Verapamil responsive ventricular tachycardia: clinical and electrophysiologic characteristics.

Ventricular tachycardia is a rare arrhythmia in young patients without associated heart disease. Electrophysiologic studies were performed in thirteen young patients (mean age 26.4 +/- 7 years) with recurrent sustained ventricular tachycardia (VT) responsive to intravenous verapamil. The QRS duration during VT was less than 0.14 sec in all patients. The VT showed a right bundle branch block (RBBB) morphology in all cases, with left axis deviation in 12 and right axis deviation in one. Eleven patients were free of organic heart disease. VT could be induced in the laboratory in 10 patients, out of whom the electrophysiologic mechanism of VT could be assessed in 9 cases. The data were consistent with reentry in 8 patients and suggested triggered activity in one patient. Atrial pacing induced the VT in two cases. Nine patients were restudied 48 to 72 hours after oral verapamil (240 to 320 mg/day). VT was not inducible in 8 patients and was markedly slowed in one. VT of RBBB morphology occurring in young patients has distinct electrocardiographic and electropharmacologic properties. Reentry is the usual underlying mechanism. Verapamil is highly effective in terminating and preventing the VT.