SCAD heart attacks: results not as bad as previously feared

To follow the natural history of non-atherosclerotic spontaneous coronary artery dissection (SCAD), a prospective cohort study found that the risk of longer-term recurrent dissections and other cardiovascular events was lower than expected.

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

The total number of major adverse coronary events (MACE) reached 14.0%, including a 9.9% incidence of recurrent myocardial infarction (MI) resulting in prolongation of previous SCAD (3.5%), de novo recurrent SCAD (2, 4%) and iatrogenic catheter-induced dissection (1.9%), they reported in the Journal of the American College of Cardiology.

“Our finding of low MACE rates and mortality up to 3 years is remarkably low compared to older published reports,” said Saw’s group. “Previously, MACE rates of up to 30% have been reported with 2 to 3 years of follow-up, mainly caused by recurrent myocardial infarction due to recurrent SCAD, reported in 15% to 22% of patients.”

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

The present report “suggests a better prognosis and reduced SCAD recurrence rate in fewer selected, more representative SCAD patients,” agreed Alexandre Persu, MD, PhD, of Cliniques Universitaires Saint Luc in Brussels, and colleagues in an accompanying editorial. “Overall, these data will give patients some reassurance.”

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

Notably, the vast majority of CanSCAD subjects remained on aspirin and beta-blockers throughout the three-year follow-up. Neither therapy significantly affected the 3-year event rates, in contrast to previous findings by Saw and colleagues.

“While the latest results create more uncertainty about the usefulness of these drugs after SCAD, prospective randomized controlled trials are underway to answer this question,” noted Persus Gruppe.

Similar neutral results were observed in subjects undergoing in-hospital revascularization in the present cohort study. The nearly 15% of SCAD patients who received initial revascularization—percutaneous coronary intervention (PCI) typically reserved for people with persistent ischemia, and coronary artery bypass graft (CABG) surgery for those with left-sided or extensive proximal multivessels -SCAD – had no difference in MACE after discharge compared to conservatively treated peers.

“We have observed in clinical practice that the pendulum has sometimes swung too much to the conservative side, where, for example, patients with persistent ischemia and ST elevation were medicated PCI or CABG need to be pursued, which would be long-term outcomes after revascularization cheap,” Saw’s group wrote.

CanSCAD was a prospective observational study of people presenting to 22 acute coronary syndrome centers between 2014 and 2018. Participants were required to have non-atherosclerotic SCAD documented by coronary angiography and confirmed by core laboratory results.

The mean age of the cohort was 51.7 years and 88.5% were women. About one in three had ST segment elevation MI (STEMI) and two in three did not have STEMI. Patients reported a triggering emotional stressor in 50.3% of cases and a physical stressor in 28.9%.

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

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