Comparison of 1st and 2nd generation leadless pacemaker in sinus rhythm patients with chronic ventricular pacing for complete atrioventricular block

FUNDING ACKNOWLEDGEMENTS: Type of funding sources: None. BACKGROUND: Leadless pacemakers (LPMs) represent a seductive alternative to conventional pacing. First generation of Micra transcatheter pacing system was able to provide single-chamber VVI(R) pacing mode only, with a potential risk of pacemaker syndrome in sinus rhythm patients. A 2nd generation system (AV) now provides atrioventricular synchrony through atrial mechanical sensing capability (VDD mode). PURPOSE: We sought to compare VR and AV systems in patients with sinus rhythm and chronic ventricular pacing for complete atrioventricular block. METHODS: All consecutive patients implanted with an LPM in our department for complete atrioventricular block were retrospectively screened. Patients with atrial fibrillation, sinus dysfunction, or ventricular pacing burden <20% at 1-month post-implantation were excluded. RESULTS: A total of 80 patients – 35 VR (2015-2020) and 45 AV (2020-2021) – were included. VR and AV patients had similar baseline characteristics, except for that VR patients being older (82±8 versus 77±9 years, p=0.01). Mean ventricular pacing burden was 75% in the VR and 79% in the AV group (p=0.63). In AV patients, median atrioventricular synchronous beats rate was 77%, 67% having a >66% rate. An E/A ratio <1 as measured on echocardiography was the only independent predictor of accurate atrial mechanical tracking (adjusted OR=13, p=0.006). One-year survival rate was 86% in the VR group and 95% in the AV group (adjusted p=0.21). Two patients in the VR and 0 in the AV group eventually developed pacemaker syndrome in the 1st year post-implantation (p=0.07). CONCLUSION: In sinus rhythm patients with chronic ventricular pacing for complete atrioventricular block implanted with an LPM, atrial mechanical sensing algorithm allowed significant atrioventricular synchrony in most patients, and was associated with no occurrence of – otherwise rare – pacemaker syndrome.