Incidence of reentry with an excitable gap in ventricular tachycardia: a prospective evaluation utilizing transient entrainment.

The demonstration of transient entrainment has been proposed as evidence of reentry, with an excitable gap as the probable mechanism of tachycardia. A prospective series of 27 consecutive patients with sustained ventricular tachycardia induced by programmed electrical stimulation was studied to determine the frequency with which transient entrainment can be demonstrated and to define the optimal location of pacing and recording electrodes. In all patients, electrodes for pacing and recording were placed in both the left and right ventricles during electrophysiologic study. Among the 19 patients in whom the response to rapid pacing could be evaluated (25 episodes of ventricular tachycardia), transient entrainment was demonstrated in 79% (76% of episodes). Ten of 12 episodes of ventricular tachycardia with a left bundle branch block QRS configuration in lead V1 and 9 of 13 episodes with a right bundle branch block QRS configuration could be transiently entrained (p = NS). Transient entrainment was demonstrated for 8 of 11 episodes of ventricular tachycardia with a left bundle branch block configuration during pacing from the left ventricle, but for only 2 of 10 episodes during pacing from the right ventricular apex (p less than 0.05). Conversely, 9 of 13 episodes of ventricular tachycardia with a right bundle branch block configuration were transiently entrained during pacing from the right ventricular apex, but 0 of 10 episodes were transiently entrained by left ventricular pacing (p less than 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)