Imaging Measurements
Images were uploaded to a processing software (Aquarius iNtuition Viewer, TeraRecon, Inc., Durham, NC, version 4.4.13.P7) that allowed for 3-dimensional reconstruction of images and measurements. 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 (Figure 1A ). From there, a line was extended to the RV apex in RAO view to mirror standard clinical conditions (Figure 1B ). Next, the first septal perforator was identified. The complete course of the artery was not always visible. Therefore, a line connecting the artery ostium to the previously drawn His-RV line was drawn in order to standardize measurements across patients (Figure 1C ). To ensure standardization, the line was drawn so that it would intersect with the His-RV line at a measured 90-degree angle. Finally, the distance between the previously located His bundle and the intersection of the septal perforator line was measured and recorded (Figure 1D ).