Prevalence and Periprocedural Value of Current of Injury at the Implantation of a Passive Fixation Leadless Pacemaker.

BACKGROUND: Current of injury (COI) predicts stability and acute improvement in electrical parameters in transvenous pacing or high-voltage leads; however, the periprocedural value of this marker in leadless pacemakers (LLPs) is unknown. METHODS: From March 2021 to October 2022, 66 consecutive Micra LLP pacemaker candidates were enrolled. Electrograms (EGMs) and electrical measures were acquired immediately after the deployment and 5 min after. The primary outcomes were an acute reduction in pacing threshold and, conversely, a need for device repositioning. RESULTS: Fifty-one patients were included in the final analysis after excluding poor-quality EGMs and pacemaker-dependent cases (n = 15). COI was identified in 32 (62%). There were no differences in the initial electrical measures between the COI+ and COI- groups (p value = 0.33, 0.37, 0.89 for impedance, pacing threshold, and sensing, respectively). Notably, the capture threshold significantly improved only in the COI+ group within 5 min (p = 0.002). A subgroup analysis of COI+ revealed that the saddleback type of injury (Type 2) was associated with a more significant acute reduction in the capture threshold (p = 0.02). Repositioning occurred in three subjects, and acute dislodgment at the tug-test occurred in two patients, all from the COI- group. CONCLUSIONS: COI is associated with an acute improvement of capture threshold, particularly when a Type 2 pattern is noted. The absence of injury, in contrast, could reflect inadequate fixation and a need for repositioning.