INDUCTION OF POLYMORPHIC VENTRICULAR-TACHYCARDIA BY PROGRAMMED VENTRICULAR STIMULATION IN VASOSPASTIC ANGINA-PECTORIS

This study was designed to examine the ventricular vulnerability of pa tients with vasospastic angina. Fourteen patients (mean age 57 +/- 9 y ears) with vasospastic angina underwent electrophysiologic testing dur ing the asymptomatic phase (baseline) and after the relief of acetylch oline-induced spasm with isosorbide dinitrates. Twenty patients withou t structural heart disease served as a control group, By programmed ve ntricular stimulation, polymorphic ventricular tachycardia (VT) was in duced at baseline in 6 of 14 patients, with 1 patient developing ventr icular fibrillation and 7 of 14 patients developing repetitive ventric ular responses. After isosorbide dinitrate, polymorphic VT was induced in only 1 patient who had ventricular fibrillation at baseline. Repet itive ventricular responses were induced in 3 of 5 patients who had VT at baseline and in 4 of the 7 patients with repetitive ventricular re sponses at baseline. There was a significant difference in the inciden ces and severity of induced ventricular arrhythmias between the 2 phas es (p < 0.01), Among 20 control subjects, repetitive ventricular respo nses were induced only in 6 patients, but no VT was induced. There was a significant difference in the incidence of induced ventricular arrh ythmias and VT at baseline between the vasospastic angina and control groups p < 0.001 and < 0.01, respectively). Thus, patients with vasosp astic angina had increased ventricular vulnerability, even during the symptom-free period without ischemic events, which could predispose to the development of life-threatening arrhythmias aggravated by vasospa stic attacks.