Bifascicular pacing: a novel multipoint left conduction system pacing method for cardiac resynchronization.

Background: Pacing a single fascicle of the left bundle branch leads to a delay of the segments served by the contralateral fascicle. Bifascicular (BiF) pacing may offer better cardiac resynchronization therapy (CRT) than left inferior fascicle (LIF) or left superior fascicle (LSF) pacing alone.

Objective: To compare synchrony between BiF and single fascicle pacing and present the procedural, clinical, electrocardiographic and echocardiographic outcomes in CRT candidates who received BiF pacing METHODS: The following parameters were investigated to assess acute differences in electrical and mechanical synchrony: paced QRS duration and QRS area, global R-wave peak time (RWPT) and dV/dt time in lateral leads (I, aVL and V6), global longitudinal strain (GLS), peak strain dispersion (PSD) and global work efficiency (GWE). All measurements were performed during BiF, LIF and LSF pacing.

Results: 28 CRT candidates (age: 74.6 ±12.2 years; 36% female; LVEF = 37.2% ±10.6%) received BiF pacing. Compared to single fascicle pacing, BiF pacing resulted in significantly shorter QRS duration, lower QRS area, shorter global RWPT, shorter global dV/dt time, higher GLS and GWE, and lower PSD; no differences were observed between LIF and LSF pacing with respect to these parameters. Lead I dV/dt time and lead I RWPT correlated with mechanical dyssynchrony, especially with PSD (r = 0.79 and r = 0.67).

Conclusion: BiF pacing is a novel physiological pacing method that more completely recruits the left conduction system. Compared to single fascicle pacing, it improves electrical and mechanical synchrony, potentially translating to superior clinical outcomes.