Differential effects of isoproterenol on sustained ventricular tachycardia before and during procainamide and quinidine antiarrhythmic drug therapy.

BACKGROUNDAutonomic modulation, especially increased sympathetic activity may play a role in the genesis of ventricular arrhythmias. The purpose of this study was to determine whether beta-sympathetic stimulation with isoproterenol would alter sustained ventricular tachycardia (VT) circuits similarly during the drug-free and antiarrhythmic drug-treated states.METHODS AND RESULTSTwenty-five patients with repeatedly inducible, hemodynamically stable, sustained VT were evaluated by programmed ventricular stimulation. In the antiarrhythmic drug-free state, isoproterenol (0.03 microgram/kg per minute) shortened the following intervals (in milliseconds; mean +/- SEM; 25 patients; paired t test): sinus cycle length (792 +/- 37 to 568 +/- 18; (p < 0.001), ventricular paced QT interval (386 +/- 8 to 348 +/- 6; p < 0.001), ventricular paced QRS duration (185 +/- 4 to 182 +/- 4; p = 0.014), ventricular effective (238 +/- 5 to 208 +/- 4; p < 0.001) and functional (261 +/- 6 to 227 +/- 5; p < 0.001) refractory periods...