Spontaneous coronary artery dissection: Principles of management

Coronary angiography

As with ACS caused by disruption of atherosclerotic plaque, SCAD is most commonly diagnosed during coronary angiography. However, unlike in plaque rupture, the angiographic appearance of a dissected coronary artery includes multiple radiolucent lines, contrast staining with delayed clearance, and diffuse long narrowing without evidence of significant atherosclerosis apparent in other coronary arteries.¹⁰ Coronary angiography is regarded as the gold standard to confirm the presence of SCAD, but if not definitive, an adjunctive technique such as intravascular ultrasonography¹¹ or optical coherence tomography may be used, with the choice usually based on availability and local expertise.

Optical coherence tomography is particularly useful as it has high spatial resolution (< 10 μm), facilitating detection of true and false lumens, intramural hematoma, and entry tears.¹² However, it requires additional strong contrast injections and faster pullback speeds that could theoretically extend the dissection plane.

Intravascular ultrasonography is more familiar and more widely available than optical coherence tomography.

Coronary computed tomography angiography is an attractive option due to its ability to demonstrate dissection flaps and intramural hematomas. However, false-negative results are common.¹³ Coronary arterial defects may be subtle, and the distal vessels (often affected by SCAD) are poorly visualized. Current technology has a potential role in evaluating recurrent symptoms or in follow-up, but it has not yet demonstrated adequate sensitivity to rule out SCAD in the acute setting.¹⁴

Data supports a conservative approach

Observational studies have consistently demonstrated that PCI in the setting of SCAD is associated with worse outcomes and high complication rates.¹⁷

In a retrospective study of 189 patients with SCAD, the procedural failure rate was 53% in those managed with PCI.¹⁸ Reasons for technical failure included wire entry into a false lumen, final loss of flow after stent placement, and significant residual stenosis. In addition to procedural failure, PCI was associated with a high risk for emergency coronary artery bypass grafting (CABG), ie, 13% vs 2% in the medically managed group. These data are consistent with other observational studies citing high PCI failure rates. In a large Vancouver cohort of 327 patients with SCAD, 54 were treated with PCI; only 43.1% of procedures were deemed successful.⁴ In a smaller study of 134 patients with SCAD in Italy, the procedure success rate was reported at 72.5%, with a trend toward higher incidence of major adverse cardiovascular events in the invasive group, driven by a higher rate of repeat revascularization.¹⁹

Revascularization appropriate in some cases

Despite these often poor outcomes, revascularization procedures may be appropriate in patients with the following high-risk features:

• Left main coronary artery dissection

• Ongoing ischemia

• Thrombolysis in Myocardial Infarction (TIMI) grade 0–1 flow in a proximal vessel

• Hemodynamic instability

• Refractory arrhythmia.^10,20,21 The goals of PCI are somewhat different for SCAD than for traditional ACS. The goal of PCI in atherosclerotic ACS is to restore flow to TIMI grade 3, with residual stenosis of 20% or less. The goal in SCAD is to improve baseline TIMI flow by at least 1 grade or to maintain or achieve TIMI grade 2 or 3, and to reduce residual stenosis to less than 50%.²²

However, neither PCI with intracoronary stenting nor CABG appears to be protective against recurrent dissection.^18,19 A study that included 20 patients who underwent CABG for SCAD found that at 5 years, 1 patient had recurrent SCAD, 3 had heart failure, and 6 had target-vessel revascularization, presumably secondary to healing of native coronary arteries resulting in competitive flow.¹⁸

Mechanical support for shock

For SCAD complicated by cardiogenic shock, mechanical circulatory support may be considered in accordance with consensus guidelines for non-SCAD ACS treatment.²³ While case reports suggest that an intraaortic balloon pump and extracorporeal membrane oxygenation can be used safely in patients with SCAD,^24,25 they should be used with caution because, given the high incidence of concomitant arteriopathies in patients with SCAD, insertion of large-bore arterial catheters can theoretically result in iatrogenic dissection of the iliac arteries or aorta.

