Restrictive cardiomyopathy
Synonyms and keywords: Infiltrative cardiomyopathy; RCM; stiff heart; stiffening of the heart; heart stiffening; stiffened heart

# Overview
Restrictive cardiomyopathy (RCMP) is a rare form among other cardiomyopathies, characterized by increased stiffness of the ventricles in the presence of normal diastolic volume and normal ventricular wall thickness. It may be classified into primary i.e EMF(endomyocardial fibrosis),Lofflers endocarditis, Idiopathic restrictive cardiomyopathy and secondary i.e, infiltrative diseases(e.g., amyloidosis, sarcoidosis, and radiation carditis) and storage diseases (e.g., hemochromatosis, glycogen storage disorders, and Fabrys disease). Cardiac amyloidosis is the most common cause of restrictive cardiomyopathy. Mainly due to deposition of amyloid fibrils in the extracellular space and misfolding into -pleated sheets which are antiparallel to each other making them resistant to proteolysis, and also cause oxidative stress as a result leading to myocardial damage. Sarcoidosis characterized by noncaseating granulomas formation in various tissues including heart and hemochromatosis due to excessive accumulation of iron within the cells of various organs liver, pancreas, heart, and several endocrine glands leading to cirrhosis, diabetes, heart failure, skin pigmentation is also the common causes. Cardiac genes for desmin, -actin, troponin I and troponin T are involved in the pathogenesis of restrictive cardiomyopathy. Restrictive cardiomyopathy should be differentiated from dilated cardiomyopathy, hypertrophic cardiomyopathy, congestive heart failure. Restrictive cardiomyopathy is very rare among all other types and accounts for approximately 5% of all cases. Its prevalence varies depending on regionality, ethnicity, age, and gender. Amyloidosis affects men and women equally. The wild-type transthyretin amyloidosis is most often found in the elderly population. Common complications of restrictive cardiomyopathy include thromboembolism, rhythm abnormalities(dysrhythmias), cardiac cirrhosis, heart failure, pulmonary hypertension. Common symptoms include dyspnea, fatigue, palpitations, syncope. Jugular venous distension is noted sometimes with Kussmaul sign and Hepatojugular reflux.S3 and S4 gallops seen. ECG shows Low QRS voltages, conduction disturbances, nonspecific ST abnormalities. Transmitral spectral Doppler often shows restrictive filling pattern and Ejection fraction (EF) is normal. The main purpose of treatment in restrictive cardiomyopathy (RCM) is to reduce symptoms by decreasing the elevated filling pressures without significantly lowering the cardiac output.Pharmacologic therapy may include Beta blockers, Amiodarone, Cardioselective , Diuretics, Anticoagulants for patients with atrial fibrillation, Melphalan (for antiplasma cell therapy in systemic amyloidosis), Chemotherapy (in amyloidosis). Other approaches like Pacemaker implantation and endomyocardectomy are also available.

# Historical Perspective
- In 1957 for the first time Brigden coined the term cardiomyopathy to describe group of uncommon, non-coronary myocardial diseases.
- But later in 1961 Goodwin redefined cardiomyopathies as myocardial diseases of unknown cause. Infact he is the one who put them into 3 seperate entities dilated, hypertrophic and restrictive, which we are still using today.
- In 1980 World Health Organization (WHO) and International Society and Federation of Cardiology (ISFC) combinedly published a classification which included the three subgroups proposed by Goodwin.

# Classification
- There is no established system for the classification of restrictive cardiomyopathy 
- It may be classified into:
- Primary
EMF(endomyocardial fibrosis)
Lofflers endocarditis
Idiopathic restrictive cardiomyopathy
- EMF(endomyocardial fibrosis)
- Lofflers endocarditis
- Idiopathic restrictive cardiomyopathy
- Secondary
Infiltrative diseases(e.g., amyloidosis, sarcoidosis, and radiation carditis)
Storage diseases (e.g., hemochromatosis, glycogen storage disorders, and Fabrys disease)
- Infiltrative diseases(e.g., amyloidosis, sarcoidosis, and radiation carditis)
- Storage diseases (e.g., hemochromatosis, glycogen storage disorders, and Fabrys disease)

# Pathophysiology

## Pathogenesis
- The exact pathogenesis of restrictive cardiomyopathy is not completely understood.
- Mainly characterized by impaired ventricular filling and reduced diastolic volume of one or both ventricles, with either normal or near-normal systolic function.
- Hemodynamic abnormalities constitute the main pathological aspect of restrictive cardiomyopathy.
- The primary abnormality of restrictive cardiomyopathy is impaired myocardial relaxation along with interstitial fibrosis as well as calcifications.
- Restrictive filling can been seen which is due to higher diastolic pressure.

