High dose caffeine and ventricular arrhythmias.

The effect of high dose caffeine on ventricular arrhythmias was examined in 35 patients with recent myocardial infarctions. All patients received caffeine 450 mg or placebo on separate days using a randomized double-blind study design. Continuous Holter electrocardiographic recordings were performed for 8 h. Caffeine ingestion did not cause any increase in the frequency or complexity of ventricular ectopy with 19 of 35 patients experiencing ventricular arrhythmias after caffeine compared with 24 of 35 with placebo. Serious ventricular ectopic activity (including ventricular couplets and tachycardia) was similar on both study days. Moderately high doses of caffeine do not appear to increase ventricular arrhythmias in this patient population with ischemic heart disease.