Coronary artery dissection can be spontaneous, traumatic, or due to iatrogenic causes. This review will focus on spontaneous coronary artery dissection (SCAD). Spontaneous coronary artery dissection is the non-traumatic and non-iatrogenic separation of the coronary arterial wall. It is an uncommon cause of acute myocardial infarction. It affects young to middle-aged women with men accounting for less than 10% to 15% of cases in most large contemporary series. Although historically it was thought to be rare, the increased use of early angiography to assess acute chest pain presentations has resulted in recognition of spontaneous coronary artery dissection as more common. The condition poses diagnostic challenges and significant therapeutic dilemmas given the lack of research to guide management.
In most cases, a predisposing arterial disease association or cause is identified. However, up to 20% cases are labeled as idiopathic.
Most patients who are at low-risk for the conventional atherosclerotic disease are underdiagnosed and possibly have lower rates of presentation; therefore, the true incidence of spontaneous coronary artery dissection is unknown. In the general population, spontaneous coronary artery dissection is the cause of acute coronary syndrome (ACS) in 0.1% to 0.4% cases. It mainly affects young females, and it has been reported to account for nearly a quarter of ACS cases in women younger than 50 years old. Spontaneous coronary artery dissection is also increasingly reported to occur in older and postmenopausal women. Less than 10% to 15% cases occur in men.
Non-atherosclerotic spontaneous coronary artery dissection arises from a tear in the tunica intima of the blood vessel, with blood entering and separating the layers of the arterial wall. A false lumen is eventually created in the medial layer which is filled with intramural hematoma. The increasing pressure of the false lumen by an enlarging hematoma causes external compression of the true coronary lumen resulting in restricted coronary blood flow and eventually leading to coronary insufficiency. This should be differentiated from atherosclerotic dissections, which result from plaque rupture or erosions allowing blood to enter the intimal space and from iatrogenic dissections that occur during coronary procedures.
Patients with spontaneous coronary artery dissection usually present with symptoms and signs characteristic of acute myocardial infarction (MI). Chest or shoulder pain, syncope, dyspnea, diaphoresis, and nausea associated with elevation of cardiac enzymes are the most common presentation. A small proportion (3% to 14%) of patients present with resuscitated ventricular arrhythmias. Some cases present as sudden unexplained death, although, because of the challenges of accurate post-mortem diagnosis, this condition is under-represented in most cases.
A high index of clinical suspicion is required for women presenting with typical chest pain and ECG or cardiac biomarker abnormalities.
Most patients present with elevated troponins, but there are no blood biomarkers currently available which distinguish spontaneous coronary artery dissection from other causes of ACS.
The diagnosis of spontaneous coronary artery dissection in most patients is made at the time of coronary angiography. In patients for whom the diagnosis is not secured with coronary angiography, intracoronary imaging with optical coherence tomography (OCT) or intravascular ultrasound (IVUS) may be helpful.
The coronary angiographic appearance of spontaneous coronary artery dissection has been classified into three types:
While spontaneous coronary artery dissection has been reported in all coronary segments, it has a frequent predilection for distal coronary segments. When proximal segments are involved, they more commonly have a type 1 appearance, and distal segments usually have a type 2 appearance. Left anterior descending artery is identified to be the most commonly affected vessel in majority studies.
Spontaneous coronary artery dissection poses major therapeutic challenges given limited evidence to guide management. Therefore, the choice of medical treatment, percutaneous coronary intervention (PCI), coronary artery bypass grafting (CABG), fibrinolytic therapy, mechanical hemodynamic support and heart transplantation is largely dictated by the clinical presentation and the degree of compromise to coronary flow on the angiographic study. Conservative therapy, rather than revascularization, is the preferred strategy for most patients.
Patients presenting with acute myocardial infarction who have symptoms of ongoing ischemia or hemodynamic compromise should be considered for revascularization with PCI or CABG. However, revascularization in patients with spontaneous coronary artery dissection is technically challenging and associated with higher failure rates or complications. Until further evidence is available to guide therapy, a conservative approach is recommended in patients with non-critical luminal obstruction, normal TIMI grade 3 flow, and a stable clinical situation.
Fibrinolytic therapy in spontaneous coronary artery dissection is avoided because of risks of dissection, expansion, or even rupture leading to cardiac tamponade.
There are currently no clinical trials to guide optimal medical management following spontaneous coronary artery dissection. Patients should be considered for long-term aspirin and beta-blocker therapy. Dual antiplatelet therapy followed by antiplatelet monotherapy is usually indicated in patients who have undergone PCI with stenting for spontaneous coronary artery dissection. The indication is unclear in patients without stents. Anticoagulant therapy is not recommended due to the risks of dissection extension/expansion.
Statin therapy should be considered for patients with dyslipidemia. In patients with left ventricular systolic dysfunction following spontaneous coronary artery dissection, the addition of angiotensin-converting enzyme inhibitors (ACEi), angiotensin receptor antagonists (ARB), and aldosterone antagonists are recommended.
Implantable Cardioverter-Defibrillator (ICD)/Mechanical Left Ventricular Assist Devices (LVAD)/Heart Transplantation
Extreme cases of significant myocardial injury, hemodynamic instability, and cardiogenic shock may require LVAD as a bridge to transplantation. ICD placement should be considered for secondary prevention in patients with severe left ventricular function impairment.
Risk of Recurrence
The rate of recurrence ranges from 5% to 19% of cases. Recurrent events may occur in the same or different artery. Many patients continue to experience significant chest pain after healing of the primary lesion.
Contraception after spontaneous coronary artery dissection
Due to the role of sex hormones in the pathogenesis of spontaneous coronary artery dissection, the use of hormonal contraceptives in women post-spontaneous coronary artery dissection is controversial. Barrier contraceptives and hormone free intra-uterine contraceptives may be used.