Induction of polymorphic ventricular tachycardia by programmed ventricular stimulation in vasospastic angina pectoris.

This study was designed to examine the ventricular vulnerability of patients with vasospastic angina. Fourteen patients (mean age 57 +/- 9 years) with vasospastic angina underwent electrophysiologic testing during the asymptomatic phase (baseline) and after the relief of acetylcholine-induced spasm with isosorbide dinitrates. Twenty patients without structural heart disease served as a control group. By programmed ventricular stimulation, polymorphic ventricular tachycardia (VT) was induced at baseline in 6 of 14 patients, with 1 patient developing ventricular fibrillation and 7 of 14 patients developing repetitive ventricular responses. After isosorbide dinitrate, polymorphic VT was induced in only 1 patient who had ventricular fibrillation at baseline. Repetitive ventricular responses were induced in 3 of 5 patients who had VT at baseline and in 4 of the 7 patients with repetitive ventricular responses at baseline. There was a significant difference in the incidences and severity of induced ventricular arrhythmias between the 2 phases (p <0.01). Among 20 control subjects, repetitive ventricular responses were induced only in 6 patients, but no VT was induced. There was a significant difference in the incidence of induced ventricular arrhythmias and VT at baseline between the vasospastic angina and control groups (p <0.001 and <0.01, respectively). Thus, patients with vasospastic 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 vasospastic attacks.