INTRODUCTION — Spontaneous coronary artery dissection (SCAD) is a non-traumatic and non-iatrogenic separation of the coronary arterial wall and is an infrequent cause of acute myocardial infarction. It is more common in younger patients and in women. Modern usage of the term SCAD denotes nonatherosclerotic causes, which is the focus of this topic. Other aspects of coronary heart disease in women are discussed separately. (See "Clinical features and diagnosis of coronary heart disease in women".)
PATHOLOGY AND PATHOPHYSIOLOGY — The underlying mechanism of non-atherosclerotic SCAD is not fully understood, but an intimal tear or bleeding of vasa vasorum with intramedial hemorrhage has been proposed [1]. Both result in creation of a false lumen filled with intramural hematoma [2]. Pressure-driven expansion of the false lumen by an enlarging hematoma may lead to luminal encroachment and subsequent myocardial ischemia and infarction. Atherosclerotic cause of coronary dissection is a mechanistically distinct variant and is typically limited in extent by medial atrophy and scarring [3]. Non-atherosclerotic SCAD, on the other hand, can result in extensive dissection lengths, especially in the presence of arterial fragility from predisposing arteriopathies, and intracoronary imaging studies clearly show the absence of atherosclerosis in these cases [4,5].
In pregnant or early postpartum women, dissection may be a consequence of increased physiological hemodynamic stresses or from hormonal effects weakening the coronary arterial wall [6,7]. The exposure to recurrent and chronic hormonal pregnancy changes can further increase SCAD risks in women with multiple previous births (multiparity) [7]. (See "Acquired heart disease and pregnancy", section on 'Myocardial infarction' and 'Pregnancy and preconception counseling' below.)
Intramural hematoma involving the outer two-thirds of the media is common. Histologically, an inflammatory reaction (eg, eosinophilic infiltrates) in the adventitia has been described, suggestive of periarteritis that may breakdown the medial-adventitial layer predisposing the artery to dissection. However, this inflammatory response may be reactive rather than causative [6].
One retrospective study has proposed that coronary artery tortuosity may be a marker for or a potential mechanism for SCAD [8]. In this study, the coronary angiograms of 246 patients with SCAD were compared with 313 controls. Tortuosity, as defined by the presence of ≥3 consecutive curvatures of 90 to 180 degrees measured at end-diastole in a major epicardial coronary artery ≥2 mm in diameter, was found in 78 and 17 percent, respectively. However, the presence of coronary tortuosity was also associated with extracoronary vasculopathy (eg, fibromuscular dysplasia) [9,10]; as such, it is more likely that the tortuosity, similar to dissection, is a manifestation of the underlying predisposing vasculopathy.
DISEASE ASSOCIATIONS AND CAUSES — In most cases, a predisposing arterial disease association or cause is identified [11]. However, up to 20 percent of cases are labeled as idiopathic [12]. Most patients presenting with this entity typically do not have conventional risk factors for coronary heart disease [12,13].
Potential predisposing factors include fibromuscular dysplasia (FMD), postpartum status, multiparity (≥4 births), connective tissue disorders, systemic inflammatory conditions, and hormonal therapy [12-16]. (See "Clinical manifestations and diagnosis of fibromuscular dysplasia".)
In a study of 168 patients with SCAD, one or more of these was found in about 80 percent [12]. In this study, which screened all patients with invasive or noninvasive angiography of the cerebral, iliac, or renal circulations, FMD was diagnosed in 72 percent in one or more territories. Other studies have also found a high percent of patients have extracoronary vascular abnormalities, including fibromuscular dysplasia, dissection, tortuosity, and aneurysms [8]. In contrast, association with systemic inflammatory conditions appeared to account for a small proportion of cases [12,13].
In a small proportion of cases (about 5 percent), SCAD can be associated with connective tissue diseases such as Marfan or vascular Ehlers-Danlos syndrome, where medial degeneration has been proposed to weaken the arterial wall and predispose to spontaneous dissections [16-18]. (See "Clinical manifestations and diagnosis of Ehlers-Danlos syndromes".)
Although case reports have raised the possibility that autoimmune disease is involved in the etiology of SCAD, a 2020 case (114)-control (342) study found no association [19].
Evidence for one or more causal genes also exists, and these can increase the risk of SCAD [20-22].
In over 50 percent of SCAD cases, there are identifiable cardiocirculatory stressors that may increase the risk of acute SCAD events; this is especially true if there is preexisting arteriopathy such as fibromuscular dysplasia. [12,16]. These stressors include intense exercise (24.4 to 28.1 percent) with heavy isometric activities in half of these, emotional stress (40.5 to 48.3 percent), labor and delivery (2.4 percent), recreational drug use, and high-dose hormonal therapy (10.7 percent).
