Bradycardia-Dependent Transient Rise in the Atrial Lead Capture Threshold 21 Years After the Lead Implantation.

We present a man with an implantable cardioverter defibrillator implanted for Brugada syndrome. Twenty-one years later, he underwent catheter ablation of atrial fibrillation and tachycardia. Bradycardia-dependent transient loss of atrial capture was observed 3 months post-ablation, undetected by the automatic pacing threshold adjustment algorithm performed at a pacing rate higher than the programmed setting. We report a transient bradycardia-dependent rise in the capture threshold over 20 years post-implantation, along with its mechanism.