Treatment of life-threatening ventricular tachycardia with encainide hydrochloride in patients with left ventricular dysfunction. The Encainide-Ventricular Tachycardia Study Group.

Encainide, a newly released class IC antiarrhythmic agent, was studied in 193 patients with ventricular tachycardia (VT) and depressed left ventricular ejection fraction or important arrhythmia-related symptoms. Therapy was evaluated by 24-hour continuous Holter monitoring if patients had nonsustained VT or by electrophysiologic testing if they had sustained VT. Holter monitoring was used in 99 patients and electrophysiologic testing in 94 patients. At baseline the mean age, percent men, percent with coronary artery disease and mean ejection fraction in the 2 groups was 62 versus 58 years, 76 versus 72%, 62 versus 89%, and 27 versus 30%, respectively. In the Holter monitoring group, 71 of 99 (72%) responded with a significant reduction in VT (35% received 25 mg 3 times day, 47% received 35 mg 3 times a day, 14% received 50 mg 3 times a day and 4% received 50 mg 4 times a day). Adverse cardiac effects in these patients included a 7% incidence of serious proarrhythmic events that were probably related to encainide and a 2% incidence of sick sinus syndrome. In this group no patient developed congestive heart failure that was clearly attributed to encainide. Using electrophysiologic testing, 14 of 94 (15%) had sustained VT rendered noninducible, whereas 18 of 94 (19%) additional patients had partial electrophysiologic response defined as a more tolerable, slower VT. Overall, 32 of 94 (34%) were believed to be effectively treated in this group and were treated with encainide long-term. In the population evaluated by electrophysiologic testing, serious proarrhythmic events occurred in 15 of 94 (16%) and 3% had sinus pauses.(ABSTRACT TRUNCATED AT 250 WORDS)