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 excellent (≥0.78).

CONCLUSION

These findings further infer the intimate yet highly variable relationship between the conduction axis and aortic root. This reproducible and standardized approach needs validation in populations of patients requiring accurate identification of the atrioventricular components of the conduction axis, which may serve as a noninvasive means for estimating its location.