### Cardiac Amyloidosis
- It is the most common cause of restrictive cardiomyopathy(RCM).
- Mainly due to deposition of amyloid fibrils in the extracellular space and misfolding into -pleated sheets which are antiparallel to each other making them resistant to proteolysis, and also cause oxidative stress as a result leading to myocardial damage.

### Sarcoidosis
- Characterised by noncaseating granulomas formation in various tissues including heart.
- The usual location is basal septum, AV node, bundle of His, the ventricular free walls, and papillary muscles.
- Formation of granuloma includes 3 histological stages: edema, granulomatous infiltration, and fibrosis.

### Hemochromatosis
- Due to excessive accumulation of iron within the cells of various organs liver, pancreas, heart, and several endocrine glands leading to cirrhosis, diabetes, heart failure, skin pigmentation.

# Genetics
Genes involved in the pathogenesis of restrictive cardiomyopathy  include:
- Cardiac genes for desmin, -actin, troponin I and troponin T.
- Missense mutation (D190H) in the region of the cTnI gene (TNNI3).
- De novo mutations (R192H and K178E) in the TNNI3 gene.
- Mutations in the -cardiac actin (ACTC), -myosin heavy chain (-MHC), and cTnT (TNNT2) genes have been noticed to have etiological causes of  restrictive cardiomyopathy.

# Gross Pathology
On gross pathology, , , and  are characteristic findings of .

# Microscopic Pathology
On microscopic histopathological analysis, restrictive cardiomyopathy will show features suggestive of the cause.
- Cardiac Amyloidosis:
On H&E stain it shows the pink color and demonstrates apple-green birefringence when viewed under polarized light.
- On H&E stain it shows the pink color and demonstrates apple-green birefringence when viewed under polarized light.
- Sarcoidosis:
Consists of granulomas with macrophages and epithelioid histiocytes and lymphocytes.
- Consists of granulomas with macrophages and epithelioid histiocytes and lymphocytes.
- Niemann-Pick: foam cells are seen
- Mucopolysaccharidosis type II: glycosaminoglycans
- Hereditary hemochromatosis: Deposition of iron is seen
- Gaucher disease: Gaucher cells (lipid-laden macrophages) are seen

# Causes
The main Causes of restrictive cardiomyopathy are enlisted below:
- Amyloidosis (AL, ATTR, SSA)
- Sarcoidosis
- Hemochromatosis
- Eosinophilic myocardial disease
- Idiopathic RCM
- Progressive systemic sclerosis (scleroderma)
- Postradiation therapy (Hodgkin's lymphoma, breast cancer etc)
- Anderson Fabry disease
- Danon's disease
- Friedreich's ataxia
- Diabetic cardiomyopathy (restrictive phenotype)
- Drug induced (anthracycline toxicity, methysergide, ergotamine, mercurial agents, etc.)
- Mucopolysaccharidoses (Hurler's cardiomyopathy)
- Myocardial oxalosis
- Wegener's granulomatosis
- Metastatic malignancies

# Differentiating restrictive cardiomyopathy from Other Diseases
Restrictive cardiomyopathy should be differentiated from  dilated cardiomyopathy, hypertrophic cardiomyopathy, congestive heart failure ect ,

# Epidemiology and Demographics

## Incidence
Restrictive cardiomyopathy is very rare among all other types and accounts for approximately 5% of all cases.

