Very high acute pacing thresholds during atrial leadless pacemaker implantation: Feasibility of a current-of-injury-guided release strategy.

BACKGROUND: Very high acute pacing thresholds (VHPT) during AVEIR-AR atrial leadless pacemaker (ALP) implantation often prompt device repositioning, although excessive manipulation may increase procedural risk. OBJECTIVE: To evaluate the safety and early electrical performance of ALP release despite VHPT using a current-of-injury (COI)-guided strategy. METHODS: We retrospectively analyzed 28 consecutive patients who underwent AVEIR-AR ALP implantation at two centers in Japan and compared procedural safety and short-term electrical performance between patients with normal PTs (NPT <5.5 V at 0.4 ms) and those with VHPT (≥5.5 V at 0.4 ms). In the VHPT group, ALP device release was permitted when pre-screw COI was adequate (≥1 mV). RESULTS: The mean age was 85±6 years, body weight was 54±8 kg, and 11 patients were female. Single-site pre-mapping successful implantation was achieved in 36%, and repositioning was avoided in 89%, with no dislodgment, tamponade, or PT-related complications observed. Fourteen patients (50%) had VHPT, with comparable COI values between the VHPT and NPT groups (1.5±0.7 mV vs. 1.4±0.7 mV). In the VHPT group, PT improved from 5.9±0.2 V at tether to 5.1±1.4 V after release, 1.3±0.8 V at discharge, and 0.8±0.6 V at 1-month, with the initial between-group difference no longer evident. Sensitivity analyses using alternative cutoff values (≥5.0 V and ≥6.0 V) demonstrated consistent trends. CONCLUSION: VHPT during ALP implantation improved after device release when adequate COI was present. A COI-guided release strategy may be feasible in selected cases and may help reduce mapping and screw attempts while enhancing procedural safety during ALP implantation.