Tachyarrhythmias associated with programmable automatic atrial antitachycardia pacemakers

A multiprogrammable automatic antitachycardia pacemaker (Cybertach-60), connected to a tined "J" wire electrode, was positioned in the right atrial appendage in three patients with recurrent supraventricular tachycardia (SVT). Mechanisms of SVT included atrioventricular (AV) nodal reentry (two patients) and reciprocating tachycardia using an accessory pathway (one patient). Indications for implantation included frequent symptomatic episodes, multiple drug failures, and reproducible termination of the arrhythmia by the automatic pacemaker during electrophysiologic studies. Following discharge, multiple episodes of pacemaker malfunction were recorded. The three types of malfunction included: undersensing with induction of SVT by a single atrial premature depolarization, oversensing of extraneous electromechanical potentials triggering burst pacing which initiated SVT, and inappropriate burst pacing in response to sinus tachycardia with and without initiation of SVT. Treatment with a beta-blocking agent prevented pacemaker triggering by sinus tachycardia, and replacement of the electrode catheter resolved pacemaker triggering by electromechanical potentials. One patient required removal of the pacemaker because undersensing could not be corrected by repositioning the atrial electrode. This report illustrates three potential complications that may result with either normal or faulty sensing when employing automatic atrial antitachycardia pacemakers for control of SVT. It also stresses the importance of careful electrophysiologic evaluation before implantation and meticulous follow-up after implantation.