## Prevalance
- Its prevalence varies depending on regionality, ethnicity, age, and gender.
- Amyloidosis: It affects men and women equally. The wild-type transthyretin amyloidosis is most often found in the elderly population.
- Sarcoidosis: More common in women than men. The highest prevalence is among black women. The highest incidence worldwide is in Japan.
- Hemochromatosis: Affects both men and women equally.
- Loffler endocarditis: More Common in tropical climates and sub-Saharan Africa.

# Risk Factors
- Any family history of restrictive cardiomyopathy
- Inherited diseases (such as hereditary hemochromatosis, Fabry disease, mutant-type  TTR amyloidosis, etc.)
- Increased number of blood transfusions leading to secondary hemochromatosis.
- Prior anthracycline use in childhood, exposure to other toxic agents.
- Eosinophilic syndrome or chronic parasitic infection
- Exposure to any radiation to the chest.

# Screening

# Natural History, Complications, and Prognosis

## Natural History
- The symptoms of (disease name) usually develop in the first/ second/ third decade of life, and start with symptoms such as ___.
- The symptoms of (disease name) typically develop ___ years after exposure to ___.
- If left untreated, % of patients with  may progress to develop , , and .

## Complications
- Common complications of restrictive cardiomyopathy include:
Thromboembolism
Rhythm abnormalities(dysrhythmias)
Cardiac cirrhosis
Heart failure
Pulmonary hypertension
- Thromboembolism
- Rhythm abnormalities(dysrhythmias)
- Cardiac cirrhosis
- Heart failure
- Pulmonary hypertension

## Prognosis
- Restrictive cardiomyopathy (RCM) has the worst prognosis among all types of cardiomyopathies.
- Prognosis is generally poor, and the 2/5-year mortality rate of patients is approximately 50% and 70%, respectively.
- There is an estimated 2-5 year survival rate after diagnosis.

# Diagnosis

## Diagnostic Study of Choice

## History and Symptoms
- The majority of patients with  are asymptomatic.
OR
- The hallmark of  is . A positive history of  and  is suggestive of . The most common symptoms of  include , , and .
- Symptoms of  include , , and .

## History
Patients with ] may have a positive history of:

## Common Symptoms
Common symptoms of include:
- Dyspnea
- Fatigue
- Limited exercise capacity
- Palpitations
- Syncope

## Less Common Symptoms
Less common symptoms of restrictive cardiomyopathy include
- Angina

## Physical Examination
Physical examination of patients with restrictive cardiomyopathy is usually abnormal with characteristic findings in cardiovascular and pulmonary systems.

## Appearance of the Patient
- Patients with restrictive cardiomyopathy usually appear normal.

## Vital Signs
They are usually with in normal limitis.

## Skin
- Skin examination of patients with restrictive cardiomyopathy is usually normal except in hemochromatosis which may show classic bronze skin

## HEENT
- HEENT examination of patients with restrictive cardiomyopathy  is usually normal.

## Neck
- Jugular venous distension is noted sometimes with kussmaul sign
- Hepatojugular reflux

## Lungs
- Fine/coarse crackles upon auscultation of the lung bases/apices unilaterally/bilaterally
- Rhonchi

## Heart
- S1
- S2
- S3
- S4
- Gallops

## Abdomen
- Hepatomegaly

## Back
- Back examination of patients with restrictive cardiomyopathy is usually normal.

## Genitourinary
- Genitourinary examination of patients with restrictive cardiomyopathy is usually normal.

## Neuromuscular
- Neuromuscular examination of patients with restrictive cardiomyopathy is usually normal.

## Extremities
- Peripheral edema of the lower extremities

## Laboratory Findings
- The laboratory findings depends on the cause of the cardiomyopathy.
- Hematocrit, serum electrolytes, blood urea nitrogen (BUN), creatinine, 24 hr urine total protein, and liver function should be assessed.
- Arterial blood gas (ABG) should be checked for possibility of hypoxia.
- Serum brain natriuretic peptide (BNP) or N-terminal pro-b-type natriuretic peptide (NT-proBNP) and troponin T are indicative of the heart failure.
- Other Specific lab findings will depend upon the cause (angiotensin converting enzyme (ACE) in sarcoidosis, complete blood count (CBC) with peripheral smear helping to establish eosinophilia in hypereosinophilic syndromes, serum iron concentrations, total iron-binding capacity and ferritin levels in hemocromatosis, immunoglobulin free light ,  chain testing, and serum and urine immunofixation in amyloidosis, etc.

