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Revascularization for silent ischemia was associated with better outcomes in the long run compared with medical therapy alone, a registry study suggested.

Mortality was 19% lower with revascularization for asymptomatic stable coronary artery disease (CAD) than with medication alone over more than 4 years' follow-up (11.9% vs 18.6%, HR 0.81, 95% CI 0.69-0.96), according to researchers led by Andrew Czarnecki, MD, MSc, of Sunnybrook Health Sciences Centre in Toronto, Ontario.

Heart attack was 42% less likely over the same period after percutaneous coronary intervention (PCI) or coronary artery bypass graft (CABG) surgery (3.8% vs 6.5%, HR 0.58, 95% CI 0.46-0.73) in the study of patients who had angiography, published online in .

These apparent benefits were consistent across revascularization strategies and hospital-level variation in use of them. The lower death and MI rates also persisted whether a patient went into angiography with or without left ventricular dysfunction.

"These findings suggest that a selective revascularization strategy based on factors (such as high risk anatomic distributions) most likely to confer prognostic benefit is safe, and combined with optimal medical therapy, may offer the best clinical outcome," the authors said. "However, these findings should be considered hypothesis generating and not be used as justification for routine revascularization of all coronary stenosis in asymptomatic patients."

"Unfortunately, little evidence is available to guide clinical decision-making in asymptomatic patients, as only small subsets of these patients were included in previous studies," they wrote.

The better outcomes associated with revascularization were relatively surprising, because cardiac therapies seldom lead to such reductions in MI risk, commented Stephen Ellis, MD, of the Cleveland Clinic, in an .

The cohort study included patients in an Ontario registry with the Canadian Cardiovascular Society class 0 angina and substantial stenosis in a major coronary vessel (n=9,897). Of this group, 53% received revascularization within 90 days of the angiogram, with PCI done more often than CABG.

Notably, 10.9% of the medical therapy-only group did end up getting revascularization within 1 year.

Predictors of revascularization included lower age, female sex, high-risk anatomic features, lack of medical comorbidities, and angiography by an interventional cardiologist.

Practice varied substantially among hospitals: their ratios of revascularization vs medical therapy for silent ischemia ranged from under 0.80 to more than 1.60 (average 1.12). The variation couldn't be totally explained by patient, physician, or hospital factors, Czarnecki's group found.

They acknowledged that they studied the "atypical group" of asymptomatic patients undergoing coronary angiography and raised the issue of potential selection bias in their analyses.

A wide array of non-cardiac causes of death makes it hard to properly adjust risk in this kind of observational study, Ellis said.

"Before deciding how much credence to give the results of this study, and how we will manage these patients until better data become available, we also have to decide how to define and diagnose periprocedural MI for both PCI and CABG," the editorialist added, noting that Czarnecki and colleagues omitted their definitions of peri-procedural and late MI.

Ultimately, more of these stable CAD patients should be enrolled in trials, Ellis urged. He pointed to the ISCHEMIA trial that includes patients with silent ischemia and is to be presented in 2019.