Beat-to-beat mode switching for effective ventricular rate control in the presence of atrial tachyarrhythmias – How to maintain a stable ventricular rhythm

Abstract

Background: Mode switching aims to maintain a ventricular rhythm that matches metabolic needs during both sinus rhythm and atrial tachyarrhythmias. This allows patients with atrial arrhythmias to benefit from AV synchronous pacing modes.Aim and method: Beat-to-beat mode switching in Diamond and Clarity pacemakers is designed to maintain a relatively stable ventricular rhythm, ensuring consistent ventricular filling patterns. Atrial tachyarrhythmia detection is based on a continuous analysis of the atrial rhythm. A too rapid increase of the atrial rate with a beat-to-beat acceleration > 15 bpm is considered to be an atrial tachyarrhythmia. Mode switching occurs on detection of the first premature atrial event: atrial tracking is stopped and the ventricular rate is determined by the rate indicated by the dual sensor (QT interval and activity). Atrial pacing restores AV synchrony immediately after cessation of the atrial tachyarrhythmia, effectively avoiding retrograde conduction. Dedicated diagnostic functions allow one to monitor the incidence of atrial tachyarrhythmias and to study atrial and ventricular events just prior to its onset. Both the mode switching and rate responsive function are fully automatic, rendering follow-up procedures easy and less time-consuming. Conclusion: Reliable detection of all atrial events is essential to guarantee appropriate mode switching. Therefore, the pacemaker stores the distribution of the amplitude of all atrial events, both during sinus rhythm and atrial tachyarrhythmias, which facilitates the appropriate programming of the atrial sensitivity.