Risk of VF Undersensing in Extra-Vascular ICD Due to Concomitant Leadless Pacing

Extravascular implantable cardioverter-defibrillators (EV-ICD) offer defibrillation, anti-tachycardia pacing (ATP), and backup pacing, packaged in a unit comparable to traditional transvenous ICDs in size, shape, and longevity. However, the pacing capabilities of EV-ICD are restricted to ATP, pause prevention and post-shock pacing. For EV-ICD patients who develop the need for pacing, having a concomitant leadless pacemaker such as Micra could provide the needed pacing support. This research examines the potential interference between Micra's pacing pulses and EV-ICD's arrhythmia detection functions. Specifically, we investigate the impact of pacing amplitudes and pulse widths on the detection of ventricular fibrillation (VF) by the EV-ICD. Our findings indicate that pacing pulses with amplitudes not exceeding 1.3 times the amplitude of VF should not confound VF detection. In our VF database, this threshold corresponds to pacing amplitudes of approximately 0.99±0.56 mV in the sensing electrogram (EGM) vector. Additionally, our analysis identifies pulse width as a critical factor, with widths greater than 0.24 ms, significantly impairing VF detection. These results underscore the importance of proper pacing parameters configuration to optimize the functionality of EV-ICD when combined with a leadless pacemaker.