A 63-year-old female with sinus node dysfunction underwent to implantation of dual-chamber pacemaker (Reply DR, Sorin Group CRM USA, Inc.) programmed in SafeR mode (AAI< = >DDD). Two months later, she referred a presyncopal episode. Device interrogation showed atrial fibrillation (AF) associated to complete atrioventricular (AV) block and ventricular escape rhythm at 35 bpm.
SafeR-pacing-mode provides AAI-pacing while continuously monitoring AV conduction. Mode switch criterion due to atrial arrhythmia is related to a probabilistic counter of premature atrial events. Window of atrial rate acceleration detection (WARAD) is initiated with the sensing of an atrial event corresponds to 62.5% of previous PP-interval. Mode switching occurs if ≥2× 18 of 32 cycles are detected in WARD. In non-conducted atrial arrhythmias, pacemaker switches to DDD-mode if a ventricular pause ≥2 or 3 s (in this case programmed 2 s) is detected and to DDI after arrhythmia confirmation. However, escape rhythm presented an RR-interval <2 s, so device did not pace the ventricle until arrhythmia was confirmed (64 cycles = 2× 18 of 32) and switched to DDI. In consequence, complain of the patient was compatible with a time of 17 s at 35 bpm (Figure).
The full-length version of this report can be viewed at: http://www.escardio.org/communities/EHRA/publications/ep-case-reports/Documents/Switch-to-DDD-mode.