Antiplatelet therapy

In the absence of randomized controlled trials to guide antiplatelet therapy for SCAD, data from traditional atherosclerotic ACS literature are extrapolated for this patient population. Aspirin is widely used based on its favorable side-effect profile and extensive literature supporting its benefits in traditional atherosclerotic ACS.²⁶ Patients who undergo stent placement should be treated in accordance with current ACS guidelines and receive dual antiplatelet therapy (DAPT) consisting of aspirin and a P2Y12 inhibitor for 12 months.

For patients who do not undergo PCI, the addition of a second antiplatelet agent is controversial. Expert consensus states that a course of DAPT may be considered² with the goal of minimizing thrombus burden and maintaining patency of the true lumen. While clopidogrel is most commonly prescribed, evidence is limited comparing clopidogrel, ticagrelor, and prasugrel in SCAD. Furthermore, the optimal duration of DAPT is unknown. Some authors recommend treatment for up to 12 months, while others advocate discontinuing the P2Y12 inhibitor after 1 to 3 months or when healing of the dissection is confirmed.²⁷

Although DAPT in SCAD has been shown to be safe in several observational studies, there is a theoretical concern about the use of antiplatelet agents in a disease state that may be triggered by intramural bleeding.²⁸ In a cohort of 64 patients with SCAD,²⁹ 59 (92%) received DAPT with aspirin plus either clopidogrel (69%), prasugrel (14%), or ticagrelor (9%). Of the 40 patients who underwent repeat angiography, healing of dissection was demonstrated in all but 1. DAPT was well tolerated, with no specific medication-related complications noted.²⁹

As of this writing, no data have been published on the use of glycoprotein IIb/IIIa inhibitors in SCAD.

Limited role for anticoagulation

In line with contemporary ACS guidelines, anticoagulation is often appropriately initiated before SCAD is diagnosed. Once SCAD is identified as the cause of ACS, there is no clear benefit to continuing this therapy.² Anticoagulation involves a theoretical risk of increased intramural bleeding and extension of dissection, although there is a paucity of evidence on this. According to expert consensus, anticoagulants should be stopped upon confirmation of SCAD in the absence of another compelling indication for anticoagulation such as left ventricular thrombus or other thromboembolic disease.²⁸ The few published case reports on SCAD complicated by left ventricular thrombus report safe treatment with anticoagulation.³⁰

No role for thrombolysis

Thrombolysis is contraindicated in SCAD, as it may propagate dissection and lead to coronary rupture and cardiac tamponade.²⁸ Several case reports have been published documenting the adverse effects of thrombolysis in SCAD.^31,32

Beta-blockers as tolerated

Beta-blockers are central to the management of acute aortic dissection, reducing shear stress on the vessel wall and minimizing risk of propagation.³³ It follows that they would be similarly beneficial for SCAD. Beta-blockers serve not only to lower blood pressure but also to modulate heart rate, the cornerstone of impulse control. In a recent study of 327 patients with SCAD, beta-blocker use was associated with reduced risk of recurrent SCAD (hazard ratio 0.36, P = .004).⁴ If validated in future studies, these findings would provide the first evidence for recurrence risk-reduction through medical therapy.

In practice, the use of beta-blockers is often limited by hypotension and fatigue, especially as patients are often young women without coexisting hypertension.¹⁰ No studies to date have evaluated the efficacy of different types of beta-blockers, goal heart rate, or blood pressure after SCAD. Nonetheless, it is reasonable to escalate beta-blocker therapy to the maximally tolerated dose. In patients unable to tolerate beta-blockers, a nondihydropyridine calcium channel blocker should be considered.

Lipid-lowering therapy if otherwise indicated

As no proven connection has been identified between cholesterol and risk of SCAD, statins and other lipid-lowering agents are generally reserved for patients with traditional indications for those medications. In a retrospective single-center cohort study of 87 patients, statin use was associated with subsequent risk of SCAD recurrence.¹⁷ However, as this analysis was limited by small sample size and incomplete information on statin use, it should be interpreted with caution. The signal for increased recurrence of SCAD with statin use has not been demonstrated in larger studies.⁴ In the absence of any other indication for lipid-lowering therapy, we do not routinely prescribe statins in patients with SCAD.

