Spontaneous coronary artery dissection overview
Synonyms and keywords: SCAD

# Overview
Spontaneous coronary artery dissection (SCAD) is a rare but under recognized cause of acute coronary syndrome and sudden cardiac death, which predominantly affects young, healthy women with few or no traditional cardiovascular risk factors.Spontaneous coronary artery dissection (SCAD) was first described by Pretty in 1931 in which a 42-year-old woman presented with nausea and chest pain died unexpectedly due to rupture of a dissecting atheromatous aneurysm in the right coronary artery following repetitive retching and vomiting. In the post-morterm examination, heart muscle and valve appeared normal, and there was extensive hemorrhage between aorta and pulmonary artery secondary to coronary artery rupture presumably during the sudden and violent retching attack. Spontaneous coronary artery dissection can be classified based on angiographic appearance into type 1 (evident arterial wall stain with multiple radiolucent lumens), type 2 (diffuse smooth stenosis of varying severity), and type 3 lesions (focal or tubular stenosis mimicking atherosclerosis). At present, the pathophysiology of non-atherosclerotic spontaneous coronary artery dissection (NA-SCAD) continues to be poorly understood due to the rarity of this condition and its heterogeneous pathology. Although intimal tear or bleeding of vasa vasorum with intermedial hemorrhage seems to be the most probable reason, the exact underlying mechanism is still unknown.The exact etiology of spontaneous coronary artery dissection remains elusive; however, fibromuscular dysplasia and takotsubo cardiomyopathy have been considered as the potential cause of spontaneous coronary artery dissection. The underlying causes associated with SCAD include emotional stress, physical stress such as extreme valsalva maneuver, retching, vomiting, coughing, isometric exercise, history of using stimulant medications or illicit drugs, pregnancy, systemic lupus erythematosus, sarcoidosis, inflammatory bowel disease, celiac disease, vascular EhlersDanlos syndrome, Marfans syndrome, LoeysDietz syndrome. Spontaneous coronary artery dissection should be differentiated from other causes of acute coronary syndrome. Features suggestive of spontaneous coronary artery dissection include myocardial infarction in young women (age 50), absence of traditional cardiovascular risk factors, little or no evidence of coronary atherosclerosis, peripartum state, history of fibromuscular dysplasia, and history of connective tissue disorder or systemic inflammatory disorder.The annual incidence of spontaneous coronary artery dissection is estimated at 0.26 per 100,000 persons (0.33 in women and 0.18 in men), corresponding to approximately 800 new cases per year in the United States. The true prevalence of spontaneous coronary artery dissection in the general population remains unknown; however, retrospective angiographic registries have reported a SCAD detection rate of 0.1 to 1.1% among all coronary angiograms performed.The risk factors for spontaneous coronary artery dissection include predisposing factors ( vasculopathy, pregnancy, connective tissue disorder, systemic inflammation) and precipitating stressors (e.g., strenuous exercise, emotional stress, recreational drugs).Features that raise the index of suspicion for SCAD include myocardial infarction in young women (age 50), absence of traditional cardiovascular risk factors, little or no evidence of coronary atherosclerosis, peripartum state, history of fibromuscular dysplasia, history of connective tissue disorder or systemic inflammation.
SCAD usually is the result of an underlying vascular or connective tissue disorders. In order to provide the best care to patients with SCAD, the scientific statement from the American Heart Association  (AHA) recommended a detailed review of systems and personal and family history of SCAD-associated symptoms and conditions. In addition, AHA scientific statement recommended a complete vascular exam. Routine clinical or genetic screening of asymptomatic relatives of patients with SCAD is not recommended. However, genetic screening is recommended in first-degree family members of patients with SCAD in whom a monogenic vascular disease has been identified.The natural history of spontaneous coronary artery dissection has not been well characterized.  Early reports based on post-mortem examinations after sudden cardiac death suggest a dismal prognosis. However, recent studies demonstrate that most patients survive initial hospitalization and have a favorable prognosis following clinical stabilization.Coronary angiography is the standard for diagnosing spontaneous coronary artery dissection.  Adjunctive imaging modalities such as intravascular ultrasonography (IVUS), optical coherence tomography (OCT), computed tomography angiography (CTA), and magnetic resonance angiography (MRA) may offer complementary details for establishing a definitive diagnosis.The hallmark symptom of spontaneous coronary artery dissection (SCAD) is angina pectoris, similar to other acute coronary syndromes, which may radiate to the jaw or left arm. SCAD should be suspected with these symptoms in relatively young women, especially those in postpartum status. However, many patients do not have typical risk factors of coronary artery disease. Patients are typically asymptomatic on follow-up.Physical exam in SCAD may include tachycardia, bradycardia, hypertension, hypotension, rale, syncope based on the the coronary arteries involvement and ventricular dysfunction.Laboratory findings consistent with the diagnosis of spontaneous coronary artery dissection is similar to myocardial infarction as it most commonly presents with this manifestation. It includes elevated levels of troponin which may be absent in 27% of the patients.Electrocardiogram findings vary according to the coronary flow-limitation by the dissection flap or intramural hematoma. There can be no changes in ECG in some cases. In other cases ECG may show any of changes.The current gold standard for diagnosing spontaneous coronary artery dissection  (SCAD) is coronary angiography, as it is widely available and the first-line imaging modality for patients presenting with the acute coronary syndrome.  