidazole and the proper management of each situation.

<table><caption>Chart 9.1 – Adverse effects of benznidazole and recommended management for each situation.</caption><thead><tr><th colspan="7">BENZNIDAZOLE</th></tr><tr><th>Adverse effects</th><th>Appearance</th><th>Characteristics</th><th>Location</th><th>Intensity</th><th>Management</th><th>Additional measures</th></tr></thead><tbody><tr><td>Dermatopathy due to hypersensitivity is the most frequent. It is NEITHER dose-dependent NOR related to <i>T. cruzi</i> infection. Recovery without sequelae</td><td>10th day of treatment, but can occur earlier or later</td><td>Non bullous erythema polymorphe, pruriginous, followed by desquamation. Onycholysis and angioneurotic edema rarely occur<br/>Rare reports of Stevens-Johnson syndrome</td><td>Focal (restricted to the tegument) or generalized</td><td>Mild (usually focal)<br/>Moderate (focal or generalized)<br/>Severe, usually accompanied by fever and lymphadenomegaly or Stevens-Johnson syndrome</td><td>Continue treatment<br/>Continue treatment and associate corticosteroid (prednisone) at a low dose. Interrupt if worsening occurs<br/>Interrupt treatment. Use corticosteroid</td><td>Specific treatment for dehydration and cutaneous desquamation<br/>Hospitalization according to clinical findings</td></tr><tr><td>Peripheral polyneuropathy. Dose-dependent, of slow regression (months)</td><td>End of treatment</td><td>Pain and paresthesia</td><td>Plantar (more frequent) and palmar regions</td><td>Mild to moderate</td><td>Interrupt treatment</td><td>General treatment for peripheral polyneuropathy</td></tr><tr><td>Ageusia (rare). Recovery without sequelae</td><td>End of treatment</td><td>Total or partial loss of taste</td><td>-</td><td>-</td><td>Interrupt treatment</td><td>-</td></tr><tr><td>Bone marrow depression and recovery without sequelae</td><td>Between the 20th and 30th days of treatment</td><td>Fever, adenomegaly, and sore throat can indicate leukopenia with neutropenia of varied degrees, which can reach agranulocytosis</td><td>-</td><td>-</td><td>Interrupt treatment</td><td>General treatment for bone marrow depression</td></tr></tbody></table>

Digestive intolerance (rare) is controlled by use of medication for gastritis and peptic ulcers. Severe hepatic impairment is rare. Renal impairment has not been observed.

Adapted from the 2º Consenso Brasileiro em DC, 2015 (Dias, 2016)² and Protocolo Clínico e Diretrizes Terapêuticas em DC, 2018 (Brazil, 2018).⁸
## 9.3. Etiological Treatment of Individuals with Chagas Disease

As already mentioned in another chapter of this guideline, considering the natural history of CD, most individuals with established infection remain asymptomatic throughout life. In the acute phase, 90% of the classical vectorial transmission cases remain asymptomatic or oligosymptomatic, and, of the 10% with evidence of clinical syndrome, less than half progress to more severe forms or death.²,⁷,⁴⁶,⁵⁵⁵ In oral transmission contexts (outbreaks and familial micro epidemics), in 75% to 100% of the cases, mild clinical syndrome occurs, as in children, or evident illness with prolonged febrile syndrome is observed.²⁷⁹,⁵⁵⁶

It is worth noting that the lesions derived from the *T. cruzi* infection in the acute phase depend exclusively on the presence of the parasite, while, in the chronic phase, these lesions are partially explained by the parasite persistence in the tissues and the immune response to the parasite.¹,⁵,³⁸,⁴⁶,³²³

The chronic phase of CD includes the indeterminate form (asymptomatic) and the cardiac, digestive, and cardiodigestive forms.²,⁴⁶ In the chronic phase, approximately 60-70% of the cases remain asymptomatic, while 30-40% progress to the disease's clinical forms usually after several years,³²,⁴⁶,⁵³⁹ with some potentially severe complications, particularly the cardiovascular ones, associated with high morbidity and mortality.¹,²,⁷,⁴⁶,²⁹⁷,⁴⁸⁸ Treatment, when indicated in the chronic phase, is aimed at reducing the parasitemia levels, preventing the appearance or progression of lesions in target organs, in addition to preventing transmission.¹,²,²⁹⁷,³¹⁸,³²²

The response to etiological treatment, confirmed in parasitological terms, varies and depends on the following factors: age at the time of diagnosis; disease's phase and duration; complementary tests used to assess therapeutic efficacy; post-treatment follow-up duration; associated conditions; and susceptibility of the different *T. cruzi* lineages (Tcl to TcVI) to antiparasite drugs.³⁸,²⁴⁸,³⁷⁹,⁵³⁸,⁵⁵⁰,⁵⁵⁷,⁵⁵⁸ These aspects reinforce the importance of following all cases up, independently of the place of treatment in the health care network.

Thus, the etiological treatment of an individual with CD should be conducted according to the individual's characteristics and the disease's clinical form, as shown in Chart 9.2.²,⁸

## 9.4. Acute Infection

In the acute phase of CD, the grade of recommendation of the etiological treatment for all cases (children, adolescents, and adults) is 'strong', even with level of evidence B of moderate quality regarding the benefit of the trypanocidal effect.⁶⁰ The treatment should be performed as early as possible after the infection is diagnosed, independently of the *T. cruzi* transmission mode, considering the potential benefits.¹,²,⁵,⁸,³²,⁶⁰,⁵⁵³,⁵⁵⁶,⁵⁵⁹-⁵⁶²

In the acute phase, despite the moderate level of scientific evidence and limited certainty regarding clinical outcomes, the treatment has high efficacy, increases the likelihood of serological and/or parasite tests becoming negative, in addition to improving the potentially severe clinical syndrome of the acute phase, thus, preventing progression to the manifest chronic form by reducing damages to specific organs.⁸,⁴¹,⁴⁴,²⁹¹,⁵⁵⁶,⁵⁶⁰,⁵⁶²-⁵⁶⁵ Considering the association of nontreated acute CD with mortality in up to 5% of diagnosed cases⁵⁵⁹ and the potential progression to the chronic phase in all cases, potential benefits are much superior regarding adverse events, which are mostly mild.⁶⁰,⁵⁵⁵

Thus, even in asymptomatic cases or when diagnostic confirmation is impossible, but suspicion persists (compatible clinical syndrome and epidemiological link, evidence of individuals living with infected individuals or exposed to triatomines, or suspicion of oral or congenital transmission), empirical treatment can be considered.⁸

Therefore, the intervention should be adopted by health managers as a health policy in most situations, given that most healthcare professionals agree with the recommendation of that treatment and that most individuals affected, when informed, want to undergo the intervention.

<table><caption>Chart 9.2 – Recommendations for etiological treatment of Chagas disease according to disease phase or clinical form and age group.</caption><thead><tr><th>Phase/form of CD</th><th>Age group</th><th>Etiological treatment</th></tr></thead><tbody><tr><td rowspan="2">Acute or congenital</td><td rowspan="2">All age groups</td><td>1<sup>st</sup> line: benznidazole</td></tr><tr><td>2<sup>nd</sup> line: nifurtimox</td></tr><tr><td rowspan="2">Children (≤ 12 years) and adolescents (13-18 years)</td><td rowspan="2"></td><td>1<sup>st</sup> line: benznidazole</td></tr><tr><td>2<sup>nd</sup> line: nifurtimox</td></tr><tr><td rowspan="2">Chronic indeterminate or digestive</td><td>Adults &lt; 50 years</td><td>1<sup>st</sup> line: benznidazole<br/>Do not use nifurtimox</td></tr><tr><td>Adults ≥ 50 years</td><td>Shared decision-making: possibility of treatment,<br/>if there is no contraindication<br/>1<sup>st</sup> line: benznidazole<br/>Do not use nifurtimox</td></tr><tr><td>Not advanced chronic cardiac (stage: B1*)</td><td>All age groups</td><td>Shared decision-making: possibility of treatment,<br/>if there is no contraindication<br/>1<sup>st</sup> line: benznidazole<br/>Do not use nifurtimox</td></tr><tr><td>Chronic cardiac or digestive (advanced phase)</td><td>All age groups</td><td>Do not treat</td></tr></tbody></table>

<footnote>*See Table 5.2 for the cardiopathy stages. Adapted from Protocolo Clínico e Diretrizes Terapêuticas em DC, 2018 (Brazil, 2018).⁸</footnote>
# Guidelines

