The electrocardiographic, clinical, and electrophysiologic spectrum of idiopathic monomorphic ventricular tachycardia.

Clinical, ECG, and electrophysiologic data from 47 patients who had episodes of sustained or nonsustained monomorphic VT with no evidence of structural heart disease were reviewed. According to the QRS configuration during tachycardia, four groups were distinguished. Nine patients had a right bundle branch block configuration and superior frontal plane QRS axis (group 1). Nine patients had a right bundle branch block configuration but an intermediate or right QRS axis (group 2). Group 3 consisted of five patients with a left bundle branch block configuration and a left axis deviation, and in group 4 there were 24 patients who had a left bundle branch block configuration with an intermediate or right frontal axis. Patients in group 1 had dizziness during tachycardia less frequently, but they needed cardioversion to terminate their arrhythmias more often. They experienced tachycardia during exercise less often, and tachycardia was not initiated during exercise testing. They had fewer ventricular premature beats according to the Holter recording. During the electrophysiologic study, VT was induced and terminated by pacing more often in this group. Patients with idiopathic VT with a right bundle branch block configuration and a superior axis seem to be a unique group of patients with idiopathic VT, and reentry seems to be the most likely arrhythmia mechanism in this group. The other ECG configurations share the same clinical and electrophysiologic characteristics, which suggest that the underlying arrhythmia mechanism is the same.