Clinical and electrophysiologic findings in patients with repetitive monomorphic ventricular tachycardia and otherwise normal electrocardiogram.

Natural history, structural substrate, electrocardiographic and electrophysiologic characteristics and therapy were evaluated in 18 patients who demonstrated repetitive ventricular tachycardia, defined as repeated episodes of ventricular tachycardia that had a uniform QRS configuration and normal sinus-conducted QRS complexes between the episodes of tachycardia. The patients were young (mean age 37 years) and frequently had a long history of arrhythmias before this evaluation; only two patients has a history of syncope and six were completely asymptomatic. Fourteen patients had no evidence of underlying structural heart disease, three had mitral valve prolapse and one had congestive cardiomyopathy. Episodes of ventricular tachycardia tended to occur in clusters over a 24 hour electrocardiographic recording period. Repetitive ventricular tachycardia was induced in two of nine patients by programmed electrical stimulation, and in seven patients incremental atrial and ventricular pacing suppressed spontaneous arrhythmia. In the one patient whose tachycardia was induced by incremental ventricular pacing there was an inverse relation between pacing cycle length and the interval from the last paced complex to the first complex of ventricular tachycardia, indicating there was overdrive suppression. At a follow-up time of 0.5 to 8 years no patient had died or had worsening of symptoms. Encainide completely eliminated episodes of ventricular tachycardia during acute treatment in five of six patients tested. Seven patients received no antiarrhythmic therapy and the arrhythmia appeared to have spontaneously resolved in four of these patients. Repetitive ventricular tachycardia appears to have distinct clinical and electrophysiologic characteristics. In this series the arrhythmia had a good prognosis and often required no treatment. The electrophysiologic features are consistent with a mechanism of automaticity.