For pregnant women, at any gestational age, with severe acute clinical syndrome related to myocarditis or meningoencephalitis, antiparasite treatment should be indicated independently of the gestational age, because of high maternal morbidity and mortality.⁸ In addition, even with level of evidence C, this indication is justified by the associated high risk (20-70%) of congenital transmission, with potential impact on the health of the neonates, and considering that the rare reports of etiological treatment during pregnancy would be associated with small evidence of malformations.²,⁵⁷,⁸⁶,⁵⁹⁵

However, pregnant women in the acute phase of CD without clinical severity should ideally wait for the second gestational trimester to undergo etiological treatment. Despite the potential benefit of reducing neonatal CD, the occasional occurrence of perinatal mortality or fetal malformation is uncertain. Thus, counseling about the risks and benefits of the etiological treatment should be performed, with shared decision, knowing that, in some cases, non-treatment is justifiable.²,⁸

## 9.5. Congenital Infection

Similarly to individuals with acute infection, those diagnosed with CD through congenital transmission should receive etiological treatment. In such cases, the grade of recommendation is 'strong', independently of the diagnosis being established by use of parasitological methods still in the first weeks, or conventional serological tests, 9 months after birth.¹⁻³,⁵,⁸,⁵⁷,⁶⁰,⁸⁶,¹¹²,⁵⁵³,⁵⁵⁹,⁵⁶⁶

This strong recommendation, despite the moderate quality of the evidence available (level B) favoring trypanocidal treatment, is based on both the predictable benefits in a potentially severe clinical situation and the higher likelihood of actual cure of the infection.¹,²,⁸,⁶⁰

The etiological treatment of an individual in the chronic phase of suspected congenital transmission should be performed considering the current age, the time of *T. cruzi* infection, and the disease's clinical stage.² These aspects will be detailed in the following sections. It is worth noting that, given the current evidence about CD and the relevance of epidemiological surveillance of chronic cases in Brazil, expanding access to health care is strategic, as is the development of comprehensive healthcare beyond etiological treatment, always keeping in mind the possibility of mother-to-child transmission.

## 9.6. Children and Adolescents with Chronic Infection

For this population, the etiological treatment has grade of recommendation 'strong' and level of evidence B.⁶⁰ For this management, it is worth emphasizing the potential benefits in a more severe epidemiological context, in addition to the likelihood of influencing, with treatment, outcomes such as turning serology and parasitemia negative.⁵,⁸,⁶⁰,³⁷⁵,³⁷⁶,⁵⁷⁶,⁵⁸⁶

Antiparasite treatment is indicated to all children (aged 12 years or less) and adolescents (aged 13 to 18 years) diagnosed with the IFCD, considering the higher likelihood of turning serology negative, which indicates proper response to therapy.¹,²,⁵,⁸,⁶⁰,³⁷⁵,³⁷⁶,⁵⁷⁷ This decision is based

on significant benefits regarding the reduction of damages to specific organs, without increasing the risk for adverse effects given the better tolerance to antiparasite drugs in those age groups.⁶⁰

In addition, the longer life expectancy of that population justifies that the treatment might be more effective in children as compared to adults.⁸ Cohorts with long-term follow-up using conventional serological methods, such as cure control with a mean follow-up of over 10 years for each case, and conducted in the Amazon context have shown the success of the etiological treatment in this population. In these cohorts, the treatment caused minimal complications with potential for chronicity, despite the persistence of reactive serology.²⁹¹

However, evidence relative to prevention of the disease's clinical manifestations with the use of benznidazole is limited by the short follow-up period of the studies, and that is even more limited for nifurtimox, which should remain as a therapeutic alternative.²,⁸ In addition, the use of nifurtimox can be considered a valid alternative, particularly in cases involving children, adolescents, and young adults with recent infection in the presence of intolerance to benznidazole.²,⁸,⁵³⁴

## 9.7. Women of Reproductive Age with Chronic Infection

For women of reproductive age (15 to 49 years) with chronic *T. cruzi* infection, the grade of recommendation for the etiological treatment with benznidazole is 'strong', considering the additional strategic benefit of controlling congenital transmission of CD.²,⁵,⁸,⁶⁰,⁸⁶,⁸⁹,¹¹²,⁵⁶⁹⁻⁵⁷²

Antiparasite treatment reduces significantly the likelihood of congenital transmission, and neither fetal nor neonatal adverse events have been observed.⁸,⁶⁰,⁸⁶,⁸⁹,⁵⁵⁹,⁵⁶⁹,⁵⁷⁰,⁵⁷² Thus, even with level of evidence B, with moderate certainty regarding the risk/benefit analysis, the grade of recommendation for the treatment was established as 'strong'.⁶⁰ In addition, the effective use of contraceptive methods systematically and correctly should be recommended to these women during the entire trypanocidal treatment period, and pregnancy should be ruled out before beginning treatment.²,⁸,⁴¹,⁶⁰,⁸⁹,⁵⁶⁹,⁵⁷⁰,⁵⁷² In endemic areas, these women should be systematically advised and assessed regarding the presence of triatomines, which should be eliminated from the households and their vicinities to prevent reinfection.

For pregnant women with chronic CD, treatment is not recommended given that the risk of congenital transmission is low, around 1.5% to 2% in Brazil.²,⁴⁶,⁵⁷,⁸⁶,⁵⁵⁹ However, pregnant women with acute and severe CD, expressed as myocarditis or meningoencephalitis, or even in the acute phase of non-severe disease diagnosed in the first trimester should be carefully assessed and the decision regarding etiological treatment should be shared, individualized, as previously discussed.⁸

In the Brazilian Amazonian region, where acute infections predominate, vertical transmission has been reported due to lack of knowledge about the pregnant status in contexts of outbreak or familial microepidemics,
with some very good documentation on congenital infection even after beginning maternal treatment with benznidazole.²⁷⁹,⁵⁵⁶

Finally, it is worth noting the important international initiative, the 'CUIDA Chagas', to which the Brazilian Ministry of Health adhered, involving Bolivia, Colombia, and Paraguay, in addition to five Brazilian states (Bahia, Goiás, Minas Gerais, Pará, and Rio Grande do Sul). The project began in 2022 and includes diagnostic and therapeutic measures and models for the elimination of the vertical transmission of CD among women of reproductive age chronically infected with *T. cruzi*, to be assessed over four years. One of the relevant objectives of this international consortium is to assess, in a randomized controlled study, whether a shorter trypanocidal therapeutic regimen with benznidazole (two weeks) is at least as effective as the usual one (60 days) and whether it has fewer adverse effects.⁵⁷³

## 9.8. Adults with Chronic Infection

The potential benefit of etiological treatment for all adults with chronic CD is not supported by a strong recommendation with high level of evidence for that indication, nor generically for any clinical-epidemiological situation.⁸,⁶⁰ This recommendation has, thus, a conditional level depending on the case analyzed, given the limited evidence available for some populations.⁶⁰ However, in such cases, aspects relative to the principle of asymmetry (if the potential benefit exceeds the risk of adverse effects) should be considered. Thus, this decision should be shared between the physician, health team, individual affected and family, depending on the phase of infection, and patient's age and clinical conditions.¹,²,⁵,⁸

It is worth noting that, as reported for adolescents, for adults of any age with recently acquired infection, regardless of the transmission mode, the grade of recommendation for treatment is 'strong', with level of evidence B.⁶⁰

Considering the stratification defined in the research plan of a significant number of consistent studies to assess etiological treatment, this document established the age cutoff point of 50 years, as in other national and international reference documents.²,⁵,⁸ It is worth noting that the PAHO clinical practice guidelines published in 2018 did not adopt that age stratification, considering the questions: 'Which is the safest and most effective therapy for adults with chronic *T. cruzi* infection with/without lesions in specific organs?' For cases in the IFCD, etiological treatment was established as 'conditional' with level of evidence 'weak', while, for cases with lesions in organs, the treatment was not recommended, with moderate level of evidence. The methodological procedures of the PAHO guidelines were developed from systematic reviews and primary studies published up to August 2017 (PubMed, EMBASE, Cochrane) and manual research with analysis using the GRADE system.²⁷,⁶⁰

Since 2017, new studies have been published increasing the body of evidence and demarcating the establishment of

the recommendations present in this document, expanding the opportunity of access to treatment of *T. cruzi* infection.

