Antianginal agents may improve outcomes in silent ischemia without CAD

Patients with silent ischemia but no coronary artery disease (CAD) may benefit from treatment with antianginal drug therapy, according to results of the Swiss Interventional Study on Silent Ischemia Type I (SWISSI I) presented during the American College of Cardiology's 56th annual scientific session.

"Despite the known beneficial effect of antianginal therapy on prognosis in patients with silent ischemia and documented CAD, it has been unknown whether this is also true for asymptomatic subjects without prior CAD," said Paul Erne, MD, professor, department of cardiology, Kantonsspital, Luzern, Switzerland.

In this pilot study sponsored by the Swiss Heart Foundation, 263 asymptomatic patients without prior CAD but with at least one risk factor for CAD were confirmed to have silent ischemia by an exercise electrocardiogram followed by stress imaging.

The 54 patients consenting to participate were randomized in an open label trial to receive antianginal drug treatment with one of several agents (n=26) or to risk factor control only (n=28). Patients ranged in age from 45 to 75 years, 69% were male, and all had normal left ventricular ejection fraction. They were followed for a mean of 11.2 years and were examined at 3, 6, and 12 months, and annually thereafter.

Cardiac death, nonfatal myocardial infarction, and unstable angina requiring medical treatment or revascularization procedures occurred in 12% of the patients taking antianginal medication and 61% of those randomized to risk factor control alone. This was an absolute event reduction per year of 6.9% in favor of medical treatment, Dr. Erne said.

He emphasized that this highly significant difference in outcomes occurred despite the majority of patients in the risk factor control arm being successful with adhering to parameters. For example, more than 60% of patients stopped smoking, up to 89% adhered to treatment for dyslipidemia, and a similar majority adhered to blood pressure control regimens.

Furthermore, patients receiving antianginal treatment had lower rates of exercise-induced ischemia during follow-up and their ejection fraction remained unchanged. Patients participating in the risk factor control arm, however, experienced a 6% decrease in ejection fraction.

"Drug therapy tended to reduce the signs of ischemia and to preserve left ventricular function. In patients with verified silent ischemia, prophylactic drug therapy should be considered," Dr. Erne said.