Introduction
An acute increase in the pacing threshold early after pacemaker
implantation is occasionally a problem, even in the era of
steroid-eluting leads. In such cases, bradycardia-dependent increase in
the pacing threshold without apparent lead dislodgement has been
demonstrated to be responsible for micro-dislodgement or phase 4 block
and is expected to recover spontaneously1-2. However,
the mechanism of this phenomenon has not been elucidated.
We herein report a case of a patient who underwent pacemaker
implantation for sick sinus syndrome (SSS), in whom the mechanism of
bradycardia-dependent increase in the pacing threshold was elucidated
using adenosine triphosphate (ATP).