Cardiac Arrhythmia Pilot Study (CAPS)

BACKGROUND:

Epidemiologic studies had indicated that complex ventricular premature beats made an independent contribution to risk of sudden death in survivors of a myocardial infarction (MI), and did not appear to be merely a reflection of their association with relatively severe myocardial damage. The potential for reduction in mortality by identification and administration of drugs capable of safely suppressing ventricular arrhythmias was tremendous. In 1982, there was incomplete knowledge regarding which types of ventricular arrhythmias responded to various kinds of drugs. A pilot study of antiarrhythmic agents helped clarify this issue.

Numerous antiarrhythmic agents with differing pharmacologic properties and side effects had been shown to suppress ventricular arrhythmias. It had also been postulated that antiarrhythmics might raise an individual's threshold for experiencing ventricular fibrillation. There had been several published reports of large (at least l00 patients), long-term clinical trials of antiarrhythmic agents in post-MI patients. None of these had yielded statistically significant results using mortality as the response variable. This might have been due to incorrect drug selection, inadequate sample size, inappropriate choice of patients, or the lack of impact of arrhythmia treatment on mortality.

Due to incomplete knowledge as to which drug(s) and combinations of drugs were most effective, it was considered to be premature to undertake a full scale trial in 1981-1982. However, the public health problem was of sufficient magnitude to warrant a pilot study to learn more about the efficacy and safety of various antiarrhythmic drugs singly or in combination.

The protocol planning phase began in October l982. Patient recruitment started in July l983 and ended in the summer of 1985. Each patient was followed for one year.

DESIGN NARRATIVE:

Randomized, double-blind, fixed sample. A total of 502 patients were randomly assigned to 5 treatment groups consisting of encainide, ethmozine, flecainide, imipramine, and placebo.