[Effects of verapamil and disopyramide phosphate on the termination, reinduction and long-term prevention of paroxysmal supraventricular tachycardia].

The efficacy of verapamil and disopyramide phosphate for the termination and prevention of paroxysmal supraventricular tachycardia (PSVT) were studied electrophysiologically in 32 patients with inducible sustained PSVT (17 patients received verapamil, 15 patients received disopyramide). Twelve patients had atrioventricular nodal tachycardia, 7 had concealed and 13 had overt Wolff-Parkinson-White syndrome. Intravenous verapamil (0.15 mg/kg) terminated the sustained PSVT in 15 of the 17 patients (88%) by production of AV block in 13 patients, VA block in one, and a ventricular premature beat in one. PSVT could not be induced in any of these 15 patients after they had received verapamil. In the remaining 2 patients, PSVT could not be terminated by the use of verapamil, but the cycle lengths of PSVT were lengthened. Long-term oral dosages of verapamil of 120-240 mg/day were administered in 13 of the 17 patients. All patients except two, whose PSVT was unable to be effected by intravenous verapamil, were well controlled: PSVT disappeared in 7 patients and decreased in 4. Intravenous disopyramide (1.5 mg/kg) terminated induced PSVT in 10 of the 15 patients (67%) by production of VA block. Although PSVT could not be reinitiated in 5 of these 10 patients, non-sustained PSVT was induced in 2 and sustained PSVT was induced in 3 after having received disopyramide. PSVT was induced in all of the 5 patients who failed to respond to disopyramide. The cycle lengths of PSVT after administration of disopyramide remained unchanged.(ABSTRACT TRUNCATED AT 250 WORDS)