Screen for fibromuscular dysplasia and other arteriopathies

Fibromuscular dysplasia is an idiopathic arteriopathy not caused by underlying atherosclerosis or inflammation, with a predilection for medium-sized vessels. It is the condition most commonly associated with SCAD, with an estimated prevalence of 25% to 86%.³⁴ This wide range reflects differences between screening methods and the number of vascular territories screened. The hallmark feature on imaging is the “string of beads,” which occurs where areas of fibrosis (causing narrowing) alternate with regions of dilation.³⁵ The renal, carotid, and vertebral arteries are most often affected, but nearly any site may be involved.

Other arteriopathies associated with SCAD include Marfan syndrome, Loeys-Dietz syndrome, vascular Ehlers-Danlos syndrome, alpha-1 antitrypsin deficiency, and polycystic kidney disease.^7,8

Given these associations, a vascular medicine evaluation is recommended for all patients diagnosed with SCAD. The evaluation should include a comprehensive vascular history, examination, and brain-to-pelvis imaging.¹⁰ Patients with a family history or physical examination findings suggestive of known arteriopathies may benefit from a genetics evaluation. Coronary computed tomography angiography is preferred for imaging when possible, as it has higher spatial resolution than magnetic resonance angiography or ultrasonography. Screening provides valuable data to guide management, develop a longitudinal follow-up plan, and inform prognosis.

Monitor for chest pain and recurrence

Although the prognosis for long-term survival is favorable, patients are at risk of chronic angina, recurrent SCAD, and noncardiac chest pain. Optimal management requires regular follow-up with a cardiologist experienced in the care of SCAD.

Recommend cardiac rehabilitation

Cardiac rehabilitation is an important component of management following SCAD, but it remains significantly underused. Young and otherwise healthy women, comprising the majority of patients with SCAD, are infrequently referred for cardiac rehabilitation. There is also concern about the safety of cardiac rehabilitation in light of the association of SCAD with physical activity.¹⁷ Collectively, these barriers result in low enrollment, adherence, and completion rates.

However, cardiac rehabilitation has clear short-term and long-term benefits for perceived physical and mental health, and it has consistently been shown to be safe in patients with SCAD.^38,39 In a cohort of 70 women with SCAD participating in cardiac rehabilitation, improvements were found in exercise capacity, symptoms (specifically chest pain), and psychosocial well-being at the conclusion of the program.³⁹ Similarly, of the 269 patients who participated in cardiac rehabilitation from the Mayo Clinic SCAD registry, 82% reported physical health benefits and 75% reported emotional health benefits.⁴⁰

We recommend referring all patients with SCAD for cardiac rehabilitation, including young women without other comorbidities. Our aerobic exercise plan involves training set at a target heart rate zone equivalent to 50% to 70% heart rate reserve based on initial exercise stress testing. The frequency of cardiac rehabilitation and aerobic exercise participation should be at least 3 times weekly for 20 to 30 minutes per session as a starting point. As patient fitness and comfort with exercise gradually improve, program progression should be encouraged but implemented conservatively and without including high-intensity interval-training methods. The long-term goal is for patients to comfortably exercise 45 to 60 minutes per session on most days of the week.

Resistance training involving isometric (constant muscle length) contraction, particularly using large muscle groups, should be avoided in patients with a history of SCAD, as these activities are often associated with temporary loading of muscles, closely followed by acute periods of high power and pressure generation.

Similarly, strength training should be limited to light intensity. Greater intensity is typically associated with Valsalva-type maneuvers, which rapidly generate transient bursts of high-to-extreme levels of intrathoracic, cardiac, and aortic pressures. This yields high levels of localized vascular wall mechanical shear stress and compensatory spikes in heart rate, all of which should be avoided in patients with a history of SCAD.