A Case Report: Electrotonic Modulation-Related T-Wave Over-Sensing After Left Bundle Branch Pacing.

A 66-year-old male patient diagnosed with dilated cardiomyopathy, heart failure with reduced EF (32%), and complete left bundle branch block (CLBBB) received cardiac resynchronization therapy (CRT)-D implantation. Left bundle branch pacing (LBBP) was successfully performed, but during the follow-up 6 weeks later, the electrocardiogram (ECG) showed a sinus rhythm tracked by ventricular pacing with a ratio of approximately 2:1 due to T-wave over-sensing, which might be caused by the changes in T-wave morphology due to electrotonic modulation and hyperkalemia or by the lower sensitivity threshold set by the auto sensing algorithm of the ICD. Shortening post-ventricular atrial refractory period (PVARP) restored the ventricular pacing tracking of the atrium, and the T-wave changes improved as time went by.