Programmed simultaneous biventricular stimulation in man, with special reference to its use in the evaluation of intraventricular reentry.

Programmed stimulation was alternatively performed exclusively from the right ventricular endocardium, exclusively from the left ventricular epicardium and simultaneously from both ventricles in 8 patients who did not have coronary artery disease or bundle branch block. A specially constructed QRS triggered pacemaker, (with a refractory period of 260 msec and an escape interval of 800 msec) connected to the right ventricular and left ventricular electrodes, was used to perform simultaneous biventricular stimulation. The latter had no untoward effects and was not more dangerous than exclusive right ventricular, or exclusive left ventricular, stimulation. In 3 patients, pacemaker-induced repetitive firing occurred during right and left ventricular pacing. Persistence of this phenomenon (in these 3 patients) during simultaneous biventricular stimulation is in keeping either with a microreentry occurring in the vicinity of the electrodes or with a macroreentry involving the bundle branches. A more precise evaluation of the reentry circuit requires that left ventricular pacing be performed from an endocardial (rather than from an epicardial) site. This study suggests that the pulse generator described in the present communication can be used to produce simultaneous atrial and ventricular activation (or pacing) by connecting one pole to an atrial electrode and the other pole to a ventricular electrode. This modality of stimulation can be effective in preventing or abolishing some types of reciprocating atrioventricular tachycardias.