Implementation of a new DDDR algorithm for tachycardia prevention and treatment utilizing an implantable RAM-based software-controlled pacemaker.

Reentry within the atrioventricular node or over accessory pathways are common causes of symptomatic tachycardia. These arrhythmias are frequently initiated by a spontaneous atrial or ventricular premature beat. Appropriately timed atrial or ventricular extrastimuli can, in some patients, render one limb of the reentrant circuit refractory and prevent induction of tachycardia. Currently available implantable devices are not suitable for this application. The authors have implemented a new implantable pacing algorithm capable of extremely short atrial and ventricular refractory periods, rapid triggered ventricular pacing rates, protection against encroachment on the ventricular vulnerable period, protection against tachycardia induction by ventricular premature beats, automated antitachycardia pacing in either atrium and ventricle, as well as an extensive event storage capability. This application has been made possible by a new, RAM-based microprocessor controlled dual chamber pacemaker (Medtronic Prometheus Model 6100). Its use in intraatrial tachycardia with atrioventricular block as well as Wolff-Parkinson-White syndrome is demonstrated. This device is capable of prevention of tachycardia induction in some patients. Where prevention is not feasible or fails, it is backed up by automated or manually activated antitachycardia pacing. The great flexibility of a completely reprogrammable software based pacemaker has enabled the implementation of a very complex experimental pacemaker that will permit evaluation in the implanted setting of this new pacing strategy.