His bundle pacing insights from electroanatomical mapping: Topography and pacing targets

Objectives To characterize 3D electroanatomical mapping (EAM) of the His bundle (HB) region. Background Visualization of selective (S) and nonselective (NS) HB capture areas by EAM has not been described and may help guide HB pacing (HBP). Methods EAM was performed via NavX system in 17 patients (pts) undergoing HBP. HB cloud, S‐HB, NS‐HB, and right bundle (RB) capture areas were mapped. Results S‐HBP areas were identified in 11, NS‐HBP in 14, and RB in 11 pts. Two NS‐HBP areas (upper and lower) either separated by S‐HBP (8 pts) or almost contiguous (5 pts) were observed. S‐HBP area measured: 1.1 ± 0.9 cm2, NS upper: −1.2 ± 0.9 cm2, NS lower: −1.2 ± 0.9 cm2, RB: −1.7 ± 1.3 cm2, total His cloud: −4.1 ± 2.7 cm2. Electrocardiogram (ECG) pacemaps were different between upper and lower NS‐HBP areas in 13/14 pts (p = .006). ECG differences between NS clouds were present in inferior leads in 9 pts (more negative QRS complex from lower NS area) and in precordial leads in 5 pts. There was no correlation between HBP lead location and capture threshold. R‐wave amplitude was higher at more distal locations on HB cloud (p = .02). Conclusion (1) Pacemapping identifies distinct regions that may correspond to HB anatomy. (2) A linear S‐HBP area is typically surrounded by two separate NS areas. (3) Pace‐map ECGs from upper and lower NS‐HBP areas have different morphologies. (4) These EAM features and pace‐mapping may be helpful to the implanter.