Vulnerability of the ventricular conduction axis during transcatheter aortic valvar implantation: A translational pathologic study

Abstract

The ventricular components of the conduction axis remain vulnerable following transcatheter aortic valvar replacement. We aimed to describe features which may be used accurately by interventionalists to predict the precise location of the conduction axis, hoping better to avoid conduction disturbances. We scanned eight normal adult heart specimens by 3T magnetic resonance, using the images to simulate histological sections in order accurately to place the conduction axis back within the heart. We then used histology, tested in two pediatric hearts, to prepare sections, validated by the magnetic resonance images, to reveal the key relationships between the conduction axis and the aortic root. The axis was shown to have a close relationship to the nadir of the right coronary leaflet, in particular when the aortic root was rotated in counterclockwise fashion. The axis was more vulnerable in the setting of a narrow inferoseptal recess, when the inferior margin of the membranous septum was above the plane of the virtual basal ring, and when minimal myocardium was supporting the right coronary sinus. The features identified in our study are in keeping with the original description provided by Tawara, but at variance with more recent accounts. They suggest that the vulnerability of the axis during transcatheter valvar replacement can potentially be inferred on the basis of knowledge of the position of the aortic root within the ventricular base. If validated by clinical studies, our findings may better permit avoidance of new‐onset left bundle branch block following transcatheter aortic valvar replacement.

Multi-modality imaging evaluation and pre-surgical planning for aortic valve-sparing operations in patients with aortic root aneurysm

“…Care is taken to differentiate the membranous septum from the superiorly positioned interleaflet triangle and adjacent transverse sinus (white star). (D) Recent investigations support the common adjacency of the left bundle and its superior fascicle to the nadir of the right coronary leaflet as depicted in this illustration ( 25 , 32 ). N, non-coronary sinus; L, left coronary sinus; R, right coronary sinus.…”

“…The penetrating bundle will penetrate at the anterior margin of the roof of the inferoseptal recess. The non-branching bundle will then course under the inferior margin of the membranous septum with the left bundle branch originating near the anterior aspect of this inferior margin, and its superior fascicle coursing immediately inferior to the nadir of the right coronary leaflet ( 25 , 30 , 32 ). In the clockwise positioned root, the proximal ventricular components will then be positioned outside of the circumference extending below the virtual basal ring plane.…”

“…In the counterclockwise positioned root, the inferoseptal recess becomes narrow and shallow, bringing these proximal components into this circumference, with the left bundle branch commonly extending further anteriorly and in close proximity to the nadir of the right coronary leaflet. These relationships in the counterclockwise positioned root pose increased vulnerability to iatrogenic damage ( Figure 4E ) ( 32 ).…”

“…The central fibrous body is comprised of the right fibrous trigone, the roof of the inferoseptal recess of the left ventricular outflow tract, and the membranous septum ( Figure 10 ) ( 30 , 32 , 54 ). Whereas the right fibrous trigone is the rightward thickening of the area of fibrous continuity between the anterior leaflet of the mitral valve and the leaflets of the aortic valve, the roof of the inferoseptal recess represents the fibrous tissue between the atrioventricular valves.…”

“…Recent histological investigations have confirmed this anatomy. The left bundle branch and its superior fascicle often continue to ascend the crest of the muscular ventricular septum towards the nadir of the right coronary leaflet, positioned an average distance of only 3 mm inferior to the plane of the virtual basal ring at this location ( 25 , 32 ). This is intuitive in light of the findings that measuring the relationship of the anterior aspect of the inferior margin of the membranous septum to the plane of the virtual basal ring ( Figure 10C ), and comparing to valve implantation depth following transcatheter aortic valve replacement was highly predictive of subsequent conduction damage ( 31 , 58 ).…”