The predominant angiographic feature of SCAD consists of diffuse smooth narrowing of varying severity involving mid-to-distal coronary segments, secondary to compression of the true lumen and/or expansion of the false lumen by the development of an intramural hematoma. The typical appearance of extraluminal contrast staining, multiple radiolucent lumens, spiral dissection, or intraluminal filling defects is less commonly observed. Other angiographic findings associated with SCAD include coronary tortuosity, myocardial bridging, and coronary fibromuscular dysplasia.coronary computed tomography angiography maybe helpful in the diagnosis of spontaneous coronary artery dissection. Findings on coronary computed tomography angiography suggestive of spontaneous coronary artery dissection include abrupt luminal stenosis of the coronary lumen, intramural hematoma,tapered luminal stenosis, epicardial fat strand, coronary tortuosity, coronary bridging, myocardial hypoperfusion, regional wall motion abnormality.Cardiac magnetic resonance (CMR) is a valuable tool for diagnosis of spontaneose coronary artery dissection (SCAD) in patients as follows:
pregnant women for avoiding  radiation of coronary angiography, unclear evidence of acute coronary syndrome during coronary angiography, differentiating of SCAD from myocarditis, takotsubo cardiomyopathy. Findings of CMR associated with SCAD include evidence of myocardial infarction with subendocardial LGE,microvascular obstruction, myocardial edema.Echocardiography is helpful in the assessment of regional wall motion abnormalities, chamber size, and diastolic  function and monitoring of ventricular  recovery after SCAD. Contrast and strain echocardiography may be useful for evaluation of  underlying perfusion and myocardial dysfunction in SCAD.When the diagnosis of spontaneous coronary artery dissection (SCAD) cannot be ascertained by the standard coronary angiography, intracoronary imaging such as intravascular ultrasound (IVUS) or optical coherence tomography (OCT) may provide complementary information for establishing a definitive diagnosis.  Coronary computed tomography angiography (CCTA) may be useful for non-invasive follow-up of SCAD involving proximal or large-caliber coronary arteries. OCT findings suggestive of SCAD may include the presence of two lumens and intramural hematoma.Long-term treatment for spontaneous coronary artery dissection pursues several main goals including antianginal therapy, prevention of recurrence, assessment, and management of extra coronary vascular abnormalities, and improvement of quality of life. Acute management of myocardial infarction in SCAD is medical therapy in approximately 80% of the patients. Myocardial infarction in the context of SCAD is different from the myocardial infarction in the context of atherosclerosis and therefore makes it unfavorable for revascularization approaches.There are no specific guidelines regarding the optimal management of spontaneous coronary artery dissection. Based on the clinical and angiographic scenario, treatment options include conservative medical regimens similar to that for acute coronary syndrome, percutaneous coronary intervention, and/or coronary artery bypass surgery. In the majority of cases, SCAD may be managed successfully with medical treatment alone in the absence of ongoing myocardial ischemia or hemodynamic instability.
Initial conservative management typically includes antithrombotic therapy with heparin, aspirin, clopidogrel and glycoprotein IIb/IIIa inhibitors, and antiischemic therapy with beta blockers and nitrates.  However, the use of antithrombotic therapy may increase the risk of bleeding in the false lumen causing an expansion of the intramural hematoma, resulting in a decreased flow through the true lumen.Fibrinolytics should be avoided. Calcium channel blockers may offer relief in coronary artery spasm.Conservative management should be the first choice if emergent revascularization is not necessary. However, optimal management is in question due to insufficient clinical experience. There are some treatment options including conservative management, emergency revascularization (PCI or CABG), fibrinolytic therapy, mechanical hemodynamic support, and even cardiac transplantation have been reported.The preference of the approach should be tailored to the patients clinical status.Coronary artery bypass graft (CABG) is an important reperfusion therapy in a selected group of SCAD patients and also a rescue strategy in the management of failed PCI.Indications for surgical revascularization include multivessel involvement, Left main coronary artery involvement, progression/worsening of dissection, significant narrowing of the arterial lumen, refractory or recurrent myocardial ischemia. In the event of severe refractory heart failure, heart transplantation may be considered. There is no established primary prevention measurement for spontaneous coronary artery dissection.Secondary prevention strategies following spontaneous coronary artery dissection include avoidance of extreme isometric  or competitive physical exercise and also psychosocial support.Future studies are needed to further elucidate the underlying pathophysiology of this complex disorder as well as to gain a better understanding of the optimal treatment strategies and long-term outcomes of this unique patient population.

