A 38-year-old woman arrived at the emergency department by private car complaining of substernal chest pain and nausea. Symptoms were relieved after administration of 2 sublingual nitroglycerin tablets. Electrocardiogram (ECG) demonstrated nonspecific T-wave changes, and initial troponin level was normal. Physical examination and chest x-ray were unremarkable. She was admitted for observation. Her second troponin level was elevated, and an echocardiogram showed anterior wall hypokinesis consistent with non–ST-segment elevation myocardial infarction (NSTEMI). She does not have diabetes, hypertension, or hyperlipidemia and has no family history of premature myocardial infarction. Coronary angiography showed narrowing in the left anterior descending coronary artery (Figure 19-1). Intravascular optical coherence tomography (OCT) confirmed intramural hematoma consistent with spontaneous coronary artery dissection (SCAD) (Figure 19-2). SCAD is nonatherosclerotic disruption and/or intramural hematoma of the coronary artery wall that can obstruct coronary blood flow and cause myocardial ischemia and/or infarct. Since the patient was pain free and hemodynamically stable, no intervention was performed. She was treated with baby aspirin, β-blockade, and low-dose nitrates. She had an uncomplicated hospital course and was dismissed after monitoring for 5 days.

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  Previously considered rare, SCAD is increasingly recognized as an important cause of acute coronary syndrome (ACS) and sudden cardiac death.

  
  
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  SCAD primarily occurs in younger people with few or no risk factors for coronary heart disease, in contrast to atherosclerotic myocardial infarction (MI).

  
  
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  It most commonly affects women (74%-92%) at mean age of 42 to 52 years.^1-4

  
  
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  It is the etiology of 10% to 20% of MIs in women <55 years old.^2,5,6

  
  
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  It is the most common cause of pregnancy-associated MI.⁷

  
  
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  As much as 18% of SCAD occurs during the peripartum period.¹

  
  
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  SCAD patients are commonly (25%-86%) found to have a systemic arteriopathy, most often fibromuscular dysplasia (FMD).^4,8-10

  
  
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  Survival is generally high among patients who survive to hospital admission.¹

  
  
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  Recurrent SCAD or MI is relatively common, and no secondary preventive measures have been identified.¹

The underlying causes and mechanisms of SCAD are uncertain. The female predominance suggests a sex-based or hormonal influence. It is likely that there is no single etiology for SCAD, and instead, the coronary arterial tear and/or intramural hematoma is a result of a combination of both a vulnerable patient and vulnerable coronary artery. Hypotheses for underlying mechanism include the following:

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  Systemic arteriopathies are common, as evidenced by a high prevalence of associated extracoronary vascular abnormalities, FMD (Figure 19-3),⁸ and coronary tortuosity (Figures 19-4 and 19-5).¹¹ Coronary artery involvement by these systemic processes may signal friability and risk of dissection.

  
  
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  Connective tissue disorders, such as Ehlers-Danlos syndrome type IV (vascular type) and Marfan syndrome and other monogenetic disorders have been associated with SCAD but represent a small fraction of patients with the condition.¹²

  
  
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  Hormonal fluctuations likely play a role, particularly in those with peripartum SCAD.¹

  
  
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  Catecholamine surges may be a trigger, as SCAD has been associated with recent extreme mental and physical stress.^1,13

  
  
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  Vascular shear stress or abnormal mechanical forces may contribute to SCAD that occurs in the setting of extreme physical exertion.^1,13

  
  
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  SCAD has been observed in family members, and there may be a genetic predisposition.¹⁴

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  SCAD typically presents with symptoms consistent with MI, unstable angina, or sudden death.^1,13

  
  
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  The onset of symptoms may be sudden, although some patients report stuttering discomfort or a prior finite episode of chest pain that resolved in the days leading up to their SCAD.¹⁵

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  When ACS is suspected, SCAD is typically confirmed via coronary angiography, with or without ancillary intracoronary imaging using intravascular ultrasound (IVUS) or OCT.

  
  
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  A high index of suspicion by the angiographer is important, as angiographic findings can be subtle or be easily misclassified. Younger patients, particularly women, those without risk factors or evidence of atherosclerosis in other vessels, or those who have a systemic arteriopathy or coronary artery tortuosity should be carefully evaluated for SCAD if an obvious cause of ACS is not identified on initial coronary imaging.

  
  
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  Three angiographic appearances of SCAD have been described: type 1, contrast staining in the arterial wall (Figure 19-6); type 2, diffuse narrowing (see Figure 19-1); and type 3, mimics atherosclerosis (Figure 19-7).¹⁶ Intimal disruption and/or intramural hematoma may be present in any of the subtypes.

  
  
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  Intravascular imaging such as OCT and IVUS may help visualize intramural hematoma and sometimes intimal disruption confirming SCAD in patients with type 2 (see Figures 19-1 and 19-2) and type 3 SCAD.¹⁷

  
  
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  SCAD may also be diagnosed on autopsy in the setting of sudden death or death before coronary angiography could be performed. Findings include intramural hematoma or flap and myocardial infarction in the corresponding coronary territory.^18,19 SCAD often occurs in the distal coronary artery and may be missed during postmortem evaluation.

  
  
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  Coronary computed tomography angiography may demonstrate coronary defects consistent with SCAD (Figure 19-8). However, because of the small caliber of certain coronary territories, the diagnosis may not always be obvious.