Optimal pace timing for left bundle branch area pacing with or without an additional LV lead: results from the CSPOT study

This study aimed to determine optimal atrioventricular (AV) timing for left bundle branch area pacing (LBBAP) and optimal AV and interventricular (VV) timing for LBBAP optimized cardiac resynchronization therapy (LOT-CRT) to enhance the benefit of conduction system pacing.

Acute measurements of LV dP/dt_max 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/dt_max and QRS duration. LBBAP, LOT-CRT, and BVP were similarly sensitive to the choice of AV delay, and 60 ms deviations from optimal AV delay resulted in an approximately 30% reduction in the haemodynamic benefits of resynchronization. Based upon LV dP/dt_max measurements, the average optimal paced AV (PAV) for LBBAP (152 ms) was significantly shorter than that for LOT-CRT (171 ms, P < 0.01) or BVP (167 ms, P = 0.01). Based upon QRS duration, the average optimal PAV for LBBAP (164 ms) was similar to that for LOT-CRT (160 ms, P = 0.52) or BVP (165 ms, 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.

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.

https://clinicaltrials.gov/study/NCT04905290