A case of repeated rate-dependent pacing threshold elevation after leadless pacemaker implantation.

The pacing threshold is important for leadless pacemakers, as the pacing output has a significant impact on battery longevity. Acute pacing rate-dependent threshold increases have also been reported with leadless pacemakers. In the present case, we experienced a case in which the threshold, which had been raised in the acute phase, once showed a tendency to improve, but then worsened again. And, as in previous reports, thresholds improved completely in the chronic phase. Repeated retrieval and reimplantation of leadless pacemakers increases the likelihood of fatal complications, so being aware of such phenomenon may prevent unnecessary procedure and complications.