Results of a ventricular stimulation protocol using a maximum of 4 premature stimuli in patients without documented or suspected ventricular arrhythmias.

A prospective study was undertaken to assess the results of an aggressive ventricular stimulation protocol in 52 nonmedicated patients without a documented or suspected ventricular arrhythmia (VA). Thirty-five patients had no structural heart disease, 8 coronary artery disease, 6 hypertrophic cardiomyopathy, 2 mitral valve disease and 1 patient had congestive cardiomyopathy. The patients were 12 to 72 years old. One to 4 ventricular premature beats (twice diastolic threshold, 2 ms in duration) were given during sinus rhythm and during ventricular pacing at 100 beats/min at the right ventricular apex. End points were initiation of 6 or more beats of VA or every extrastimulus brought to its refractory period. In 31 of 52 patients (60%), a VA was initiated (nonsustained polymorphic ventricular tachycardia in 24 patients, nonsustained monomorphic ventricular tachycardia in 2 and ventricular fibrillation requiring countershock in 5). Repetitive ventricular responses (RVR) (1 to 5 beats) were initiated in 46 patients. In 15 patients only RVRs were initiated. In 6 patients RVRs or VA were not initiated. At the end of the follow-up period (mean 14 months), no patient had spontaneous VA and all were alive. This study shows that ventricular stimulation can result in initiation of VA in patients without clinical VA. Interpretation of results of programmed ventricular stimulation in patients without clinically documented VA should be made with caution.