In adults up to 50 years of age with the IFCD, treatment is recommended, considering that its advantages seem to exceed the disadvantages, and that there is more evident benefit regarding cardiac disease prevention.²,⁸,³⁸,³¹⁸,³²⁰-³²³,³⁷⁹,⁵⁷⁴ The recommendation is strong with level of evidence B, considering more recent studies recognizing that the etiological treatment can reduce the risk of long-term cardiac disease,²,⁶⁰,²⁹⁷,³¹⁸,³²¹-³²⁵,⁵⁴² even without clear evidence about the impact on mortality.⁸,⁶⁰,⁵⁷⁵-⁵⁷⁷ The probability of negative parasitemia in the short run is higher, while non-reagent serology is observed only in the long run.³⁸,⁴¹,⁶⁰,³¹⁸,³²⁴,⁵⁴²,⁵⁵⁷,⁵⁷⁸,⁵⁷⁹ However, the treatment can be associated with considerable risk for adverse events, which are mostly mild and minimized by use of qualified monitoring,⁵⁸,⁶⁰,³¹⁸,³²³,⁵³⁶ but in some cases are sufficiently severe to cause therapy interruption.

In individuals aged 50 years and older in the chronic phase of CD, the benefit of etiological treatment in the IFCD has an even higher grade of uncertainty, leading to a conditional recommendation for etiological treatment with level of evidence C.¹,²,⁵,⁶⁰,³¹⁸,³²²-³²⁵,⁵⁴²,⁵⁷⁹

As previously shown, the factor 'age' should be relativized in terms of etiological treatment and particularly considered for individuals with recent infection (for example, in epidemiological contexts of oral or blood transfusion transmission in which age is an independent factor of clinical evolution) or who were infected during adulthood with no comorbidities and in a clear process of demographic transition in the Brazilian society, with longer life expectancy.²,⁸ Usually, these perspectives indicate the possibility of conditional recommendation for etiological treatment in this population.

For adults with determined chronic forms in initial non-advanced phases (cardiac and digestive), the indication for etiological treatment should be a shared decision, with information about potential benefits and risks, thus offering the possibility of treatment, being 'treating with benznidazole' or 'not' valid alternatives, if no contraindication applies. In such cases, the recommendation of etiological treatment is conditional, with level of evidence C.¹,²,⁵,⁸,⁶⁰,³¹⁸,³²²,³²³,⁵⁴² The initial phases of the CCCD consist in only ECG changes (ventricular repolarization disorder, VE, RBBB, LAFB, first-degree AVB), with global systolic ventricular function preserved or slightly reduced (LVEF > 40%), and stages B1 and B2 of HF without severe arrhythmias.¹,²,⁸,³¹⁸,³²²,³²³

Etiological treatment can be considered independently of the diagnosis of isolated or associated chronic digestive form, that is, cardiodigestive disease,⁸ because the treatment is aimed at preventing cardiac damage. For patients with digestive disorders installed and even in those without the digestive form, there is no evidence that the antiparasite treatment prevents or delays the appearance or progression of megaesophagus and megacolon.⁸,⁵⁵⁹ Some patients with megaesophagus can have the efficacy of treatment with benznidazole hindered by interference
# Guidelines

with its ingestion or absorption.²,⁸ Although the diagnosis of chronic digestive form represents no contraindication to etiological treatment, clinical rehabilitation, dilation or surgical correction of megaesophagus is recommended before initiating the etiological treatment to ensure drug transit and absorption in the digestive tract.²,⁸,⁴⁴

When chronic cardiomyopathy is already installed, usually there is no evidence that the etiological treatment might significantly impact evolution to death or progression of cardiac disease, although it increases the probability of eliminating parasitemia, assessed by PCR.⁶⁰,³²³⁻³²⁵ Thus, antiparasite treatment should not be recommended for individuals with advanced organ lesions (stages C and D of cardiac forms) or very old.¹,²,⁵,⁸,³²,⁶⁰,³¹⁸,³²²,³²⁴,⁵⁴⁰,⁵⁷⁹ In such cases, the etiological treatment does not change the disease's natural history, can be associated with increased risk for severe adverse events, in addition to inducing direct and indirect costs for the individuals affected and their families, thus expanding their social vulnerability.

So, all efforts should be made for timely diagnosis and etiological treatment in cases of CD to prevent disease progression. It should be noted that the annual risk of mortality in CCCD is considerable (7.9%; 95% CI, 6.3-10.1%) and mainly attributed to cardiovascular disorders, especially in the presence of low LVEF and classified as stages C and C/D.⁴⁴⁸

Individuals with severe megaesophagus, which hinders the proper absorption of the trypanocidal agent, are in a special situation. In the absence of manifest cardiopathy or in its initial stage, in which the etiological treatment is aimed at preventing cardiovascular disease progression, etiological treatment can be indicated after surgery for megaesophagus.² In such situation, the indication for etiological treatment would have 'conditional' recommendation and level of evidence C.

Notably the careful analysis of the results from the BENEFIT trial, the most comprehensive RCT on trypanocidal therapy in patients with CCCD (mostly nonadvanced), enabled the identification of some relevant aspects. In fact, when considering the entire population, involving patients from five Latin American countries (Brazil, Argentina, Colombia, Bolivia, and El Salvador), the etiological treatment with benznidazole had no favorable impact on mortality and other severe outcomes from cardiomyopathy.³²⁴ In addition, when compared to placebo, there was no benefit regarding regional ventricular dysfunction, an early alteration often detected in those individuals and with a poor prognosis.³²⁴

However, the global analysis of that study's results has been criticized, which might have prevented the duly appreciation of some methodological flaws with relevant implications in the applicability of the study's results.³²⁵ For example, as compared to the group treated with placebo, the group treated with benznidazole showed a statistically significant reduction in the rate of hospitalization due to cardiovascular causes, which, although highly valued in several studies involving

patients with HF, was not even discussed in the primary analysis of the BENEFIT trial.³²⁴

There are other aspects that deserve critical appreciation. The initial analysis of the BENEFIT trial subgroups was arbitrary, non-prespecified, and did not follow defensible criteria, being, therefore, biased.³²⁴,³²⁵ In contrast, post-hoc analysis of that study's results evidenced that the etiological treatment effect on Brazilians patients (40% of that study's sample) might have been positive, particularly when comparing the results in the Brazilian subgroup with those observed in the other four countries participating in BENEFIT.³²⁵

In the meantime, this possibility should be considered the generator of a hypothesis to be tested in a subsequent study specifically designed to prove or refute it. The corollary hypothesis of the interpretation that the etiological treatment is more effective when applied to Brazilians already with CCCD is biologically plausible and can be supported by the predominance of TcII parasite genotype observed in Brazil, which can be more sensitive to benznidazole as compared to other *T. cruzi* strains and nifurtimox. There are scientific reasons why the treatment of patients based on trypanocidal drugs (including those in the validation phase) should consider both the parasite genetic diversity²⁴⁸ and the complex interaction of several parasite lineages with the human host, resulting in several clinical expression forms.²⁵⁰

Based on these considerations, the 'conditional' grade of recommendation for offering etiological treatment to individuals already with non-advanced CCCD in Brazil can be considered with emphasis on the higher potential benefit than that in other countries. Finally, it should be pointed out the significant severity of CD and the need for timely diagnosis and comprehensive care to individuals with cardiopathy, based on qualified clinical management.¹,²,⁴⁴,⁶⁰,³²⁴

In addition, considering current evidence about etiological treatment as well as relevance of epidemiological surveillance, mandatory reporting of cases of chronic CD should be implemented, enabling the extension of access to diagnosis and treatment to more individuals affected.⁸,⁴⁴,⁵⁶,⁹¹,⁹⁴,¹¹³

## 9.9. Reactivation of Chagas Disease

The RCD consists in the aggravation of *T. cruzi* chronic infection, characterized by an increase in parasitemia (similar to that of the disease's acute phase) and immune system's inability to control the infection, usually associated with drug-induced immunosuppression – transplantations, immunosuppressive treatments – or coinfection with HIV.¹,²,⁸,⁸³,⁸⁴,⁵⁸⁰

The RCD is associated with high morbidity and mortality because of the central nervous system infection and myocarditis and has a critical impact on quality of life.²,⁸,⁸³,⁸⁴ The prevalence of RCD based on parasitemia in immunosuppressed individuals with CD, without trypanocidal prophylaxis, was approximately 28%, and distributed as follows: 1.8% in liver transplanted individuals;
23.3% in bone marrow transplanted; 27.3% in kidney transplanted; 30.9% in heart transplanted; and 39.6% in individuals with HIV infection/AIDS.⁶⁰

If RCD occurs, the etiological treatment indicated for the acute phase of CD should be initiated.²,⁸,⁸³,⁸⁴ Despite the moderate level of evidence (B), the recommendation is classified as strong, because the antiparasite drugs can have benefits in preventing the consequences of reactivation, as well as in its control and even recurrence.⁵,⁶⁰,⁸⁴,⁵⁸⁰-⁵⁸⁴

In HIV infection, in the presence of chronic CD without reactivation and no previous etiological treatment, patients should preferably be treated with benznidazole and have their immune status assessed because of the increased risk for immune reconstitution inflammatory syndrome.⁸,⁸³,⁸⁴