# Historical Perspective
Spontaneous coronary artery dissection (SCAD) was first described by Pretty in 1931 in which a 42-year-old woman presented with nausea and chest pain died unexpectedly due to rupture of a dissecting atheromatous aneurysm in the right coronary artery following repetitive retching and vomiting. In the post-morterm examination, heart muscle and valve appeared normal, and there was extensive hemorrhage between aorta and pulmonary artery secondary to coronary artery rupture presumably during the sudden and violent retching attack.

# Classification
Spontaneous coronary artery dissection can be classified based on angiographic appearance into type 1 (evident arterial wall stain with multiple radiolucent lumens), type 2 (diffuse smooth stenosis of varying severity), and type 3 lesions (focal or tubular stenosis mimicking atherosclerosis). Type 4 SCAD lesion is characterized by dissection leading to an abrupt total occlusion, usually of a distal coronary segment. The total occlusion occurs as a result of diminished true lumen due to external compression by intraluminal hematoma rather than embolism. The intermediate type 1/2 SCAD lesion is characterized by the appearance of type 1 in conjunction with type 2 lesion.

# Pathophysiology
At present, the pathophysiology of non-atherosclerotic spontaneous coronary artery dissection (NA-SCAD) continues to be poorly understood due to the rarity of this condition and its heterogeneous pathology. Although intimal tear or bleeding of vasa vasorum with intermedial hemorrhage seems to be the most probable reason, the exact underlying mechanism is still unknown. In a SCAD registry, a total of 5% to 8% of patients were carriers of genetic mutations for connective tissue disorders. SCAD may also be associated with a variety of disorders including but not limited to fibromuscular dysplasia, Connective tissue disorders, and autoimmune diseases such as systemic lupus erythematous.

# Causes
The exact etiology of spontaneous coronary artery dissection remains elusive; however, fibromuscular dysplasia and takotsubo cardiomyopathy have been considered as the potential cause of spontaneous coronary artery dissection. The underlying causes associated with SCAD include emotional stress, physical stress such as extreme valsalva maneuver, retching, vomiting, coughing, isometric exercise, history of using stimulant medications or illicit drugs, pregnancy, and connective tissue disorders.

# Differentiating Spontaneous Coronary Artery Dissection from Other Conditions
Spontaneous coronary artery dissection should be differentiated from other causes of acute coronary syndrome. Features suggestive of spontaneous coronary artery dissection include myocardial infarction in young women (age 50), absence of traditional cardiovascular risk factors, little or no evidence of coronary atherosclerosis, peripartum state, history of fibromuscular dysplasia, and history of connective tissue disorder or systemic inflammatory disorder.