EPIDEMIOLOGY — In the general population, SCAD is the cause of acute coronary syndrome (ACS) in 0.1 to 4 percent of cases [23-26]. In a 2018 report of an administrative database (National Impatient Sample) of data from over 13 million patients who presented with an ACS between 2005 and 2015, the incidence of SCAD was reported at 0.49 percent [27]. In another analysis from the same database, SCAD was reported in 0.98 percent of approximately 750,000 women who presented with a myocardial infarction who underwent coronary angiography from 2009 to 2014 [28]. However, these estimates likely under reported the true incidence of SCAD, as this disease was underdiagnosed and misdiagnosed, especially in that early era.
SCAD has been reported to account for nearly a quarter of cases of ACS in women ≤50 years old [29]. In two studies of 87 and 168 patients, the mean age was 43 and 52 years and 82 and 92 percent were women, respectively [12,13]. Although classically thought to affect young women, SCAD is now increasingly recognized to also occur in older and postmenopausal women. In a 327-patient cohort, 22 percent were over age 60, and 57 percent of women affected were postmenopausal [16]. In the largest multicenter prospective SCAD registry to date (the Canadian SCAD Cohort Study), the mean age of the 750 SCAD patients was 51.8 years, with 9.2 percent older than age 65, and 88.5 percent were women [30]. Men can also present with SCAD (<10 to 15 percent of cases); however, mechanistically, these are more likely atherosclerotic in origin than non-atherosclerotic [31]. Men were slightly younger (mean age 48.6 versus 52.3 years in women), and were more likely to have isometric exertion as a stressor than women [32].
CLINICAL MANIFESTATIONS — Patients with non-atherosclerotic SCAD usually present with symptoms and signs characteristic of acute myocardial infarction (MI). Chest pain was the most common symptom presentation in 96 percent of cases; less common symptoms include arm pain, neck pain, nausea or vomiting, diaphoresis, dyspnea, and back pain [13,23,33]. (See "Initial evaluation and management of suspected acute coronary syndrome (myocardial infarction, unstable angina) in the emergency department", section on 'Clinical presentation' and "Initial evaluation and management of suspected acute coronary syndrome (myocardial infarction, unstable angina) in the emergency department", section on 'Physical examination'.)
Other important clinical triggers and manifestations of SCAD include:
●Intense exertion preceded the event in 28.9 percent of cases, including isometric stress lifting/pushing >50 pounds in 9.8 percent of cases. Emotional stress preceded the event in approximately 50 percent of cases [12,30].
●Postpartum status was reported in 2 to 18 percent of cases [12,13,30].
●ST-elevation MI (STEMI) was present in 25 to 50 percent of patients, with the remainder presenting with non-ST-elevation MI [12]. Very rarely (<1 percent of cases), there can be no troponin elevation [30].
●Life-threatening ventricular arrhythmias occurred in 4 to 14 percent [12,13,30].
●Cardiogenic shock was reported in 2 to 19 percent of patients with SCAD, depending on the proportion of patients with STEMI [26].
At the time of coronary angiography, the following findings were noted:
●The left anterior descending coronary artery was the most frequently affected vessel (approximately 40 to 70 percent of cases) [12,13,30]. The left main coronary artery was involved in 13 percent in one series that included only STEMI SCAD patients [26], with other series showing much lower incidence of left main coronary artery involvement (approximately 2 percent).
●The most commonly observed angiographic type was 2 (60 to 67 percent) [12]. (See 'Diagnosis' below.)
●Most patients had only one coronary artery involved (approximately 87 percent), but multivessel involvement of non-contiguous coronary segments was not infrequent [30,34].
These findings are generally consistent with earlier reports [6,35-37]. However, many earlier series included patients with associated significant atherosclerotic coronary artery disease, which could potentially influence epidemiology, clinical presentation, or prognosis.
SCAD patients may simultaneously present with dissections in other vascular beds, such as the carotid or vertebral arteries [34]. This highlights that a subset of patients may have a systemic predisposing arteriopathy compounded by an intense systemic precipitating milieu (be it hormonal, inflammatory, emotional, or physical), which may complicate their presenting symptoms.
DIAGNOSIS — Spontaneous coronary artery dissection (SCAD) should be considered in any young patient, especially a woman, without a history of coronary heart disease or risk factors, who presents with an acute myocardial infarction or cardiac arrest. (See "Initial evaluation and management of suspected acute coronary syndrome (myocardial infarction, unstable angina) in the emergency department", section on 'Clinical presentation' and "Initial evaluation and management of suspected acute coronary syndrome (myocardial infarction, unstable angina) in the emergency department", section on 'Physical examination' and "Overview of sudden cardiac arrest and sudden cardiac death".)
