Electrical parameters for physiological His–Purkinje pacing vary by implant location in an ex vivo canine model

Background: Permanent His-bundle pacing (HBP) is an attractive, perhaps more physiological, alternative to traditional right ventricular pacing. Objective: The purpose of this study was to utilize direct visualization to more comprehensively understand the anatomy central to HBP, correlating electrical lead performance to implant locations along the His-bundle (HB) pathway. Methods: Canine hearts (n = 5) were isolated and reanimated using Visible Heart methodologies. Medtronic 3830 SelectSecure leads were fixated where His potentials were present. The location of each implant was mapped/binned into 4 regions approximately analogous to the proximal, penetrating, and distal HB. Locational differences in HBP capture and resultant QRS morphology were assessed. Results: Average HBP capture thresholds did not significantly vary with respect to implant location (1.0-ms pulse width; P =.48). The resulting QRS morphologies from HB-paced beats varied in relation to implant location. As leads were placed further distally along the HB, the ratio of paced to native QRS complex duration increased (ΔQRS _paced /ΔQRS _native ratios—region 2: 0.84 ± 0.16; region 3: 1.04 ± 0.42; region 4: 1.74 ± 0.86). Conclusion: We demonstrated correlation between the anatomic locations of HBP lead placement and resultant QRS morphologies in a reanimated canine heart model. Proximal placement along the HB pathway resulted in more favorable QRS morphologies, suggesting improved selective HBP capture, with no significant increase in HBP capture thresholds. Pacing the HB in more proximal pathway locations improved the selectivity of HBP and may confer electrical and anatomic benefits relative to distal HBP.