## Electrocardiogram
Shown below is an example of restrictive cardiomyopathy with low voltage and  flipped anterior T waves.

## X-ray
A chest X-ray may show atrial dilatation most of the times.

## Echocardiography and Ultrasound
Echocardiography may be helpful in the diagnosis of restrictive cardiomyopathy. Findings on an echocardiography suggestive of restrictive cardiomyopathy include:
- Normal or increased wall thickness
- Transmitral spectral Doppler often shows restrictive filling pattern.
- Marked left or biatrial dilatation usually as a consequence of chronically elevated filling pressures.
- Ejection fraction (EF) is normal or near normal.
- The main purpose of echo is the differential diagnosis between constrictive pericarditis(CP) and resrictive cardiomyopathy(RCM).
- Both present as heart failure with normal-sized ventricles and preserved EF, dilated atria, and doppler findings of increased filling pressure often seen in restrictive cardiomyopathy.

## CT scan

## MRI
- Magnetic Resonance imaging and late gadolinium enhancement (LGE) is very helpful in providing information about anatomic structures, perfusion, ventricular function, as well as tissue characterization.
- Late gadolinium enhancement (LGE) depending on the pattern of scar formation can help the doctor in establishing the diagnosis to specific subtypes of restrictive cardiomyopathy(RCM).
- MRI can also quantify the myocardial iron load in patients with haemochromatosis or thalassemia who receive transfusions.

## Other Imaging Findings
- Radionuclide imaging using single-photon emission computed tomography (SPECT), or positron emission tomography (PET), is also used for the diagnostic work-up of amyloidosis.
- An increased myocardial uptake of Tc-99m pyrophosphate or Tc-99m 3,3-diphosphono-1,2-propanodicarboxylic acid helps to identify patients with familial transthyretin-related amyloidosis(ATTR) and also it can differentiate them from those with light chain amyloid(AL).
- Radionuclide imaging with 18fluorodeoxyglucose- (FDG-) PET is recently being used to assist in the diagnosis of cardiac sarcoidosis.
- Decrease in myocardial perfusion with enhanced 18FDG uptake is consistent with inflammation, while decreased perfusion with reduced 18FDG uptake is associated with scarring.

## Other Diagnostic Studies

# Treatment

## Medical Therapy
- Restrictive cardiomyopathy has no definitive treatment. But However, the ones directed at individual causes have been proven to be effective.
- The main purpose of treatment in restrictive cardiomyopathy (RCM) is to reduce symptoms by decreasing the elevated filling pressures without significantly lowering the cardiac output.
- Pharmacologic therapy may include:
Beta blockers
Amiodarone
Cardioselective calcium channel blockers
Diuretics
Anticoagulants for patients with atrial fibrillation
Digoxin (use with caution)
Melphalan (for antiplasma cell therapy in systemic amyloidosis)
Chemotherapy (in amyloidosis)
Corticosteroids, cytotoxic agents (eg, hydroxyurea), and interferon (in Loeffler endocarditis)
Chelation therapy or therapeutic phlebotomy (in hemochromatosis)
- Beta blockers
- Amiodarone
- Cardioselective calcium channel blockers
- Diuretics
- Anticoagulants for patients with atrial fibrillation
- Digoxin (use with caution)
- Melphalan (for antiplasma cell therapy in systemic amyloidosis)
- Chemotherapy (in amyloidosis)
- Corticosteroids, cytotoxic agents (eg, hydroxyurea), and interferon (in Loeffler endocarditis)
- Chelation therapy or therapeutic phlebotomy (in hemochromatosis)
- Other treatments:
Pacemaker implantation
Endomyocardectomy
Cardiac transplantation
Novel approches (eg, RNA interference or gene silencing molecules that target abnormal protein production in familial amyloidosis)
- Pacemaker implantation
- Endomyocardectomy
- Cardiac transplantation
- Novel approches (eg, RNA interference or gene silencing molecules that target abnormal protein production in familial amyloidosis)

## Surgery

## Primary Prevention

## Secondary Prevention