Novel cardiac CT method for identifying the atrioventricular conduction axis by anatomic landmarks

BACKGROUND Understanding the conduction axis location aids in avoiding iatrogenic damage and guiding targeted heart rhythm therapy. OBJECTIVE Cardiac structures visible with clinical imaging have been demonstrated to correlate with variability in the conduction system course. We aimed to standardize and assess the reproducibility of predicting the location of the atrioventricular conduction axis by cardiac computed tomography. METHODS We evaluated 477 patients with acquired aortic valve disease by cardiac computed tomography to assess variability in cardiac structures established to relate to the conduction system. We standardized 3 points (points A-C) to estimate the course from the atrioventricular node to the nonbranching bundle and left bundle branch origin and further compared this with measures of variability in the aortic root and membranous septum. RESULTS The mean distances between the aortic valve virtual basal ring and points A, B, and C were 9.5 +/- 3.5 (0.3-20.1) mm, 5.0 +/- 2.6 (-1.7 to 15.9) mm, and 2.9 +/- 2.5 (-5.2 to 12.0) mm, respectively. The midpoint of the membranous septum deviated posteriorly a median of -4.4 (interquartile range, -12.4 to +3.0) degrees relative to the commissure between the right coronary and noncoronary leaflets. Intraclass coefficients for both intraobserver and interobserver variability for all measured points were of the atrioventricular components of the conduction axis, which may serve as a noninvasive means for estimating its location.