Defining the Distance Between the His Bundle and Septal Perforator Arteries

Introduction: Left bundle branch pacing (LBBP) is an emerging pacing modality in which the LBBP lead is screwed through the interventricular septum towards the left bundle branch in the left septal subendocardium. Damage to a septal perforating branch of the left anterior descending coronary artery is a potential complication. Objective: To define the distance between the His bundle and the first septal perforator artery to guide safe LBBP lead placement. Methods: Clinically indicated coronary CT angiograms (CCTA) at our institution were reviewed. The intersection of the tricuspid annulus and the base of the non-coronary cusp of the aortic valve represented the location of the His bundle. The intersection of a line joining the His bundle location with the RV apex with the first septal perforator was determined. The distance between the His Bundle and this intersection was measured and recorded. Values were analyzed using standard statistical methods. T-tests were used for continuous variables. Results: A total of 50 consecutive CCTAs were included in this study, 30 men and 20 women, average age 55.4 ± 14.1 years. Medical history included HTN (64%), and diabetes (50%) and CAD (10%). LVH was present in 9 patients (18%) but was mild in all cases. Heart failure was present in 9 patients (18%), 4 of whom had systolic dysfunction with an average EF for the study being 57.0%. The mean left ventricular internal diameter at end diastole (LVIDd) and interventricular septum thickness (IVS) were 46.7 mm and 10.2 mm, respectively. The mean distance from the His Bundle to the first septal perforator was 27.2 ± 7.7 mm, median 26.9 mm, range 13.0 to 44.7 mm. There was no significant difference by gender for mean distance (28.1 mm men vs 25.6 mm women, p=0.26). There was no significant association between LVIDd or IVS and the His Bundle-Septal Perforator distance (r 2 =0.02 and r 2 =0.002, respectively). Conclusions: Using CCTA, we defined the distance between the His bundle and the first septal perforator. Operators implanting LBBP leads can use these measurements to guide safe lead placement.