In the absence of prior trauma, the diagnosis of SCAD is made in most patients at the time of coronary angiography. Criteria for the angiographic definition include the presence of a non-iatrogenic dissection plane in the absence of coronary atherosclerosis, with typical changes of radiolucent intimal flap and contrast staining. However, a contemporary angiographic series has shown that such stereotypical changes were seen in only <30 percent of non-atherosclerotic SCAD cases [12,16]. The majority of SCAD had long and diffuse narrowing on angiography due to intramural hematoma, and this appearance was frequently unrecognized on angiography leading to under-diagnosis of this condition.
The coronary angiographic appearance of SCAD has been classified into three types (image 1A-C) [38]:
●Type 1: Pathognomonic contrast dye staining of arterial wall with multiple radiolucent lumen, with or without the presence of dye hang-up or slow contrast clearing [13].
●Type 2: Diffuse long and smooth stenosis that can vary in severity from mild stenosis to complete occlusion
●Type 3: Mimics atherosclerosis with focal or tubular stenosis and requiring optical coherence tomography (OCT) or intravascular ultrasound (IVUS) to differentiate the cause.
In patients for whom the diagnosis is considered but not secured with coronary angiography, intracoronary imaging with OCT or IVUS may be helpful. With these imaging modalities, SCAD diagnosis is made with the presence of intramural hematoma and/or a double lumen. Alternatively, repeat coronary angiography may be pursued four to six weeks later to evaluate for spontaneous angiographic healing of the dissected segment, if the diagnosis is uncertain. (See "Intravascular ultrasound, optical coherence tomography, and angioscopy of coronary circulation".)
Some studies have suggested roles for cardiac computed tomography (CT) angiography [39,40] and cardiac magnetic imaging in patients with suspected SCAD [41]. However, a substantial proportion of acute SCAD cases can be missed on CT angiography, and therefore this imaging modality should not be used as first-line imaging to diagnose SCAD. Cardiac MRI can be useful to differentiate SCAD from other causes of nonischemic myocardial injury, such as Takotsubo syndrome or myocarditis [42]. (See "Clinical utility of cardiovascular magnetic resonance imaging", section on 'Ischemic heart disease'.)
MANAGEMENT — In most SCAD patients, conservative therapy is the preferred strategy after the diagnosis is secured [10,25,43]. However, the optimal management is uncertain, in part due to the limited clinical experience. A wide range of approaches, including conservative management, emergency revascularization with percutaneous coronary intervention (PCI) or coronary artery bypass grafting (CABG), fibrinolytic therapy (with or without subsequent PCI), mechanical hemodynamic support, and cardiac transplantation have been reported [12,29,31,44].
Patients presenting with acute myocardial infarction who have symptoms of ongoing ischemia or hemodynamic compromise should be considered for revascularization with PCI or coronary artery bypass grafting [12,25]. Revascularization in patients with SCAD is technically challenging and associated with higher failure rates or complications [12,13,43,45]. A 53-patient SCAD-STEMI series from two centers reported a 91 percent success rate with emergent PCI; however, the definition of success differed from other series [26]. The largest SCAD series to date of 750 patients reported a PCI success/partial success rate of 69.9 percent among 106 SCAD patients who underwent PCI [30].
Until further evidence is available to guide therapy, a conservative approach is recommended unless there is ongoing ischemia, hemodynamic instability, or left main dissection. Angiographic "healing" of SCAD lesions has commonly been observed after conservative management [25].
Many patients have been managed with long-term aspirin, beta blocker, and short-term clopidogrel, with the addition of a statin in patients with dyslipidemia [12,46]. The use of beta blocker was associated with lower risk of recurrent SCAD (hazard ratio 0.36, p = 0.004) in multivariable analysis in the large 327-patient cohort [16]. Ongoing prospective studies on SCAD should further elucidate the medical management of this challenging and relatively unexplored condition (NCT02188069 and NCT02008786).
PCI with SCAD is often technically challenging in part due to fragility of the vessel wall. Advancing coronary guidewires within the true lumen can be challenging. Any instrumentation (wiring, angioplasty, or stenting) can propagate dissection and occlude side branches. In addition, dissections often affect small caliber distal vessels and are extensive, requiring long stents with high likelihood of subsequent in-stent restenosis. Furthermore, temporal resolution of intramural hematoma in previously stented segments may increase the risk of late stent mal-apposition and stent thrombosis. Thus, PCI should only be pursued when there is a strong clinical indication, and consideration should be given to utilizing adjunctive intracoronary imaging to optimize stent strut apposition. The use of bioabsorbable stents may have theoretical advantages [7]. The use of cutting balloon to fenestrate the false lumen to decrease burden of intramural hematoma compression of true lumen may also have utility [47].
