Lessons to be learned from the Cardiac Arrhythmia Suppression Trial

Abstract

T he administration of antiarrhythmic drugs is the first and most frequently used approach to therapy of patients with ventricular arrhythmia. The presence of runs of nonsustained ventricular tachycardia on ambulatory monitoring is associated with an increased risk of sudden cardiac death in some groups of patients, including those with a recent myocardial infarction-3 Even when asymptomatic, these patients are often treated with antiarrhythmic drugs to prevent sudden cardiac death although it is unknown if such therapy will prevent this outcome. Previous studies4J have failed to show improved survival and, therefore, antiarrhythmic drugs are of unproved benefit. However, these studies were flawed because therapy was not guided by arrhythmia suppression. Nevertheless, routine care of the postinfarction patient with ventricular arrhythmia has generally involved the use of antiarrhythmic drugs. The recent interim report from the Cardiac Arrhythmia Suppression Trial (CAST) has caused much concern and physicians are now rethinking the use of any antiarrhythmic drug in patients with asymptomatic arrhythmia. Many questions have also been raised about the implications of the CAST report in regard to other groups of patients or with other types of arrhythmias. There are no answers to these questions; thus, it is imperative to review the facts and weigh the risk-benefit ratio for each patient. CAST had its early roots in the National Institutes of Health-sponsored Cardiac Arrhythmia Pilot Study (CAPS). CAPS involved only 500 patients but it served as a feasibility trial for the larger CAST study, which was designed to test the hypothesis that suppression of asymptomatic ventricular ectopy after a myocardial infarction would decrease the incidence of sudden death.6 Results from CAPS indicated that encainide and flecainide, potent new class 1C agents,’ were effective for suppressing ventricular arrhythmia* and the incidence of adverse reactions, including arrhythmia aggravation, was low and indistinguishable from placebo. For this reason they were chosen, along with moricizine, for use in CAST. CAPS was designed to evaluate drug efficacy and tolerance. CAST was designed to assess mortality in patients whose ambient ectopy was suppressed by these drugs using an algorithm commonly employed in clinical practice.