# Epidemiology and Demographics
The annual incidence of spontaneous coronary artery dissection is estimated at 0.26 per 100,000 persons (0.33 in women and 0.18 in men), corresponding to approximately 800 new cases per year in the United States.  The true prevalence of spontaneous coronary artery dissection in the general population remains unknown; however, retrospective angiographic registries have reported a SCAD detection rate of 0.1% to 1.1% among all coronary angiograms performed. The case fatality rate of SCAD is relatively low compared with other causes of ACS, with an estimated in-hospital mortality rate of 0 to 4%. The average age at diagnosis of SCAD in females ranges from 44 to 53 years, although patients may present with SCAD in their second through ninth decades of life. SCAD has a strong predilection for young women with no or minimal traditional cardiovascular risk factors. It has been reported in all major racial and ethnic groups, with the majority of patients being white.

# Risk Factors
The risk factors for spontaneous coronary artery dissection include predisposing factors ( vasculopathy, pregnancy, connective tissue disorder, systemic inflammation) and precipitating stressors (e.g., strenuous exercise, emotional stress, recreational drugs).Features that raise the index of suspicion for SCAD include myocardial infarction in young women (age 50), absence of traditional cardiovascular risk factors, little or no evidence of coronary atherosclerosis, peripartum state, history of fibromuscular dysplasia, history of connective tissue disorder or systemic inflammation.

# Screening
SCAD usually is the result of an underlying vascular or connective tissue disorders. In order to provide the best care to patients with SCAD, the scientific statement from the American Heart Association (AHA) recommended a detailed review of systems and personal and family history of SCAD-associated symptoms and conditions. In addition, AHA scientific statement recommended a complete vascular exam. Routine clinical or genetic screening of asymptomatic relatives of patients with SCAD is not recommended. However, genetic screening is recommended in first-degree family members of patients with SCAD in whom a monogenic vascular disease has been identified.

# Natural History, Complications and Prognosis
The natural history of spontaneous coronary artery dissection has not been well characterized.  Early reports based on post-mortem examinations after sudden cardiac death suggest a dismal prognosis.  However, recent studies demonstrate that the majority of patients survive initial hospitalization and have a favorable prognosis following clinical stabilization. Some of the complications of SCAD include extension of dissection, recurrence of dissection, myocardial stunning, myocardial infarction, congestive heart failure, cardiogenic shock, ventricular arrhythmia, and sudden cardiac death.

# Diagnosis
Coronary angiography is the standard for diagnosing spontaneous coronary artery dissection.  Adjunctive imaging modalities such as intravascular ultrasonography (IVUS), optical coherence tomography (OCT), computed tomography angiography (CTA), and magnetic resonance angiography (MRA) may offer complementary details for establishing a definitive diagnosis.

## History and Symptoms
The hallmark symptom of spontaneous coronary artery dissection (SCAD) is angina pectoris, similar to other acute coronary syndromes, which may radiate to the jaw or left arm. SCAD should be suspected with these symptoms in relatively young women, especially those in postpartum status. However, many patients do not have typical risk factors of coronary artery disease. Patients are typically asymptomatic on follow-up.

## Physical Examination
Physical exam in SCAD may include tachycardia, bradycardia, hypertension, hypotension, rale, syncope based on the the coronary arteries involvement and presence of ventricular dysfunction.

## Laboratory Findings
Laboratory findings consistent with the diagnosis of spontaneous coronary artery dissection is similar to myocardial infarction as it most commonly presents with this manifestation. It includes elevated levels of troponin which may be absent in 27% of the patients.

## Electrocardiogram
Electrocardiogram findings vary according to the coronary flow-limitation by the dissection flap or intramural hematoma. There can be no changes in ECG in some cases. In other cases ECG may show any of changes.

## Angiography
The current gold standard for diagnosing spontaneous coronary artery dissection  (SCAD) is coronary angiography, as it is widely available and the first-line imaging modality for patients presenting with the acute coronary syndrome.  The predominant angiographic feature of SCAD consists of diffuse smooth narrowing of varying severity involving mid-to-distal coronary segments, secondary to compression of the true lumen and/or expansion of the false lumen by the development of an intramural hematoma.  The typical appearance of extraluminal contrast staining, multiple radiolucent lumens, spiral dissection, or intraluminal filling defects is less commonly observed.  Other angiographic findings associated with SCAD include coronary tortuosity, myocardial bridging, and coronary fibromuscular dysplasia.

