Predictive factors for increase in pacing threshold after transcatheter
pacing system implantation owing to micro-dislodgement
Abstract
Introduction: Achievement of a favorable pacing threshold with a Micra
transcatheter pacing system (Micra-TPS) is important for reducing
battery depletion; in some cases, the threshold increases shortly after
the device is implanted, and a higher pacing threshold may be required.
This study aimed to define the causes and predictors of the increase in
pacing threshold observed shortly after Micra-TPS implantation. Methods
and Results: The study included 64 consecutive patients who underwent
Micra-TPS implantation between 2017 and 2020. Patients were divided into
two groups depending on their pacing threshold, namely, the increased
pacing threshold (IPT) group (threshold increased by ≥0.5 V/0.24 msec
within 1 month of implantation) and the stable pacing threshold (SPT)
group. Excluding 4 patients we were unable to conduct follow-up on, 9 of
the 60 remaining patients (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 <0.001) and 1.29 ± 0.87 vs 0.71 ± 0.40
V/0.24 msec (P =0.014), respectively. 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).
Conclusion: An increased pacing threshold was noted shortly after
Micra-TPS implantation owing to micro-dislodgement because of
insufficient anchoring of the device on the myocardium. Impedance
>660 Ω and threshold <1.0 V/0.24 msec may be
predictive factors for an increased pacing threshold.