Abstract 15482: Variation in Right Atrial Sizes Affects Locations of the His Bundle and Coronary Sinus Os

Abstract

Background: Difficulties in HIS bundle (HBP) and coronary sinus (CS) lead delivery may be contributed by differences in right atrial (RA) anatomy. The distance from the lateral superior vena cava / right atrial junction (SVC) to the HIS bundle or CS os reflects the distance required by a delivery sheath to reach the cannulation target. However, RA geometry is not well characterized using standard 2D echo, but is well characterized by cardiac computed tomography (CT) and invasive electroanatomic mapping (EAM). Objective: The objective of this study is to characterize the variations in the distance from the SVC-RA JXN to the 1) HIS bundle and 2) coronary sinus os, and determine the correlation of these distances to standard measurements obtained from 2D echo. Methods: Cardiac CT (256 slice), electroanatomic maps, and 2D echo from patients undergoing ablation for atrial and ventricular arrhythmias were analyzed using 3D modeling software (Horos). The distances from the SVC were measured to the HIS and CS os on the CT which were co-registered to electroanatomic mapping (Fig 1A). Pearson’s coefficient analysis was performed to assess the correlation of these RA measurements with standard left-sided 2D echo measurements. Results: 41 patients (age 6210 yrs, 31% female, 69% AF ablation) were analyzed. The mean distance between SVC-HIS was 37.2 mm 8.3 mm (range 22-56mm), and the mean distance between SVC-CS os was 66.1 mm 10.1 mm (range 49-92mm), Fig 1B. Both RA measurements correlated (Fig 1B) with LA volume index (R=0.6, p<0.001) but not LV diameter (R=0.079, p=0.3). Conclusion: The distance from the SVC/RA JXN to the HIS and CS os varies widely and may contribute to difficulties in HIS bundle and CS lead implantation. In the absence of pre-procedural cardiac CT or EAM, left atrial measurements from 2D echo may correlate with RA dimensions. Prospective studies are needed to test whether these measurements may help predict optimal delivery sheath sizes for HBP and CS lead placement.