Complete Left Bundle Branch Block Resolution After Cardiac Resynchronization Therapy With Serial Phonocardiographic Changes.

BACKGROUND

Cardiac resynchronization therapy (CRT) induces structural and electrical reverse remodeling in patients with heart failure. However, resolution of complete left bundle branch block (CLBBB) following CRT has rarely been described, particularly with serial phonocardiographic assessment.

CASE SUMMARY: A 67-year-old man with heart failure associated with atrial fibrillation and CLBBB underwent CRT pacemaker implantation following pulsed-field ablation. Initially, the optimal interventricular (VV) delay required left ventricular pre-excitation, but shifted toward right ventricular pre-excitation after 1 month. Three months after CRT implantation, CLBBB resolved and left ventricular function nearly normalized. Phonocardiography demonstrated an increased peak-to-peak amplitude of the first heart sound and the disappearance of the third and fourth heart sounds.

DISCUSSION: This case illustrates progressive electrical reverse remodeling reflected by serial changes in optimal VV delay settings and phonocardiographic findings.

TAKE-HOME MESSAGE: Temporal changes in optimal VV delay settings may reflect recovery of intrinsic ventricular conduction after CRT.