Treatment of ventricular arrhythmias after CAST

The primary objective of this article is to review the management of ventricular arrythmias in the light of the unfavourable results reported in the Cardiac Arrhythmia Suppression Trial (CAST).

CAST tested the hypothesis that suppression of ventricular arrhythmias recorded on a Holter monitor in patients with myocardial infarction would lead to a decrease in subsequent mortality, presumably by preventing sudden death. In the trial, patients with a myocardial infarction which occurred six days to two years previously and with asymptomatic ventricular premature beats which could be suppressed by one of the antiarrhythmic agents flecainide, encainide or moricizine, were randomised to treatment with one of these agents or placebo. Over a mean follow-up period of 10 months, mortality was significantly higher in those patients receiving flecainide or encainide than in those receiving placebo. On the recommendation of the Data and Safety Monitoring Board the trial in these groups was terminated. More recently CAST II in which moricizine was compared to placebo was also terminated, again because of a higher mortality in the patients receiving active treatment. It is likely that much of the excess mortality can be attributed to proarrhythmic effects of the agents.

Current management of ventricular arrhythmias are considered in the light of these findings. CAST suggests that specific treatment should be dictated by the presence of associated symptoms and as much by associated structural heart disease as the arrhythmia per se. In particular, specific treatment of ventricular premature beats alone should be avoided. In those with potentially lethal ventricular arrhythmias, referral for appropriate investigation and consideration of non-pharmacological measures is necessary.