For transplanted patients with RCD, the same treatment schedule used for non-transplanted ones is indicated, benznidazole being the preferred alternative due to its better profile regarding adverse events and the largest experience with its use in the country.²,⁸ There is no consistent evidence to recommend secondary prophylaxis for transplanted individuals, but that can be indicated in selected cases, particularly the most immunosuppressed ones.⁸,⁶⁰

Usually, the etiological treatment can contribute to prevent clinical complications, such as cardiopathy, and should be considered with the same recommendations and levels of evidence used in other situations related to non-immunosuppressed individuals with chronic CD.⁸,⁸⁴

For both HIV-infected and transplanted individuals, qPCR can aid in clinical monitoring; however, its routine recommendation is yet to be defined.⁸,⁶⁰,⁵⁸⁰ It is worth noting that the RCD episodes can occur repeatedly and should be treated when documented, justifying regular parasitological monitoring while the immunosuppression condition is maintained.²,⁸³,⁸⁴

## 9.10. Accidental Infection

In laboratory accidents with biological material contaminated with *T. cruzi* and at high risk for disease transmission, such as sharp instruments, contact with non-intact mucosa or skin, or manipulation of biological material with live parasites (*T. cruzi* culture samples, biological samples of cases with high parasitemia, and infected material from autopsy, vectors, and experimental animals), primary prophylaxis is indicated, beginning with benznidazole at the dosage of 7 to 10 mg/kg immediately after the accident and for 10 days.¹,²,⁵⁵⁸,⁵⁸⁵ The grade of recommendation for this management is 'strong', despite the limited level of evidence (C), but considering the principle of asymmetry.²,⁵,⁸,⁶⁰,⁸³

Serological tests should be performed before initiating treatment and on the 20th, 40th, and 60th days after treatment for monitoring an occasional seroconversion.² If the serological tests are reagent, the conventional antiparasite treatment should be performed as previously described for the acute phase. In situations of minimum risk, such as the mere superficial contact with blood of individuals in the chronic phase of CD, drug prophylaxis

is not indicated and serological tests are recommended immediately after and on the 20th, 40th, and 60th days after the accident.² If seroconversion occurs, the conventional treatment for the acute phase of CD should be initiated with post-therapeutic monitoring as recommended for the acute phase. If the serology remains positive after treatment, a possible therapeutic failure should be documented for a new treatment with benznidazole or nifurtimox.¹,²,⁸³,⁵³⁴

## 9.11. Assessment of Chagas Disease Cure After Etiological Treatment

In a disease with only two therapeutic options with consistent indications for use, there is no evidence available about complementary methods to assess, in the routine context of health services, the etiological treatment effect on parasite elimination, particularly in the chronic phase.¹,⁸,⁴¹,⁶⁰ Ensuring access to treatment is fundamental, which has a clear social function given the negligence regarding individuals affected by the disease. Usually, arguments associated with adverse events and not being able to document cure are used to justify non-treatment in the SUS. As a chronic condition, CD requires comprehensive and longitudinal care to all individuals affected.

There is no complementary method to confirm advancement for cure (which would be considered gold-standard), making serological and molecular tests, even with all technical limitations, potentially available and useful methods to assess response to antiparasite treatment in the chronic phase.⁸,³⁸,⁶⁰,³⁷⁹

Thus, there is no evidence regarding the need for follow-up with serological control after a complete treatment or retreatment course.⁸,⁶⁰ The quality of the evidence supporting the use of negative serology to replace clinically relevant outcomes is 'low' or 'very low', actually representing an indirect outcome.⁸,⁶⁰

In addition, in adults, it may take more than two decades for a serological test to become negative after treatment,³⁸,³⁷⁹,⁵⁷⁷ which usually occurs in only 1/3 of the cases, depending on different factors, such as age at the time of treatment, time elapsed between treatment and follow-up, and the area in which the infection occurred.⁵⁸⁶ For children and adolescents, a serological test can become negative within 5 years in 3/4 of the cases.³⁷⁶,⁵⁵³,⁵⁵⁶,⁵⁶⁰-⁵⁶⁷ Analyses of children and adolescents with acute CD in the Amazon region indicate persistent reactive serological tests in almost 55% of the cases, in a mean follow-up of approximately 11 years after treatment, and 17% of the cases showed sustained negative serological responses.²⁹¹

Although some studies have suggested the use of PCR to monitor and control therapeutic response, the sensitivity of PCR is variable⁵⁸⁷ and it is not available as a validated and agreed technique in the SUS, restricting its applicability to research activities.⁸,⁴⁶ However, a positive PCR in the first 24 months after treatment indicates the possibility of therapeutic failure.⁵⁶²,⁵⁸⁷

The percentages of cure reported by several studies after antiparasite treatment of CD differ, but the importance of the etiological treatment is acknowledged in both the acute phase and some clinical forms of chronic disease.²,⁸,⁵⁵⁷
# Guidelines

In addition, even with all the already mentioned limitations of the current antiparasite therapy, elimination of parasitemia can be achieved in some scenarios,¹,²,⁸,⁴⁶,³²⁰,³²⁴,⁵⁴⁰,⁵⁷⁴,⁵⁷⁹ making the usefulness of etiological treatment unquestionable in a considerable part of the clinical situations, independently of the demonstration of cure, except for acute CD. Thus, for the chronic phase of CD, defining the criterion for cure has no practical use, contributing greatly as a strong barrier to access.

## 9.11.1. Where to Treat an Individual with Chagas Disease

In addition to the technical-scientific leadership in CD management, Brazil has a great differential as compared to most CD endemic countries: the SUS, the Brazilian public health system that provides comprehensive and democratic health care, a right ensured to Brazilian citizens by the 1988 Federal Constitution. Thus, the SUS provides access to diagnosis and treatment for CD in the country.²,⁴⁹,¹¹³

However, despite the favorable context and referential available from ordinances, guidelines, consensus, and PCDT itself,¹⁻³,⁸,⁶⁰ with clinical benefits in the short and long run, diagnosis, treatment, and surveillance of chronic CD could not be consistently implemented in the Brazilian territory.¹¹³ Questions such as centralization of actions, surveillance and control of CD have contributed to this situation. Thus, a global unified overview of the current development stage of initiatives to control CD in Brazil, despite the achievements over almost 120 years, indicates the need for implementation and integration of the measures in the PCDT with sustained surveillance of CD and adhesion to national and international guidelines.¹¹³

Particularities of the SUS healthcare network should be considered, recognizing, however, that etiological treatment of the *T. cruzi* infection is feasible, safe, and operationally practicable in the PHC.²,⁸,⁴⁴,⁵⁸,⁹⁴,¹¹³,⁵²⁹,⁵³³,⁵³⁶ The PHC can assume the management of individuals with non-severe acute CD, the IFCD, or even the chronic forms (cardiac, digestive, or cardiodigestive) of stable non-severe disease, as well as of pregnant women with chronic CD without comorbidities.⁸,⁴⁴ There is evidence that family doctors and their teams, knowing the particularities of the medications and disease, can clinically manage those cases.²,⁴⁴,⁵⁸,⁵³³

Depending on the severity of the clinical conditions, mainly in the acute phase or RCD, as well as decompensated chronic forms, support might be needed for the plan of care or referral to more specialized healthcare units, or even hospitalization in sporadic conditions.²,⁸,⁴⁴,⁹⁴

Table 9.1 summarizes the recommendations for etiological treatment of *T. cruzi* infection in different contexts of CD, according to the strength of recommendation and level of evidence, based on the GRADE system.

When this chapter was being concluded, the update of an old systematic review and respective meta-analysis was published regarding studies on the etiological treatment with benznidazole for individuals with *T. cruzi* infection.⁵⁸⁸ The essential conclusions of that publication are in accordance with the recommendations presented in this guideline. Finally, in addition to the search for more solid scientific evidence, all efforts should be made to ensure access to diagnosis and etiological treatment of CD in the national health systems.