Activities after spontaneous coronary artery dissection — Patients are encouraged to join cardiac a rehabilitation program after discharge. Although there are a few differences in exercise recommendations after SCAD from standard myocardial infarction patients, a SCAD-specific rehabilitation program is recommended if available [48]. This program encompasses a multidisciplinary approach including exercise rehabilitation, psychosocial counselling, dietary and cardiovascular disease education, and peer group support. To reduce arterial shear stress, target exercise heart rate is recommended at 50 to 70 percent of heart rate reserve, and systolic blood pressure during exercise is limited to <130 mmHg. Exercise is adjusted to upper heart rate target to achieve rating of perceived exertion of "moderate" to "somewhat difficult." Women are instructed to avoid lifting weights >20 to 30 pounds, and men to avoid >50 pounds. Such a program was shown to be safe and beneficial in a cohort of 70 SCAD patients, with improvement in chest pains, exercise capacity, psychosocial well-being, and cardiovascular events.
PROGNOSIS — Information regarding the prognosis of patients with spontaneous coronary artery dissection (SCAD) are derived from a few series in which management varied. Prognosis for SCAD in pregnancy is discussed below. (See 'Pregnancy and preconception counseling' below.)
In a population-based national administrative database from 2004 to 2015, 66,360 patients were reported to have SCAD, and the in-hospital mortality was 4.2 percent [27]. In the 750-patient prospectively enrolled SCAD study from 22 centers in North America (Canadian SCAD Cohort Study), in-hospital major adverse event rate was 8.8 percent, which included mortality (0.1 percent), recurrent MI (4.0 percent), cardiogenic shock (2.0 percent), and unplanned revascularization (2.5 percent). In a cohort of 327 patients who were followed prospectively (median follow-up 3.1 years) and in which an initial conservative approach was applied in 83 percent, the following was noted [12,16]:
●The recurrent in-hospital MI rate was 4.6 percent, with unplanned revascularization in 4.3 percent.
●Long-term major adverse coronary events were common (median 3.1 years): recurrent MI 16.8 percent (recurrent SCAD 10.4 percent).
The in-hospital prognosis was generally good for those managed either conservatively or with coronary artery bypass grafting, while the short-term outcome appeared less favorable for those managed with percutaneous coronary intervention (PCI) [12,13,43]. Acute PCI success was observed in less than 50 to 70 percent of cases [12,30,43], and long-term success without complication was observed in 30 percent only [12]. Overall, the two-year major adverse event rate was 10 to 17 percent, with observed recurrent dissection rate of 13 percent.
In a retrospective 87-patient series, the estimated 10-year rate of death, heart failure, myocardial infarction, or dissection recurrence was 47 percent (median follow-up of 47 months) [13]. Their observed recurrent SCAD rate was 17 percent. The same group also observed that coronary tortuosity may be associated with a higher risk of recurrent SCAD [8].
Overall, recurrent cardiovascular events appear frequently following an initial SCAD event, and repeat coronary dissection may occur in 13 to 17 percent with long-term follow-up. Further prospective and ongoing SCAD studies (Canadian SCAD Cohort Study [NCT02188069] and the "Virtual" Mayo Clinic SCAD Registry [NCT01429727]) will help elucidate the long-term cardiovascular outcome of this condition.
PREGNANCY AND PRECONCEPTION COUNSELING — In patients who had prior SCAD who are considering getting pregnant or who are already pregnant, the timing, features, and prognosis of pregnancy-associated SCAD are important to discuss. When discussing pregnancy with patients with a history of SCAD, we emphasize potential risks, and if they choose to get pregnant, patients will need high-risk pregnancy care.
●Pregnancy-associated SCAD – This most often presents early postpartum and is associated with a more severe presentation compared with SCAD not associated with pregnancy. In a single-center registry including 54 females with pregnancy-associated SCAD, four people presented during pregnancy (7.4 percent), 48 within 12 weeks following delivery (89 percent), one following a first trimester miscarriage (2 percent), and one following a stillbirth at 36 weeks (2 percent) [49]. These findings were similar to a study from Kaiser Permanente Northern California in which 18 of 22 females with pregnancy-associated SCAD presented postpartum (81 percent) [50]. In both studies, the majority of patients presenting with SCAD postpartum did so within the first month post-delivery (70 to 83 percent) [49,50].
