Three‐dimensional visualization of the bovine cardiac conduction system and surrounding structures compared to the arrangements in the human heart

Abstract

In the human heart, the atrioventricular node is located toward the apex of the triangle of Koch, which is also at the apex of the inferior pyramidal space. It is adjacent to the atrioventricular portion of the membranous septum, through which it penetrates to become the atrioventricular bundle. Subsequent to its penetration, the conduction axis is located on the crest of the ventricular septum, sandwiched between the muscular septum and ventricular component of the membranous septum, where it gives rise to the ramifications of the left bundle branch. In contrast, the bovine conduction axis has a long non-branching component, which penetrates into a thick muscular atrioventricular septum having skirted the main cardiac bone and the rightward half of the non-coronary sinus of the aortic root. It commonly gives rise to both right and left bundle branches within the muscular ventricular septum. Unlike the situation in man, the left bundle branch is long and thin before it branches into its fascicles.These differences from the human heart, however, have yet to be shown in threedimensions relative to the surrounding structures. We have now achieved this goal by injecting contrast material into the insulating sheaths that surround the conduction network, evaluating the results by subsequent computed tomography. The fibrous atrioventricular membranous septum of the human heart is replaced in the ox by the main cardiac bone and the muscular atrioventricular septum. The apex of the inferior pyramidal space, which in the bovine, as in the human, is related to the atrioventricular node, is placed inferiorly relative to the left ventricular outflow tract. The bovine atrioventricular conduction axis, therefore, originates from a node itself located inferiorly compared to the human arrangement. The axis must then skirt the non-coronary sinus of the aortic root prior to penetrating the thicker muscular ventricular septum, thus accounting for its long non-branching course. We envisage that our findings will further enhance comparative anatomical research.

The Interventricular Septum: Structure, Function, Dysfunction, and Diseases

“…The atrioventricular node is located at the apex of the Koch triangle, whereas the bundle of His divides at the juncture of the fibrous and muscular boundaries of the IVS into the left and right bundle branches (LBB and RBB, respectively). The LBB subsequently divides into anterior and posterior fascicles, which course towards the anterior and posterior papillary muscles of the LV, whereas the RBB courses down the right side of IVS near the endocardium in its upper third, deeper in the muscular portion of the IVS in the middle third, and then again near the endocardium in its lower third [ 13 ].…”

Lack of evidence for longitudinal dissociation of the atrioventricular conduction axis

“…The study of the canine hearts was approved by the Institutional Animal Care and Use Committee of the Extremadura University, and conforms to the Guide for the Care and Use of Laboratory Animals. These datasets have already been analyzed to determine the overall arrangement of the atrioventricular conduction axis (De Almeida, Macías, et al 2021; De Almeida, Mori, et al, 2021).…”

“…Our own earlier studies, nonetheless, have suggested that sections revealing the arrangement of the cardiomyocytes in their long axis could provide direct evidence of interconnections between them, a point not previously stressed or investigated. The bovine non‐branching bundle, furthermore, is particularly suited to three dimensional assessment, since as already indicated, it can be injected with India Ink (De Almeida et al, 2015, 2017; De Almeida, Mori, et al, 2021; Lhamon, 1912). It can then be analyzed stereoscopically if rendered transparent (De Almeida et al, 2015, 2017).…”

Dynamical behavior analysis of the heart system by the bifurcation structures

“…Once it has received this information, to adapt its frequency to meet the needs of the body, it initiates the electrical impulse which evolves with a frequency adapted to the needs of the body [ 7 , 8 ]. To model the heart system three main nodes among the six heart nodes are considered, namely the sinus node (SA node), the atrioventricular node (AV node) and the Purkinje fibres (PF node) [ 9 , 10 ].…”