<table><caption>**Table 9.1 – Recommendation for etiological treatment in different contexts of Chagas disease, according to the grade of recommendation and level of evidence (adapted from the GRADE system)**</caption><thead><tr><th>ETIOLOGICAL TREATMENT OF CHAGAS DISEASE<br>Trypanosoma cruzi infection</th><th>Recommendation grade</th><th>Level of evidence</th></tr></thead><tbody><tr><td>Children with acute infection</td><td>Strong</td><td>B</td></tr><tr><td>Children with congenital infection</td><td>Strong</td><td>B</td></tr><tr><td>Adolescents and adults in general with acute or recently acquired infection</td><td>Strong</td><td>B</td></tr><tr><td>Children and adolescents with chronic infection</td><td>Strong</td><td>B</td></tr><tr><td>Women of reproductive age with chronic infection</td><td>Strong</td><td>B</td></tr><tr><td>Individuals in general with reactivation of chronic infection (HIV/AIDS or other immunosuppressive conditions, including transplantation)</td><td>Strong</td><td>B</td></tr><tr><td>Individuals in general with accidental infection with biological material in laboratory or healthcare settings</td><td>Strong</td><td>C</td></tr><tr><td>Pregnant women with severe acute clinical syndrome - myocarditis or meningoencephalitis</td><td>Strong</td><td>C</td></tr><tr><td>Adults aged &lt; 50 years with chronic infection (chronic indeterminate form)</td><td>Strong</td><td>B</td></tr><tr><td>Adults aged ≥ 50 years with chronic infection (chronic indeterminate form)</td><td>Conditional</td><td>C</td></tr><tr><td>Adults in general with chronic infection (initial phases of chronic determined forms – non-advanced cardiac and digestive)</td><td>Conditional</td><td>C</td></tr><tr><td>Individuals in general with chronic infection and advanced organ injury in the digestive form (not associated with advanced cardiac disease), after surgical repair</td><td>Conditional</td><td>C</td></tr><tr><td>Individuals in general with chronic infection and advanced organ injury in the chronic cardiac or digestive form (associated with advanced cardiac disease) should not be treated</td><td>Strong</td><td>C</td></tr></tbody></table>
# 10. Therapeutic Management of Ventricular Dysfunction and Heart Failure

## 10.1. Pharmacological Resources

### 10.1.1. Heart Failure Classification

Our recommendations prioritize patients with reduced LVEF, because most pharmacological therapies have been validated in that scenario. The difference between the scientific study inclusion criteria and the clinical indication should be understood. Studies usually select patients with lower LVEF (< 35% or < 40%) to optimize the incidence of the outcome of interest, increasing the statistical power. Because the magnitude of the absolute effect (NNT) is more relevant in high-risk patients (that is, we should treat few patients to obtain a benefit) and no plausible reason is identified for the occurrence of qualitative interaction (disappearance of effect) when a certain LVEF cutoff point is exceeded, we chose to generalize our recommendations for the use of the essential drugs to treat HF in patients with LVEF < 55%, preventing excessive categorization.

However, it is worth considering the existence of a continuum of inverse relation between LVEF and therapeutic benefit, that is, the lower the LVEF value, the higher the absolute benefit of the therapy proposed. To simplify, strong recommendations for LVEF ≤ 40% will be 'conditional' for LVEF between 41% and 54%. In addition, we consider that in patients with segmental contractility abnormalities, but without global ventricular dysfunction, who are classified as stage B of HF, the body of evidence is still insufficient to promote any recommendation.

### 10.1.2. Maximum Dosage of Medications

This guideline does not support the obstinacy in reaching the maximum dosage of medications to the detriment of polypharmacy, preferring to emphasize the individualization of each drug best dosage for each patient. The rationale for that is based on some justifications. The dosage proposed or even reached for patients in clinical trials is part of a scientific strategy, aimed to generate contrast between groups and test conceptual hypotheses. Once the concept has been demonstrated, it should be applied in an individualized way, weighting benefits and risks. Thus, choosing a drug dosage relates more to clinical reasoning than to evidence. There are no convincing scientific data about the magnitude of the incremental benefit related to maximum dosage (versus weighted dosage) and whether it overcomes unintentional consequences. In addition, tolerability and adverse effects are underestimated in RCTs of efficacy, in which ideal candidates for the treatment in question are usually selected and care is better controlled. Thus, we do not transform efficacy into effectiveness by standardizing the maximum. The increase in effectiveness results from careful individualization.

### 10.1.3. The Contemporary Patient

As the life of patients with CCCD and HF is prolonged, they tend to suffer from other diseases that appear with aging.

Recently, a RCT of patients with CCCD from a single center (FIOCRUZ) has reported mean age of 65 years, mean body mass index of 27.4 kg/m², and SAH in 1/3 of the patients,⁵⁸⁹ differing, thus, from studies showing younger individuals frequently without comorbidities. Also, there is a possibility of a different clinical course of HF from CD as compared to HF from ischemic and idiopathic dilated etiologies.⁵⁹⁰ That might be due to the more severe autonomic dysfunction, higher density of ventricular arrhythmia and intracardiac blocks, greater load of myocardial fibrosis, most frequent RV impairment, and higher degree of cardiac sphericity/remodeling and myocardial inflammation - factors that could interfere with response to standard pharmacological treatment.⁵⁹¹,⁵⁹²

The worst clinical course, merely from the statistical viewpoint, suggests greater absolute benefit from treatment with level B of evidence when compared to the target populations of the studies, and should not implicate in the violation of the principle of indirect evidence, that is, extrapolation.

The previously cited study from FIOCRUZ⁵⁸⁹ is part of a comprehensive initiative of translational research aimed at experimentally and clinically exploring hypotheses about the potential benefit of supplementation with nutrients, such as selenium, and antagonism to inflammatory factors to change the CCCD course.⁵⁹³ The primordial value of these incipient investigations might reside in their strongly pathophysiology-based hypothesis on the inflammatory nature of CCCD. Only guided research will be able to provide the responses to those interventions.

### 10.1.4. Literature Review

For each drug or class of drug used in the treatment of HF, a systematic review of the literature up to August 22, 2021, has been conducted, aiming to answer the following PICO question of EBM: "Are these drugs effective to relieve symptoms and/or reduce mortality of symptomatic patients with systolic HF secondary to CCCD, with a safety profile similar to that for HF of other etiologies?". The following *Medical Subject Headings* (MESH) were used: "beta-blockers, spironolactone, sacubitril-valartan, ivabradine, sodium-glucose transporter 2 inhibitors", "heart failure" or "Chagas disease", with limit of the type of publication ("clinical trial"). The MedLine/PubMed, Lilacs, Web of Science and EMBASE databases were used as search sources.

### 10.1.5. Pharmacological Therapy

#### 10.1.5.1. Diuretics

The diuretic therapy in HF is misunderstood in its magnitude of effect. The lack of RCTs comparing diuretic versus placebo can cause the mistaken impression that, differently from beta-blockers or ACEIs, loop diuretics do not reduce mortality. This lack of studies could be due to the absence of equipoise for the type of patient whose prognostic benefit was validated
for other therapies. That is, in HF, the administration of a diuretic is a therapy of extreme plausibility, corresponding to the parachute paradigm,³¹ justifying, in this guideline, level of evidence C regarding pharmacological indication. Thus, we strongly recommend diuretic therapy for HF with moderate to severe ejection fraction reduction and for cases with mild ejection fraction reduction, in the presence of pulmonary or systemic congestion.

## 10.1.5.2. Renin-Angiotensin-Aldosterone System Inhibitors

Several clinical trials of quality have shown that, in patients with HF and reduced LVEF, several ACEI reduce relevant outcomes of morbidity and mortality.⁵⁹⁴⁻⁵⁹⁶ In addition, these drugs can be replaced by angiotensin II receptor blockers (ARBs) in case of poor tolerability.⁵⁹⁷ However, in HF of CCCD, there is no direct evidence of benefit from RCT performed specifically in that population. Thus, the evidence regarding the use of ACEI in CCCD is indirect, originated from studies of excellent quality that tested the efficacy of that treatment in the most common types of cardiomyopathy (ischemic and idiopathic dilated) (level B). Considering that ejection fraction is a prognostic continuum, rather than a binary, dichotomic variable, the higher the degree of ventricular dysfunction, the higher the absolute benefit. Thus, the recommendation is strong for patients with HF and LVEF ≤ 40%, while 'conditional' for patients with HF with mildly reduced ejection fraction (HFmrEF).

Studies with a very reduced number of patients, assessing captopril and enalapril in HF of CCCD, have evidenced a reduction in the sympathetic neuro-humoral activation and in serum angiotensin levels, in addition to improvement of diastolic dysfunction and ventricular remodeling.⁵⁹⁸⁻⁶⁰⁰ These patients frequently have reduced systolic blood pressure, and can become more hypotensive and symptomatic with the introduction of ACEI or ARB, which should be gradually up-titrated, aiming to reduce the dosages of diuretics when the patient no longer has edema.

