Spontaneous coronary artery dissection (SCAD) is a rare, nontraumatic, and noniatrogenic shearing of the coronary arterial wall, which creates a false lumen and can result in acute myocardial infarction. Separation can occur between either the intima and media or the media and adventitia of the arterial wall, resulting in an intramural hematoma, which can occlude or impair coronary blood flow and result in myocardial ischemia or infarction (acute coronary syndrome [ACS]).

While considered a rare condition, the true incidence of SCAD is difficult to assess as it is an underdiagnosed condition with a majority of the data about the condition drawn from postmortem examinations. Among patients presenting for medical care with ACS, approximately 3%-4% have been found to have SCAD, while 0.3% of those presenting for routine coronary angiography are found to have the condition. Young women (younger than 50 years) have a higher prevalence of approximately 8.7%, rising to 10.8% in the subgroup of women presenting with ST-elevation myocardial infarction. SCAD has been reported to account for almost 25% of ACS cases in women younger than 50 years, although more recent data in some single center studies indicate these measurements may significantly underestimate the prevalence of this condition, with high rates of missed or delayed diagnoses.

SCAD may occur due to the development of an intimal tear or secondary to an intraluminal hemorrhage. Predisposing arterial conditions include fibromuscular dysplasia, pregnancy, connective tissue disorders (eg, Marfan syndrome, Ehlers-Danlos syndrome), systemic inflammatory conditions (eg, systemic lupus erythematosus, Crohn disease, polyarteritis nodosa, sarcoidosis), use of hormonal therapy, and history of coronary artery spasm. It was previously believed that most cases of SCAD were idiopathic, but more recent studies employing appropriate screening for predisposing arteriopathies have found that the percentage of SCAD cases considered idiopathic is much lower than previously reported. Similarly, while the hormonal and cardiovascular changes associated with pregnancy and labor are thought to increase the risk of SCAD, recent studies have found the percentage of SCAD cases that are peripartum is less than the 30% quoted in older literature (as low as 2.4% in some series). Other stressors that can precipitate SCAD, aside from labor, include intense exercise, Valsalva-style straining, vomiting, retching, emotional stress, and use of stimulants or illicit drugs.

Recent studies have demonstrated that the mortality rates associated with SCAD are much lower than originally reported, with modern estimates of mortality rates of 0%-7% and long-term mortality rates for SCAD lower than rates for standard ACS.