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.
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 should be admitted for 3-5 days to monitor for the early hazard of dissection extension or new recurrent SCAD.
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.
The coronary angiographic appearance of spontaneous coronary artery dissection has been classified into three types:
2.2% to 7.4% of patients require CABG after initial medical management or PCI. 
Female SCAD patients have a poorer prognosis, particularly postpartum patients were found to have larger infarcts, lower mean LV ejection fraction (34% vs. 49%; P<0.01), and proximal artery dissections. 
Spontaneous coronary artery dissection (SCAD) is a different clinical entity from acute coronary syndrome related to atherosclerotic disease. It is frequently seen in younger pre-menopausal women with risk factors including pregnancy and fibromuscular dysplasia.
Pregnancy-related SCAD has a worse clinical outcome. It is important to recognize that SCAD doesn’t affect premenopausal women alone with several reports demonstrating a mean age of 52.1±9.2 years, with 62.3% of the women being post-menopausal.
There should be a high index for clinical suspicion in younger women presenting with chest pain. It is infrequent, misdiagnosed, and underestimated diagnosis with significant consequences of ventricular arrhythmias, myocardial ischemia, and sudden cardiac death. 
Spontaneous coronary artery dissection mainly occurs in previously active patients but the risk can be exacerbated by strenuous exercise, particularly isometric exercises. Patients should not be arbitrarily advised to restrict physical activity and referral to a cardiac rehabilitation program should be strongly considered. Referral from Vancouver General Hospital SCAD Program (blood pressure no higher than 130/80 mm Hg; heart rate 50% to 70% of heart rate reserve; free weights for resistance training of 2 to 12 lb, starting low and gradually increasing can be considered. 
Patients face significant psychosocial stressors due to limited knowledge about the disease and lack of modifiable risk factors. Patient-centered counseling and support groups along with participation in organizations focusing on SCAD must be offered to these patients. 
Routine genetic testing for arteriopathies is not recommended in the absence of suggestive history or physical examination. Patients must be referred to a genetic counselor for formal assessment. Due to a higher incidence of extra coronary vascular abnormalities in patients presenting with SCAD and fibromuscular dysplasia, screening for aneurysms from the brain to pelvis should be considered. 
Spontaneous coronary artery dissection mainly occurs in a healthier and younger, fairly active patient population without the traditional cardiac risk factors. It does have a significant risk for recurrence. It is important to inform patients about warning signs like diaphoresis, shortness of breath, palpitations, chest pain and they should be advised to seek medical attention immediately. Prognosis depends on controlling underlying risk factors like hypertension, hyperlipidemia, and obesity. For patients who survive the initial presentation of SCAD, prognosis remains good. Patients should be advised to seek a close, long term clinical follow-up.
Recommendations regarding subsequent pregnancy in patients with SCAD are limited. Patients considering a subsequent pregnancy must be managed in tertiary cancer centers under the care of a multi-disciplinary team.
Due to a possible association with female sex hormones, hormonal contraception should be avoided with preferred contraceptive methods including vasectomy in the male partner, tubal ligation, and intrauterine devices with local delivery of progestin (levonorgestrel 20 μg/d). 
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.
Carotid artery dissection is a rare disorder that is best managed by an interprofessional team that includes a neurologist, radiologist, vascular surgeon, ICU nurses, and an internist. While the rare patient may require surgery, the majority of patients can be managed with medical therapy and endovascular stenting. 
The outlook for patients who have no neurological deficit at presentation is good. The patient must be informed on the need for better blood pressure control and elimination of risk factors for atherosclerosis.
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