In recent decades, international guidelines have emphasized the search for the therapeutic target dosage of ACEI or ARB for patients with HF with reduced ejection fraction (HFrEF), which can be misleading and a limitation in clinical practice, considering that patients with CCCD are prone to symptomatic arterial hypotension. Thus, we should search for the best tolerated dosage and proceed to slow titration in that group of patients subject to dosage limitations.⁶⁰¹

### 10.1.5.3. Beta-blockers

The first experiences using beta-blockers for the treatment of patients with HF date back to the 1970s, when some researchers assessed the effect of the drug on seven patients with cardiomyopathy, advanced HF, and tachycardia.⁶⁰² On that occasion, one patient received alprenolol, 50 mg twice a day, and the others, practolol at dosages ranging from 50 mg to 400 mg, twice a day. The authors reported clinical improvement, cardiomegaly reduction, and ventricular function improvement assessed on phonocardiogram, ECHO, apexcardiogram, and carotid pulse curve. Despite the

promising results reported by the Swedish group, the use of beta-blockers in HF was only properly assessed in the 1990s.

The seminal study suggesting benefit from beta-blockers in HFrEF was the *U.S. Carvedilol Heart Failure Study*,⁶⁰³ which randomized 1094 patients for carvedilol or placebo and showed a reduction in mortality.

In the past 25 years of clinical investigation, beta-blockers were consolidated for the treatment of HF. In a meta-analysis⁶⁰⁴ involving 10 clinical trials and 18 254 patients with HFrEF, beta-blockers reduced global mortality by 27%.

Importantly, patients with HFrEF can get worse in the initial phase of the beta-blocker treatment.²¹ Thus, surveillance is mandatory regarding worsening, appearance of bradycardia, cardiac block, and hypotension, especially in the first weeks of treatment adjustment.

In the context of HF, that is especially important, because patients with CCCD are more susceptible to the occurrence of those adverse manifestations when on beta-blockers. Although CCCD has not been included in large multicenter studies investigating beta-blockers and mortality, in addition to the peculiarities of that syndrome, known to be associated with dysregulation of the autonomic nervous system, as reviewed in another chapter of this guideline, there is no biological plausibility in questioning the benefit of beta-adrenergic block in the treatment of HFrEF from CCCD.

Analysis of a small group of patients (n = 68) with HF due to CD from the REMADHE trial⁶⁰⁵ has compared those on beta-blockers with those not using those drugs. Despite the limitation of the small sample size for direct comparison, the authors have suggested beneficial effects of beta-blockers related to increased survival (non-adjusted p = 0.05, that is, borderline). It is worth noting that, in that study, the use of beta-blocker was not randomized, with a high risk of confounding bias due to indication.

We consider that the evidence regarding the use of beta-blockers for patients with HFrEF due to CD is indirect, originating from studies of excellent quality that tested the efficacy of that treatment in the most common types of cardiomyopathy (level B). Considering that ejection fraction is a prognostic continuum, rather than a dichotomic variable, more severe systolic dysfunction tends to be associated with a higher absolute benefit. Thus, the recommendation is strong for patients with HF and LVEF ≤ 40% and conditional for patients with HFmrEF.

Severe ventricular arrhythmia requiring amiodarone is a special case. The association of a beta-blocker with amiodarone can be inappropriate because of bradycardia and/or QT interval prolongation. We consider that, in such context, there is no proof that a beta-blocker should be the priority. This is a case to base decision-making on clinical judgement, and the physician should decide which drug to prescribe initially based on the arrhythmia severity (favors amiodarone) versus the HF severity (favors a beta-blocker). This is a rare situation in which this guideline recognizes the limitation of static recommendations, being open to the dynamism of medical thinking grounded in rationality and evidence (not to be mistaken with concepts of efficacy allegedly based, in a naïve and inconsequential way, only on the infamous "clinical eye").
#### 10.1.5.4. Spironolactone

Spironolactone is the preferable antagonist of mineralocorticoid receptor, the major binding site of aldosterone and responsible for its physiological actions, with direct involvement in the pathophysiology of HF.

In general, spironolactone is indicated for all patients with symptomatic HF and LVEF ≤ 35%, regardless of the concomitant use of ACEI, ARB, or beta-blockers, except for patients with serum creatinine > 2.5mg/dL or creatinine clearance < 30mL/min/1.73m², or serum potassium level > 5.0mEq/L.

The RALES study, a randomized, double-blind, placebo-controlled study supporting that indication, was published in 1999. That study assessed if the use of spironolactone, at dosages ranging from 25 mg to 50 mg, would be better than placebo for HFrEF (≤ 35%) and functional class III-IV, with the concomitant use of ACEI and furosemide.⁶⁰⁶ The study was early terminated after 24 months, with a satisfactory number of outcomes to indicate precision and interim analysis showing 35% reduction in the risk of death.

Patients with creatinine > 2.5 mg/dL were excluded, and the incidence of hyperkalemia was minimum in both groups. This should be highlighted because the Canadian study of epidemiological surveillance reported that the spironolactone prescription rate increased substantially after the publication of the RALES study, followed by an increase in the morbidity and mortality rates associated with hyperkalemia.⁶⁰⁷ Thus, observation of the contraindication criteria for spironolactone use and judicious surveillance are essential in the clinical management of patients on that drug.

Despite the minimum representation of CCD in the RALES study (and this was not specified in its baseline table), there is no biological plausibility to question the potential benefit of aldosterone block regarding HFrEF progression in CCD. Thus, we consider it a good application of level of evidence B (indirect, good quality). Considering indications and contraindications, the recommendation should be strong for patients with symptomatic CCCD, LVEF ≤ 40%, creatinine ≤ 2.5mg/dL, and serum potassium ≤ 5.0mEq/dL, while conditional for patients with HFmrEF.

#### 10.1.5.5. Ivabradine

Ivabradine is a selective funny channels current blocker and, thus, an inhibitor of the PM activity in the sinus node, resulting in selective reduction of HR without changing hemodynamic parameters, such as blood pressure or myocardial contractility, and without interfering in intracardiac electrical conduction.

The SHIFT trial, a randomized, double-blind, placebo-controlled clinical study, published in 2010, supports the use of ivabradine for HF.⁶⁰⁸ In that study, ivabradine was tested at the maximum dosage of 7.5 mg, twice a day, in patients with HF (LVEF ≤ 35%), sinus rhythm, and HR > 70bpm, regardless of the use of beta-blockers when tolerated. The study reported a 26% relative reduction in the risk of hospitalization, in addition to mortality from HF of 26%.

A substudy of the SHIFT trial,²¹⁵ by use of post-hoc analysis, has assessed 38 patients with HF due to CD, assigned to two groups as follows: ivabradine group, 20 patients; placebo group, 18 patients. Although patients with CCCD usually have a worse prognosis, with higher prevalence of RBBB, lower blood pressure levels, higher rate of use of diuretics, spironolactone, digoxin, and lower rate of use of ACEI/ARB and beta-blockers, when compared to the general population of the SHIFT study, ivabradine did not associate with higher prevalence of severe bradycardia, AVB, hypotension, or syncope. In addition, ivabradine was effective in reducing the HR of those patients and improving the HF functional class.

A therapeutic recommendation should not be based on exploratory study. In the SHIFT trial, the CCCD was not well represented. However, generalization does not depend only on representativeness, and we recognize no probable mechanism of interaction that raises the suspicion that the CD etiology changes the effect of therapy with ivabradine to the point of losing efficacy as shown in the general set of patients included in the SHIFT trial. Thus, we defined the level of evidence B, which represents indirect evidence of good quality for the use of ivabradine in patients with CCCD and HF. The strength of the recommendation should be 'conditional' because it depends on the perception that HR is high when the beta-blocker dosage cannot be increased. Given this specificity, we chose not to extend that indication to patients with LVEF > 40%.

#### 10.1.5.6. Digoxin

When reviewing the literature, we identified no study assessing the safety and efficacy of digoxin in CD. Thus, we will use indirect scientific evidence that digoxin improves symptoms and reduces hospitalizations.⁶⁰⁹,⁶¹⁰ In clinical practice, the drug can be indicated for patients in NYHA functional class III and IV, despite optimized treatment with other drugs, especially in the presence of AF with high ventricular response.

Regarding digitalis, the therapeutic dosage is very close to the toxic one, which increases the potential for adverse effects, because of the conduction system involvement, causing bradyarrhythmias, AVB, and other general clinical manifestations.

#### 10.1.5.7. Sacubitril-valsartan

Sacubitril-valsartan is a drug combination of a neprilysin inhibitor (increases the availability of atrial natriuretic peptides), sacubitril, and a traditional angiotensin II receptor blocker, valsartan. The PARADIGM-HF trial was the major study for scientific validation of this drug combination⁶¹¹ as compared to enalapril. Although it can be considered a precise study with a low risk of bias, showing a 20% relative risk reduction with that drug association in the primary combined outcome of hospitalization from HF and cardiovascular death, there was margin for scientific questioning of its conceptual design.⁶¹² With a heterodox comparator, the study was not able to differentiate whether the benefit found was due to the innovative molecule in the treatment (sacubitril) or whether it was due to the inadequate difference regarding the dosages
# Guidelines

of the traditional angiotensin system inhibitors (valsartan, at the maximum daily dosage of 320 mg versus enalapril at the submaximal, maybe insufficient, daily dosage of 20 mg). Another limitation was the presence of a run-in phase in a phase III study, which overestimates the applicability of the treatment, because it selected in advance the patients who tolerate a more intense vasodilating therapy.

