Preliminary Studies with an Implantable Multimodal A-V Pacemaker for Reciprocating Atrioventricular Tachycardias

The efficacy of a recently developed programmable implantable pacemaker which can be used in the management of supraventricular tachycardias (with, or without, associated bradyarrhythmias) was evaluated in the cardiovascular laboratory and at the bedside in the coronary care unit. Although this pacemaker functions primarily in a DVI-DVO mode, it was also made (iatrogenically) to operate in a DOO mode. The study was performed in six patients with reciprocating atrioventricular tachycardias (four of the long P-R--short R-P type and two of the short P-R--long R-P type). Both DVI-DVO and DOO pacing abolished all episodes of tachycardia in five of the patients. However, DOO pacing was also capable of initiating episodes of tachycardia in two of the six patients. The events observed in two of the patients raise the possibility that (reversed) ventriculoatrial sequential pacing may be required in some tachycardias of the short P-R--long R-P type. This preliminary study suggests that programmability of pacing modes, rates, and intervals is a desirable feature that pacemakers used to manage drug-resistant tachycardias should have.