Although no patients died from pregnancy-associated SCAD in either registry, both studies showed that people who had SCAD during pregnancy had more severe presentations compared with those who had SCAD that was not related to pregnancy [49,50]. Patients with pregnancy-associated SCAD had more proximal and multivessel coronary artery dissections, more heart failure, and lower average left ventricular ejection fraction on presentation compared with patients with SCAD not associated with a pregnancy. A separate study analyzed 13 patients who had died from pregnancy-associated SCAD from the MBRRACE-UK registry [51]. Among these deaths, three occurred during pregnancy, and 10 occurred postpartum (median 16 days postpartum [range 10 to 94]). Twelve patients had an out-of-hospital cardiac arrest; three underwent angiography, including one female who was alive at presentation to the hospital and two females who had angiography during active resuscitation. None underwent revascularization. Females who did not have angiography had autopsy-confirmed SCAD.
●Recurrence of SCAD with pregnancy – In people with SCAD (whether pregnancy related or not), there is a risk of recurrence during pregnancy or the postpartum period. Data from multiple SCAD registries were combined to evaluate 82 patients with pregnancy-associated SCAD [51], including the 13 from the previously mentioned United Kingdom registry who died. This study showed that SCAD occurred predominantly during six months postpartum, with only a few cases presenting during pregnancy. In the subset of 28 patients who had 37 pregnancies after their initial SCAD diagnosis, the following observations were reported:
•Conception after the most recent SCAD event occurred after a median of 30 months.
•Three women opted for medical termination (because of medical advice received about the risk of pregnancy), and seven spontaneous miscarriages occurred in three patients.
•Three pregnancy-associated major adverse cardiovascular and cerebrovascular events occurred. One was recurrent acute myocardial infarction at 19 weeks of gestation (this was thought to be recurrent SCAD and was managed without invasive angiography); the other two were angiographically confirmed recurrent SCAD events occurring within 12 months of delivery.
•No maternal or neonatal deaths were reported among those with prior SCAD who became pregnant.
FURTHER EVALUATION — Since a significant proportion of patients with SCAD have associated extracoronary fibromuscular dysplasia (see 'Disease associations and causes' above), experts recommend a full-body cross-sectional imaging (preferably with computed tomographic angiography) to diagnose concomitant fibromuscular dysplasia [25,52,53]. (See "Clinical manifestations and diagnosis of fibromuscular dysplasia".)
SOCIETY GUIDELINE LINKS — Links to society and government-sponsored guidelines from selected countries and regions around the world are provided separately. (See "Society guideline links: Non-ST-elevation acute coronary syndromes (non-ST-elevation myocardial infarction)" and "Society guideline links: ST-elevation myocardial infarction (STEMI)".)
SUMMARY AND RECOMMENDATIONS
●Definition – Spontaneous coronary artery dissection (SCAD) is defined as a non-traumatic and non-iatrogenic separation of the coronary arterial wall. (See 'Introduction' above.)
●Clinical manifestations – While uncommon, SCAD should be considered in any young patient, especially young women, without a history of coronary heart disease or risk factors, who presents with an acute myocardial infarction or cardiac arrest. (See 'Clinical manifestations' above.)
●Diagnosis – The diagnosis is made at the time of urgent coronary angiography. (See 'Diagnosis' above.)
●Management – Despite data suggesting good clinical outcomes with revascularization, conservative therapy, rather than revascularization, is the preferred strategy for most patients. Many patients should be considered for long-term aspirin and beta blocker. (See 'Management' above.)
●Prognosis – There is a high rate of recurrent events. (See 'Prognosis' above.)
●Pregnancy and preconception counseling
•In patients with existing SCAD who are considering getting pregnant or who are pregnant, the timing, features, and prognosis of pregnancy-associated SCAD are important to discuss. (See 'Pregnancy and preconception counseling' above.)
•Pregnancy-associated SCAD is most likely to occur in the first month postpartum. Although pregnancy-related SCAD has a more severe presentation than non-pregnancy-related SCAD, the occurrence of death is rare. Most pregnancy-associated SCAD deaths occur postpartum and as a result of an arrhythmia.
•Among females with a diagnosis of SCAD, there is a risk of recurrence during pregnancy or the postpartum period. If pregnancy is desired or takes place, referral to a team of providers (including a cardiologist) who manage high-risk pregnancies is recommended.
ACKNOWLEDGMENT — The UpToDate editorial staff thank Pamela S. Douglas, MD, for her past contributions as an author to prior versions of this topic review.