From the PARADIGM-HF trial publication, many cardiologists began to perceive the sacubitril-valsartan combination as more effective than the traditional vasodilation with ACEI, which has influenced recommendations of guidelines on HF. In Brazil, the sacubitril-valsartan use was approved in May 2017 by the Brazilian Health Surveillance Agency (ANVISA), and, in August 2019, it was incorporated into the SUS.⁶¹³

In addition, unlike the homogeneous benefit verified with several angiotensin-II system inhibitors studied, the sacubitril-valsartan combination did not prove superiority in other contexts. Two examples of that are the PARAGON-HF study,⁶¹⁴ of patients with HF and LVEF ≥ 45%, and the PARADISE-MI study, of HF complicating acute myocardial infarction.⁶¹⁵ In both scenarios, the results could not reject the null hypothesis in their primary analyses. It is worth noting that the PARADISE-MI study was the only to compare sacubitril-valsartan with the proper dosage of ACEI (10 mg/day of ramipril).

Thus, we consider inappropriate an indication based on the expectation that this drug combination is superior to the traditional therapy. On the other hand, there is no evidence that this therapy is harmful, making it a valid therapeutic alternative, if the doctor wants to modify a standard treatment due to clinical or logistic reason. It is worth noting that the report supporting the incorporation of sacubitril-valsartan into SUS has estimated an incremental cost-effectiveness ratio of R$22.769 per year of life gained with quality.⁶¹³

Regarding the indication of that combination for patients with HF caused by CCCD, in addition to the literature review technique already mentioned, Google Scholar was used to search the gray literature for any reference that could clarify this issue, and annals of medical congresses were assessed for this information.

Thus, a case series conducted with patients with CCCD treated with sacubitril-valsartan in a reference hospital for that disease in Brazil has reported, after 6 months, symptomatic improvement of the individuals.⁶¹⁶

In a prospective observational study of 136 consecutive patients with HF in a single university-affiliated hospital center, including the HF etiologies of ICM, CCCD, and idiopathic cardiomyopathy,⁶¹⁷ the authors reported that up to 44% of the patients had the major criteria of exclusion of the PARADIGM-HF trial. In addition, they reported that the lower blood pressure levels, common in CCCD, could lead to underuse of some drugs in this context.

Another study, assessing the proportion of patients with CCCD randomized to two recent clinical trials (PARADIGM-HF and ATMOSPHERE), has found that only 7.6% of the randomized patients in Latin America had that etiology.⁵⁹²

A post-hoc analysis of a subgroup of the PARADIGM-HF trial has suggested that sacubitril-valsartan, as compared to enalapril, could lead to a similar or even higher (37%)

reduction in death and hospitalization of patients with CCCD, as compared to those with HF of other etiologies, despite lack of statistical significance and imprecision of estimates of effect.⁶¹⁸ The ongoing PARACHUTE trial (ClinicalTrials.gov Identifier: NCT04023227) is an exclusive study of patients with HF from CCCD. Similarly to the PARADIGM trial,⁶¹¹ the comparators are not the orthodox ones and the effect of sacubitril associated with the maximized dosage of valsartan will be compared to that of enalapril at a non-maximum dosage, of 20 mg daily.

In summary, patients with CCCD have not been well represented in the sacubitril-valsartan studies. Thus, although we presented some evidence on the use of that therapy for patients with HF caused by CCCD, it is not enough to support a recommendation, due to its exploratory character. However, the evidence serves to exemplify the principle of indirect evidence: generalization does not depend only on representativeness, and we do not recognize any probable mechanism of interaction that makes us suspect that the etiology of the heart disease modifies the effect of this therapy. Therefore, we defined that the sacubitril-valsartan treatment for patients with HFrEF and CCCD is an alternative with level of evidence B, although not a superior innovation as compared to the traditional treatment. Regarding recommendation, this should not be the preferred treatment, but considered an alternative when clinical judgement suggests the need for therapeutic change (conditional recommendation). This indication is not to be extended to patients with LVEF > 40%.

### 10.1.5.8. Sodium-Glucose Cotransporter-2 Inhibitors

In recent years, this class of drugs brought enthusiasm to the scientific community because of the demonstration of incremental benefit to the traditional treatment, in terms of prognostic improvement of HF and renal dysfunction. In this chapter, we revise whether the level of evidence is proportional to the enthusiasm and translate it into decision-making in the context of HF from CCCD.

Sodium-glucose cotransporter-2 (SGLT2) inhibitors are drugs originally tested for the treatment of hyperglycemia in patients with type 2 diabetes mellitus. The SGLT2 acts in the proximal convoluted tubule and responds for 90% of the reabsorption of the filtered glucose in the glomerulus. The SGLT2 inhibitors promote renal excretion of glucose, which is the mechanism of its glycemia reduction effect.⁶¹⁹ There were two initial observations regarding the intermediate effects: first, the efficacy of those inhibitors as glycemia reductors in individuals with diabetes is modest, with mean reductions in glycated hemoglobin ranging from 0.4% to 1.1%, as compared to placebo;⁶¹⁹⁻⁶²¹ second, they promote consistent body weight reduction as compared to other antidiabetic drugs.⁶²²,⁶²³

The initial strategy of the manufacturers of this class of drugs was to assess its safety for individuals with diabetes, focusing on macrovascular outcomes (cardiovascular death, myocardial infarction, and stroke) and using counterintuitive approach of non-inferiority testing compared to placebo. Although counterintuitive, the deviation of the null hypothesis to a value different from zero is a suitable method to test safety, because a tolerance interval of adverse effect can be justified based on a demonstrated benefit.
Non-inferiority compared to placebo (safety) has been confirmed in several studies of that class of drugs,⁶²⁴⁻⁶²⁶ which is scientifically valid. However, the clinical question persisted: in the absence of proven incremental benefit, would the demonstration of safety be a justification to recommend the addition of that treatment to patients with diabetes?

Then an apparent reduction in the HF-related outcomes in the groups treated was perceived. These were the secondary outcomes of studies, except for the DECLARE-TIMI 58 clinical trial,⁶²⁴ which comprised a primary efficacy outcome if the non-inferiority hypothesis for severe event was demonstrated. SGLT2 inhibitors promote natriuresis, osmotic diuresis (due to glucosuria), and weight loss, mechanisms that a priori increase the probability of the benefit demonstrated. Based on those results, the hypothesis that the SGLT2 inhibitors improved the prognosis of patients with HFrEF was tested.

Thus, clinical trials with SGLT2 inhibitors began to be conducted in patients with symptomatic HF, regardless of the presence of type 2 diabetes mellitus. The DAPA-HF⁶²⁷ and EMPEROR-Reduced⁶²⁸ studies have assessed the effect of dapagliflozin and empagliflozin, respectively, on the incidence of the combined outcome of cardiovascular death and hospitalization from HF, as compared to placebo, in patients with HFrEF. The first to be published, the DAPA-HF study, included 4744 patients with HF and LVEF ≤ 40%, in NYHA functional class II to IV, already using optimized pharmacological therapy, and elevation of NT-proBNP levels. Diabetes mellitus was present in 42% of the sample and 99% of the individuals were in functional class II or III at the time of randomization. The HF etiology was nonischemic in 44% of the cases, with no mention to CD, although it was a multicontinental clinical trial, with approximately 17% of the participants recruited in Latin-American centers.⁶²⁷

The patients were randomized for the use of dapagliflozin, 10 mg/day, or placebo, at a 1:1 ratio. After a median 18-month follow-up, dapagliflozin was associated with a reduction in the risk for the primary outcome, which included cardiovascular death and hospitalization from HF (386 versus 502 events, respectively; HR 0.74; 95% CI, 0.65-0.85). The benefit was observed in both components of the primary outcome and proved to be consistent in the pre-specified analyses in different subgroups, such as the presence or absence of type 2 diabetes mellitus.⁶²⁷ In addition, there was a reduction in the risk of all-cause death in the group treated with dapagliflozin versus the placebo group (276 vs 329; HR, 0.83; 95% CI, 0.71-0.97).