## CT
coronary computed tomography angiography maybe helpful in the diagnosis of spontaneous coronary artery dissection. Findings on coronary computed tomography angiography suggestive of spontaneous coronary artery dissection include abrupt luminal stenosis of the coronary lumen, intramural hematoma,tapered luminal stenosis, epicardial fat strand, coronary tortuosity, coronary bridging, myocardial hypoperfusion, regional wall motion abnormality.

## MRI
Cardiac magnetic resonance (CMR) is a valuable tool for diagnosis of spontaneose coronary artery dissection (SCAD) in patients as follows:
pregnant women for avoiding  radiation of coronary angiography, unclear evidence of acute coronary syndrome during coronary angiography, differentiating of SCAD from myocarditis, takotsubo cardiomyopathy. Findings of CMR associated with SCAD include evidence of myocardial infarction with subendocardial late gadolinium enhancement, microvascular obstruction, myocardial edema.

## Echocardiography
Echocardiography is helpful in the assessment of regional wall motion abnormalities, chamber size, and diastolic  function and monitoring of ventricular  recovery after SCAD. Contrast and strain echocardiography may be useful for evaluation of  underlying perfusion and myocardial dysfunction in SCAD.

## Other Imaging Findings
When the diagnosis of spontaneous coronary artery dissection (SCAD) cannot be ascertained by the standard coronary angiography, intracoronary imaging such as intravascular ultrasound (IVUS) or optical coherence tomography (OCT) may provide complementary information for establishing a definitive diagnosis.  Coronary computed tomography angiography (CCTA) may be useful for non-invasive follow-up of SCAD involving proximal or large-caliber coronary arteries. OCT findings suggestive of SCAD may include the presence of two lumens and intramural hematoma.

## Other Diagnostic Studies

# Treatment
Acute management of myocardial infarction in SCAD is medical therapy in approximately 80% of the patients. Myocardial infarction in the context of SCAD is different from the myocardial infarction in the context of atherosclerosis and therefore makes it unfavorable for revascularization approaches. Long-term treatment for spontaneous coronary artery dissection pursues several main goals including antianginal therapy, prevention of recurrence, assessment, and management of extra coronary vascular abnormalities, and improvement of quality of life. To improve the qualityof life in patients with SCAD, consider cardiac rehabilitation referral and manage patients comorbidities.

## Medical Therapy
There are no specific guidelines regarding the optimal management of spontaneous coronary artery dissection. Based on the clinical and angiographic scenario, treatment options include conservative medical regimens similar to that for acute coronary syndrome, percutaneous coronary intervention, and/or coronary artery bypass surgery. In the majority of cases, SCAD may be managed successfully with medical treatment alone in the absence of ongoing myocardial ischemia or hemodynamic instability.
Initial conservative management typically includes antithrombotic therapy with heparin, aspirin, clopidogrel and glycoprotein IIb/IIIa inhibitors, and antiischemic therapy with beta blockers and nitrates.  However, the use of antithrombotic therapy may increase the risk of bleeding in the false lumen causing an expansion of the intramural hematoma, resulting in a decreased flow through the true lumen.Fibrinolytics should be avoided. Calcium channel blockers may offer relief in coronary artery spasm.

## Percutaneous Coronary Intervention
Conservative management should be the first choice if emergent revascularization is not necessary. However, optimal management is in question due to insufficient clinical experience. There are some treatment options including conservative management, emergency revascularization (PCI or CABG), fibrinolytic therapy, mechanical hemodynamic support, and even cardiac transplantation.The preference of the approach should be tailored to the patients clinical status.

## Surgery
Coronary artery bypass graft (CABG) is an important reperfusion therapy in a selected group of SCAD patients and also a rescue strategy in the management of failed PCI.Indications for surgical revascularization include multivessel involvement, Left main coronary artery involvement, progression/worsening of dissection , significant narrowing of the arterial lumen, refractory or recurrent myocardial ischemia. In the event of severe refractory heart failure, heart transplantation may be considered.

## Primary Prevention
There is no established primary prevention measurement for spontaneous coronary artery dissection.

## Secondary Prevention
Secondary prevention strategies following spontaneous coronary artery dissection include avoidance of extreme isometric or competitive physical exercise and also psychosocial support.

## Future or Investigational Therapies
Future studies are needed to further elucidate the underlying pathophysiology of this complex disorder as well as to gain a better understanding of the optimal treatment strategies and long-term outcomes of this unique patient population.