Relationship between the membranous septum and the virtual basal ring of the aortic root in candidates for transcatheter implantation of the aortic valve

Abstract

Knowledge of the anatomy of the membranous septum, as a surrogate to the location of the atrioventricular conduction axis, is a prerequisite for those undertaking transcatheter implantation of the aortic valve (TAVI). Equally important is its relationship of the virtual basal ring. This feature, however, has yet to be adequately described in the living heart. We analyzed computed tomographic angiographic datasets from 107 candidates (84.1 ± 5.2 years, 68% women) for TAVI. Using multiplanar reconstructions, we measured the height and width of the membranous septum, and the distances of its superior and inferior margins from the virtual basal ring plane. We also assessed the extent of wedging of the aortic root between the mitral valve and the ventricular septum. Mean heights and widths of the membranous septum were 6.6 ± 2.0, and 10.2 ± 3.1 mm, respectively, with its size significantly associated with that of the aortic root (P < 0.05). Its superior and inferior margins were 4.5 ± 2.3 and 2.1 ± 2.1 mm, respectively, from the plane of the basal ring. The inferior distance, the surrogate for the adjacency of the atrioventricular conduction axis, was ≤ 5mm in 91% of the patients. Deeper wedging of the aortic root was independently correlated with a shorter inferior distance (β = 0.0569, P = 0.0258). The membranous septum is appreciably closer to the virtual basal ring than previously appreciated. These findings impact on estimations of the risk of damage to the atrioventricular conduction axis during TAVI. Clin. Anat. 31:525-534, 2018. © 2018 Wiley Periodicals, Inc.

The rotational position of the aortic root related to its underlying ventricular support

“…This is particularly true with regard to the extent of rotation observed in adults. In this instance, our findings differ slightly from those obtained in our previous clinical investigations (Mori et al, ; Tretter et al, ). Most of the hearts were obtained from historical archives dating back many decades.…”

“…It follows that more children than adults had hearts positioned in counterclockwise fashion within the base of the left ventricle. Our prior clinical studies assessing variability in the rotational position of the aortic root revealed a similar proportion of clockwise and counterclockwise positioned aortic roots in adults (Mori et al, ; Tretter et al, ). This suggests the small sampling of specimens in the current study of both pediatric and adult hearts may not be fully representative of the normal population.…”

“…Our findings also showed no association between the inferior margin of the membranous septum relative to the virtual basal ring and the extent of rotation of the root. Instead, this variation is known to be related to the variation in the position of the entirety of the membranous septum relative to the virtual basal ring (Mori et al, ). The inferior margin of the membranous septum reflects, in turn, the location of the atrioventricular conduction axis relative to the virtual basal ring (Anderson et al, ).…”

“…Although the membranous septum retains its location relative to the aortic root irrespective of the variation in rotation, several studies have shown variability in its dimensions (Icten and Tetik, ; Teofilovski‐Parapid et al, ; Tretter et al, ). There is further variability in its position relative to the virtual basal ring, which represents the echocardiographic valvar annulus (Mori et al, ). The relationship between the degree of rotation of the root and the variation in its ventricular support has yet to be elucidated.…”

What is the real cardiac anatomy?

“…The apical parts of these triangles separate the ventricular cavities from the pericardial space (Anderson, ; Mori et al, ). The triangle between the non‐coronary and right coronary sinuses of the aortic root is particularly significant (Tretter et al, ; Mori et al, ), since it is continuous proximally with the membranous part of the septum (Fig. ).…”