Antiarrhythmic effects of oral indecainide in patients with ventricular tachyarrhythmias.

In order to assess the efficacy and safety of oral indecainide in patients with serious ventricular arrhythmias we studied 11 patients with high-grade ventricular ectopy and ventricular tachycardia (VT) which were refractory to therapy with at least one standard antiarrhythmic drug. Spontaneous arrhythmias were quantitated by 24-h Holter monitor before and during therapy with indecainide. Spontaneous VT was sustained in 4 patients and nonsustained in 7. Ten patients underwent baseline electrophysiologic study (EPS) and VT was induced in 9. The mean ejection fraction was 25 +/- 14%. Indecainide was given orally at a dose of 211 +/- 118 mg/day. The frequency of ventricular premature beats (VPBs) was significantly (greater than 85%) decreased in 90% of patients, while ventricular couplets frequency decreased in 78%. Spontaneous VT was abolished in 5 of 11 (45%). Sustained VT was induced in 5 of 7 (71%) patients who underwent follow-up EPS. The QRS duration was significantly prolonged during therapy (0.13 +/- 0.04 s) compared to control (0.10 +/- 0.02 s). The PR, QTc, and JTc intervals were not significantly changed. Indecainide was well tolerated, but 2 patients died of ventricular tachyarrhythmias while receiving the drug. Indecainide suppressed VPBs in a high percentage of patients, but was much less successful in controlling VT. Caution is necessary when using this drug because of its potential for exacerbation of arrhythmia.