Predictors of increase in pacing threshold after transcatheter pacing system implantation due to micro‐dislodgement

Abstract

Background: Achieving a favorable pacing threshold with a Micra transcatheter pacing system (Micra-TPS) is needed to reduce battery depletion. In some cases, the threshold increases shortly after the device is implanted, and a higher pacing threshold may be required. This study aims to identify the causes and predictors of the increase in pacing threshold observed shortly after Micra-TPS implantation. Methods: The study included 64 consecutive patients who underwent Micra-TPS implantation between 2017 and 2020. The patients were divided into two groups depending on their pacing threshold: the increased pacing threshold (IPT) group (threshold increased by ≥0.5 V/0.24 ms within 1 month of implantation) and the stable pacing threshold (SPT) group. Results: Excluding four patients who could not be followed up, of the 60 remaining patients, nine (15%) were in the IPT group and 51 (85%) were in the SPT group. The IPT group had significantly lower implant impedance values and higher implant thresholds than the SPT group (582 ± 59 vs 755 ± 167 Ω [P < .001] and 1.29 ± 0.87 vs 0.71 ± 0.40 V/0.24 ms [P = .014]). Implant impedance and threshold may serve as predictors of a threshold increase after implantation (area under the curve: 0.737-0.943 and 0.586-0.926, respectively). Conclusions: An IPT was noted shortly after Micra-TPS implantation owing to microdislodgement because of insufficient anchoring of the device to the myocardium. Impedance >660 Ω and threshold <1.0 V/0.24 ms may predict an increase in pacing threshold.

Fluoroscopic predictors of acceptable capture threshold during the implantation of the micra transcatheter pacing system

“…Kiani et al 10 showed that a pacing impedance of <800 Ω at implantation was related to an elevated capture threshold at 12 months. Other reports have identified a pacing impedance at implantation of >600 Ω or 660 Ω as a predictor of an acceptable threshold 11,12 . The low impedance may indicate a poor contact of the Micra TPS with the myocardium.…”

“…The pacing impedance after fixation has been reported to be associated with the capture threshold during the follow‐up period 10–12 . Kiani et al 10 showed that a pacing impedance of <800 Ω at implantation was related to an elevated capture threshold at 12 months.…”

“…Other reports have identified a pacing impedance at implantation of >600 Ω or 660 Ω as a predictor of an acceptable threshold. 11,12 The low impedance may indicate a poor contact of the Micra TPS with the myocardium. In the present study, pacing impedance was significantly higher in the acceptable threshold group than that in the high threshold group.…”

“…The pacing impedance after fixation has been reported to be associated with the capture threshold during the follow-up period. [10][11][12] Kiani et al 10 showed that a pacing impedance of <800 Ω at implantation was related to an elevated capture threshold at 12 months. Other reports have identified a pacing impedance at implantation of >600 Ω or 660 Ω as a predictor of an acceptable threshold.…”

A broken tine as a possible explanation for rise in pacing threshold in a leadless pacemaker

“…Predictors of increased pacing threshold in the Micra device have been investigated. 9 Higher acute pacing thresholds and lower impedances at implant predict elevated pacing thresholds, presumed secondary to poor tissue contact. Our patient had an excellent acute threshold and normal impedance at implant.…”