The response to procainamide during electrophysiologic study for sustained ventricular tachyarrhythmias predicts the response to other medications.

We evaluated 126 patients with inducible sustained ventricular tachyarrhythmias to assess whether the response to procainamide during electrophysiologic study could predict responses to other conventional antiarrhythmic agents and combinations of agents. Thirty of 42 patients in whom tachycardia was not inducible after the administration of procainamide and 69 of 84 patients in whom ventricular tachycardia was inducible after procainamide underwent serial electrophysiologic studies. Forty-three of 67 antiarrhythmic regimens (64%) tested in the patients in whom ventricular tachycardia could not be induced after procainamide prevented induction of ventricular tachycardia, compared with 10 of 145 regimens (7%) tested in the patients in whom ventricular tachycardia could be induced after procainamide. Sixty of the 69 patients in whom ventricular tachycardia remained inducible after procainamide had ventricular tachycardia induced on all other conventional antiarrhythmic regimens tested. By comparison, of the 30 patients in whom ventricular tachycardia became noninducible after procainamide, 25 had no ventricular tachycardia inducible on at least one other antiarrhythmic regimen tested. Thus, the response to procainamide accurately predicted the response to other conventional antiarrhythmic agents during electrophysiologic study.