Effects of encainide, flecainide, imipramine and moricizine on ventricular arrhythmias during the year after acute myocardial infarction: the CAPS.

The National Heart, Lung, and Blood Institute initiated the Cardiac Arrhythmia Pilot Study (CAPS) to evaluate the feasibility of suppressing ventricular arrhythmias after acute myocardial infarction. Ten centers enrolled 502 patients younger than 75 years of age with greater than or equal to 10 ventricular premature complexes (VPC) per hour in a 24-hour electrocardiographic recording and a left ventricular ejection fraction greater than 20%. Patients were enrolled 6 to 60 days after acute myocardial infarction and randomized to 1 of 5 treatment tracks with 2 drugs that included encainide, flecainide, imipramine, moricizine or placebo. During a double-blind drug and dose selection phase, investigators were permitted to change drug or dosage to achieve greater than or equal to 70% suppression in VPC frequency and greater than 90% suppression of runs of VPC with the exception of patients assigned to placebo, who continued receiving it. Patients were followed for a year after randomization. Patients in the 5 treatment arms were similar in age, sex, clinical characteristics, VPC frequency, left ventricular ejection fraction and concomitant drug treatment. As first drugs, encainide and flecainide had higher efficacy rates, 79% and 83%, respectively, than imipramine, 52%, moricizine, 66%, or placebo, 37%. Encainide and flecainide also had high efficacy rates, 68% and 69%, in patients who failed imipramine or moricizine. Encainide, flecainide and moricizine were well tolerated. These 3 drugs had intolerable adverse effect rates of 6% or less, i.e., similar to placebo. More than 70T of the patients who started the follow-up phase on encainide, flecainide or moricizine remained on these drugs to the end of the study.(ABSTRACT TRUNCATED AT 250 WORDS)