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Getting at the natural history of nonatherosclerotic spontaneous coronary artery dissection (SCAD), a prospective cohort study found the risk of longer-term recurrent dissections and other cardiovascular events to be lower than expected.

Based on 750 consecutive SCAD patients who had presented with heart attacks and were largely treated conservatively, long-term survival was "excellent" given a 3-year mortality rate of just 0.8%, according to Jacqueline Saw, MD, of Vancouver General Hospital, and colleagues of the Canadian SCAD (CanSCAD) cohort study.

Overall major adverse coronary events (MACE) reached 14.0%, which included a 9.9% incidence of recurrent myocardial infarction (MI) that was split into extensions of previous SCAD (3.5%), de novo recurrent SCAD (2.4%), and iatrogenic catheter-induced dissection (1.9%), they reported in the .

"Our finding of low MACE rates and mortality out to 3 years is remarkably low compared with older published reports," Saw's group said. "Previously, MACE rates of up to 30% were reported at follow-up of 2 to 3 years, mostly caused by recurrent MI from recurrent SCAD, which was reported in 15% to 22% of patients."

It is likely that the older registry-based reports had been biased due to the retrospective and prospective enrollment of higher-risk SCAD patients that drove MACE rates artificially higher, the authors suggested.

The present report "suggests a better prognosis and decreased SCAD recurrence rate in less selected, more representative SCAD patients," agreed Alexandre Persu, MD, PhD, of Cliniques Universitaires Saint Luc in Brussels, and colleagues in an . "Overall, these data will provide some reassurance to patients."

It is well documented that younger women are disproportionately affected by SCAD as a cause of MI. Yet many questions remain regarding the natural history and treatments in SCAD due to a dearth of prospective and randomized studies in the literature.

Notably, the large majority of CanSCAD individuals remained on aspirin and beta-blockers through 3-year follow-up. Neither therapy significantly affected 3-year event rates, contrary to prior findings from Saw and colleagues.

"While the latest findings generate more uncertainty about the utility of these medications after SCAD, are underway to address this question," Persu's group noted.

Similarly neutral results were observed in people who underwent in-hospital revascularization in the present cohort study. The nearly 15% of SCAD patients who had received initial revascularization -- percutaneous coronary intervention (PCI) typically reserved for people with ongoing ischemia, and coronary artery bypass grafting (CABG) for those with left main or extensive proximal multivessel SCAD -- had no difference in postdischarge MACE compared with peers managed conservatively.

"We have observed in clinical practice that sometimes the pendulum had swung too much to the conservative side, in which, for instance, patients with ongoing ischemia and ST elevation were treated medically. It is hoped that our data will provide some reassuring evidence that if PCI or CABG need to be pursued, the long-term outcomes post-revascularization would be favorable," Saw's group wrote.

was a prospective, observational study of people who presented with acute coronary syndrome to 22 centers in 2014-2018. Participants had to have nonatherosclerotic SCAD documented on coronary angiography and confirmed by core laboratory results.

The cohort averaged age 51.7 and 88.5% were women. Approximately one in three had ST-segment elevation MI (STEMI), and two in three non-STEMI. Patients reported a precipitating emotional stressor in 50.3% of cases, and a physical stressor in 28.9%.

Predisposing conditions included fibromuscular dysplasia in 42.9%, peripartum state in 4.5%, and genetic disorders in 1.6%. These factors emerged as independent predictors of 3-year MACE on multivariate analysis, though this should be interpreted as hypothesis-generating, the CanSCAD authors cautioned.

They also acknowledged that, despite their efforts to enroll all consecutive SCAD patients, their study did not capture people who died before presenting to hospital, those who did not undergo coronary angiography, and those whose SCAD diagnoses were missed on coronary angiography.

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