Atrioventricular-synchronous leadless pacemakers: a single center experience

Abstract Background Leadless pacemakers allow atrioventricular (AV) synchronous pacing using a new software to detect atrial contraction with a 3- axis accelerometer. Notwithstanding, evidence supporting its use is still scarce and only limited real-world data have been reported. Aim To evaluate the feasibility and to describe pacing outcomes of AV-synchronous leadless pacemakers. Methods Consecutive patients with AV block referred to leadless pacemaker MicraTM at single center between June 2020 and November 2022 were retrospectively included. Patients were evaluated at two distinct times during follow-up and parameters from sensed atrial tracking were calculated: tracking index (atrial mechanical sense followed by ventricular pace [AM-VP] divided by total VP) and total AV synchrony (sum of AM-ventricular sense [AM-VS], AM-VP, and AV conduction mode switch). Results A total of 43 patients (mean age 78 ± 11 years; 72% male) were included. Pacing indication was complete AV block in 29 patients (67%) and high-grade AV block in the remaining 14 (33%). Mean implantation and fluoroscopy times were 48 ± 22 minutes and 4.5 ± 3.9 minutes, respectively. One major peri-procedural complication was reported: a cardiac tamponade, treated with pericardiocentesis. The first outpatient visit occurred at a mean follow-up of 3.2 ± 4.1 months after the implantation procedure. Overall, at the first screening, 47% of patients required at least 50% pacing; mean tracking index was 65 ± 16% and mean total AV synchrony was 80 ± 18%. Specific pacemaker parameters were adjusted according to physician’s discretion, namely A3 and A4 thresholds and A3 window. Thirty-seven patients performed 2 follow-up visits, 8 ± 5 months after the first visit. In comparative analysis between both follow up times, mean total AV synchrony remained stable (80 ± 17% vs. 80 ± 15%, p=0.970) and there was a numerical improvement of tracking index by 6 ± 13% (65 ± 15% vs. 71 ± 16%, p=0,059). During the follow-up, 7 patients (16%) died, none related to the procedure nor the device. Conclusions Implantation of AV-synchronous leadless pacemakers is feasible and safe. In our cohort, there was a numerical increased of atrial tracking and a stability of AV synchrony during follow-up.