Optimal Pace Timing for Left Bundle Branch Area Pacing with or without an Additional LV Lead: Results from the CSPOT study

BACKGROUND AND AIMS: The study aimed to determine optimal AV timing for left bundle branch area pacing (LBBAP) and optimal AV and VV timing for LBBAP optimized cardiac resynchronization therapy (LOT-CRT), to enhance the benefit of conduction system pacing. METHODS: Acute measurements of LV dP/dtmax and QRS duration were collected during sweeps of AV and VV delays during paired comparison of LBBAP, LOT-CRT, and biventricular pacing (BVP), in 48 CRT-indicated patients. Optimal AV delays were selected as the vertex of a parabolic model fit to the AV sweep results, obtained independently for LV dP/dtmax and QRS duration. RESULTS: LBBAP, LOT-CRT, and BVP were similarly sensitive to the choice of AV delay, and 60ms deviations from optimal AV delay resulted in an approximately 30% reduction in the hemodynamic benefits of resynchronization. Based upon LV dP/dtmax measurements, the average optimal paced AV (PAV) for LBBAP (152ms) was significantly shorter than that for LOT-CRT (171ms, p < 0.01) or BVP (167ms, p = 0.01). Based upon QRS duration, the average optimal PAV for LBBAP (164ms) was similar to that for LOT-CRT (160ms, p = 0.52) or BVP (165ms, p = 0.95). For each resynchronization modality, a linear regression between the patient's measured intrinsic AV conduction and their optimal AV delay provided a patient-specific AV delay, resulting in improved AV selection compared to applying a fixed AV delay to all patients. Finally, simultaneous activation (VV = 0) was best for both LOT-CRT and BVP. CONCLUSION: LBBAP, LOT-CRT, and BVP are similarly sensitive to AV-timing. Optimal AV delay is linearly related to intrinsic AV for each resynchronization modality. For LOT-CRT and BVP, simultaneous biventricular activation is best on average.