IMPORTANCE OF PACEMAKER NOISE REVERSION AS A POTENTIAL MECHANISM OF PACEMAKER-ICD INTERACTIONS

Numerous types of interactions between pacemakers and implantable card ioverter defibrillators (ICDs) have been described. Pacemaker outputs preventing appropriate defection of ventricular tachycardia or ventric ular fibrillation by the ICD is one of the more serious. Asynchronous pacemaker activity during ventricular arrhythmias map be caused by eit her nonsensing of the arrhythmia or by noise reversion, which is an al gorithm that causes the pacemaker to switch to asynchronous pacing whe n repetitive sensing at a high rate occurs. We analyzed the mechanisms underlying asynchronous pacemaker activity in ventricular arrhythmias using pacemaker telemetry during the arrhythmia. Thirty-nine induced arrhythmias from 26 different procedures in 19 patients with both pace makers and ICDs were analyzed. Of the 39 arrhythmias, asynchronous pac emaker activity occurred in 16. The underlying mechanism was nonsensin g in 4 episodes and noise reversion in 12 episodes. Clinically signifi cant interference with detection arose on three occasions. Conditions favoring the occurrence of noise reversion include specific pacemaker models, arrhythmia cycle lengths in the range causing noise reversion of the individual pacemaker model, long noise sampling periods, and VV I pacing mode. Noise reversion can be diagnosed by telemetering the pa cemaker marker channel during ventricular arrhythmias as a part of rou tine pacemaker-ICD interaction evaluation. It can be prevented or mini mized by programming short ventricular refractory periods or using pac emakers with short retriggerable refractory periods.