Comparison of the antiarrhythmic efficacy of disopyramide and mexiletine against stimulus-induced ventricular tachycardia.

Programmed ventricular stimulation was used to assess the effect of oral disopyramide (600 mg/day), mexiletine (600--1000 mg/day), and a combination of both drugs in a randomized cross-over study on 12 patients with documented ventricular tachycardia and/or fibrillation. In two cases, all three types of treatment were ineffective in that ventricular tachycardia could still be initiated under the same conditions. In four cases, disopyramide and mexiletine alone were ineffective or the change in inducibility was only slight. However, when both drugs were administered in combination, ventricular tachycardia was more difficult to induce or was no longer inducible. In two other cases, disopyramide was the more effective drug. In the remaining four patients, all three types of treatment were similarly effective. In patients whose ventricular tachycardia remained inducible its rate decreased from 188 +/- 45 bpm (control) to 170 +/- 40 bpm on disopyramide, 172 +/- 31 bpm on mexiletine, and 146 +/- 39 bpm on disopyramide plus mexiletine. Long-term therapy was based on the results of acute testing. Seven patients received both disopyramide and mexiletine and tolerated this therapy well during a follow-up of 42 +/- 23 weeks. Two sudden deaths occurred, one possibly due to dose reduction and one in a patient in whom short bursts of ventricular tachycardia remained inducible during acute testing. We conclude that the combined administration of disopyramide and mexiletine is effective and safe in patients with ventricular tachycardia. It is tolerated without major side effects even during long-term therapy.