A shorter R wave peak time in left bundle branch pacing may not be a marker of more physiological ventricular activation: A case report.

Left bundle branch pacing (LBBp) is a promising alternative to conventional biventricular pacing cardiac resynchronization therapy. The left anterior fascicle (LAF) is adjacent to the left ventricular outflow tract, while the left posterior fascicle (LPF) dominates a broader area of the left ventricle. Whether LAF or LPF dominates ventricular activation has not been determined. We present the case of a 76-year-old man who underwent LBBp implantation and propose the left ventricular activation domination in LPF pacing, an alternative when LBBp is unavailable.