A substudy of the DAPA-HF study has more carefully assessed the potential influence of the HF etiology, classified as ischemic and nonischemic (hypertensive, idiopathic, "other", and unknown cause), regarding the benefit of dapagliflozin on the primary outcome and found no change of effect.⁶²⁹

The safety profile of dapagliflozin was satisfactory, with low incidence of severe adverse events. Importantly, when assessing the eligibility criteria of the DAPA-HF study, systolic blood pressure < 95 mm Hg and glomerular filtration rate < 30mL/min/1.73m² were exclusion criteria.

The EMPEROR-Reduced study, published in 2020,⁶²⁸ investigated the effect of empagliflozin, as compared to placebo, in patients with HFrEF (≤ 40%) on optimized

medical therapy and defined inclusion criteria and primary outcome similar to those of the DAPA-HF study. However, the 3730 participants of the study (50% with type 2 diabetes mellitus) showed higher mean levels of atrial natriuretic peptides and lower mean LVEF values as compared to those of the dapagliflozin study sample. Once more, CD was not represented as an etiology of HF, although 34% of the study participants had been recruited in Latin-American countries. After a median 16-month follow-up, empagliflozin reduced by 25% the combined risk of hospitalization from HF and cardiovascular death as compared to placebo (19.4% versus 24.7%; HR 0.75; 95% CI, 0.65-0.86). However, differently from the DAPA-HF study, that benefit seemed to be basically due to reduction in hospitalizations from HF. In the pre-specified subgroup analyses, the effect of empagliflozin on the primary outcome remained consistent.⁶²⁸

Similarly to the DAPA-HF study, in the EMPEROR-Reduced study, patients on SGLT2 inhibitor showed lower values of systolic blood pressure, body weight, and NT-proBNP after a 1-year follow-up as compared to baseline values.

More recently, the EMPEROR-Preserved trial⁶³⁰ has extended the investigation of empagliflozin to patients with HFmrEF (≥ 40%). The relative reduction in the risk of events was similar to that observed in patients with LVEF ≤ 40%, which is expected, because an arbitrary limit of ejection fraction does not define two different diseases. Of note patients with HFmrEF have better prognosis, which reduces the absolute magnitude of the benefit: NNT of 19 in the first two studies with LVEF < 40% and NNT of 30 in the EMPEROR-Preserved trial.

Those studies have satisfactory statistical precision and low risk of bias. Thus, it seems adequate to state that there is effect of benefit, whose magnitude, represented by a 25% relative risk reduction, is at the level (marginal) of most therapies approved for HF. Therefore, from the pragmatic viewpoint, these drugs are safe and moderately beneficial.

Regarding cost-effectiveness, the recent incorporation of dapagliflozin into SUS was based on a report from the CONITEC presenting an economic model with incremental cost-effectiveness ratio of R$9296 per year of life saved with quality, being within an acceptable definition of efficiency.

However, there is one conceptual question: how much of the benefit of those drugs derives from diuretic therapy improvement versus how much of that is due specifically to the molecule innovation? There are reports of favorable effects of those drugs on intermediate outcomes, both metabolic and neuro-humoral, such as an increase in the circulating levels of vasodilators and a reduction in the levels of vasoconstrictors. However, clinical trials have not focused on the pertinent proof of concept that these are the effects that mediate the clinical benefit. None of them has generated a counterfactual (second control group) based on the diuretic therapy to answer the question: if a patient not receiving the innovative drug had the same level of diuresis improvement, would his outcome be different? This question could also be explored by use of mediation analysis (causal inference), with data from the clinical trials and a post-randomization mediator variable that represented the effect on diuresis. We have not detected this type of approach in the literature.
# Guidelines

Finally, how to translate our interpretation of the evidence into a recommendation of therapy with gliflozins in individuals with HF of CD? Once more, that subpopulation has not been represented in clinical trials. In accordance with data presented for other contexts, generalization does not depend only on representativeness, and we do not know any probable mechanism of interaction that raises the suspicion that the etiology of CCCD modifies the effect of that therapy to the point of loss of efficacy. Therefore, we defined that there is level of evidence B for HF from CCCD, that is, indirect and of good quality. Regarding the strength of recommendation, in the absence of the counterfactual that there is benefit beyond the diuretic effect, we chose a conditional recommendation for patients with HFrEF, and prescription should be based on clinical findings suggesting

the need for therapeutic increment.

The recommendations for the pharmacological treatment of HF in CCCD are shown in Table 10.1 and Figures 10.1 and 10.2.

## 10.2. Non-Pharmacological Resources

### 10.2.1. Cardiac transplantation

Despite all the advance observed in drug treatment, in intensive care, and surgical strategies, including the use of implantable cardiac devices, for the treatment of HF, this clinical syndrome persists with high morbidity and mortality and considerable economic impact on the health system, mainly in its more advanced phases.⁶³¹

<table><caption>**Table 10.1 – Recommendations for the pharmacological management of heart failure in CCCD**</caption><thead><tr><th>Heart failure with reduced ejection fraction (HFrEF): ≤ 40%</th><th>Recommendation grade</th><th>Level of evidence</th></tr></thead><tbody><tr><td>Loop diuretics to control systemic or pulmonary congestion</td><td>Strong</td><td>C</td></tr><tr><td>Thiazide diuretic associated with loop diuretic to control persistent systemic or pulmonary congestion</td><td>Strong</td><td>C</td></tr><tr><td>ACEI to reduce morbidity and mortality</td><td>Strong</td><td>B</td></tr><tr><td>ARB for patients intolerant to ACEI (cough/angioedema) to reduce morbidity and mortality</td><td>Strong</td><td>B</td></tr><tr><td>Sacubitril-valseran to replace ACEI/ARB for patients already on optimized triple therapy, who remain symptomatic (NYHA II or III), to reduce morbidity and mortality</td><td>Conditional</td><td>B</td></tr><tr><td>Carvedilol, metoprolol succinate, or bisoprolol to reduce morbidity and mortality in hemodynamically stable patients</td><td>Strong</td><td>B</td></tr><tr><td>Spirolactone associated with standard treatment with ACEI (or ARB) and BB to reduce morbidity and mortality (symptomatic CCCD, creatinine ≤ 2.5mg/dL, and serum potassium ≤ 5.0 mEq/dL)</td><td>Strong</td><td>B</td></tr><tr><td>Association of hydralazine and nitrate in patients with contraindication to ACEI/ARB (renal failure and/or hyperkalemia) to reduce morbidity and mortality</td><td>Conditional</td><td>B</td></tr><tr><td>Ivabradine for patients with optimized therapy, sinus rhythm, and HR > 70 bpm to reduce morbidity and mortality</td><td>Conditional</td><td>B</td></tr><tr><td>SGLT2 inhibitors (dapagliflozin or empagliflozin) for patients with or without diabetes, on optimized triple therapy, to reduce cardiovascular outcomes and progression to renal dysfunction</td><td>Conditional</td><td>B</td></tr><tr><td>Digoxin for symptomatic patients with AF and increased ventricular response, despite the use of BB, to reduce symptoms and hospitalizations</td><td>Conditional</td><td>B</td></tr><tr><td>Digoxin for symptomatic patients in sinus rhythm, despite optimized triple therapy, to reduce symptoms and hospitalizations</td><td>Conditional</td><td>B</td></tr></tbody></table><table><thead><tr><th>Heart failure with mildly reduced ejection fraction (HFmrEF): 41-54%</th><th>Recommendation grade</th><th>Level of evidence</th></tr></thead><tbody><tr><td>Loop diuretics to control systemic or pulmonary congestion</td><td>Strong</td><td>C</td></tr><tr><td>Thiazide diuretic associated with loop diuretic to control persistent systemic or pulmonary congestion</td><td>Strong</td><td>C</td></tr><tr><td>ACEI to reduce morbidity and mortality</td><td>Conditional</td><td>B</td></tr><tr><td>ARB for patients intolerant to ACEI (cough/angioedema) to reduce morbidity and mortality</td><td>Conditional</td><td>B</td></tr><tr><td>Carvedilol, metoprolol succinate, or bisoprolol to reduce morbidity and mortality</td><td>Conditional</td><td>B</td></tr><tr><td>Spirolactone associated with standard treatment with ACEI (or ARB) and BB to reduce morbidity and mortality</td><td>Conditional</td><td>B</td></tr><tr><td>Digoxin for symptomatic patients with AF and increased ventricular response, despite the use of BB, to reduce symptoms and hospitalizations</td><td>Conditional</td><td>B</td></tr></tbody></table>

CCCD: chronic cardiomyopathy of Chagas disease; BB: beta-blocker; ARB: angiotensin II receptor blocker; AF: atrial fibrillation; HR: heart rate; ACEI: angiotensin-converting-enzyme inhibitor; NYHA: New York Heart Association; SGLT2: sodium-glucose cotransporter-2.