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).