The AV junction region of the heart: a comprehensive study correlating gross anatomy and direct three-dimensional analysis. Part II. Morphology and cytoarchitecture

Abstract

Racker, Darlene K. The AV junction region of the heart: a comprehensive study correlating gross anatomy and direct threedimensional analysis. Part II. Morphology and cytoarchitecture. Am J Physiol Heart Circ Physiol 286: H1853-H1871, 2004; 10.1152/ ajpheart.01205.2003.-This "Part II morphology and cytoarchitecture" study is based on paraffin-embedded specimens in which the extracellular and intracellular matrix are preserved; single parallel, perpendicular, and transverse serial sections of the entire atrioventricular (AV) junction region (AVJR) and their correlation with photographs of the tissue blocks. As in Part I, the same major new findings are: 1) a coronary sinus fossa is formed by the superoposterior right medial atria wall (MAW), the left atrium, and the coronary sinus roof; 2) the posterior MAW forms two myocardial bridges and is isolated from the sinus venarum by the floor of the inferior vena cava; 3) the tendon of Todaro terminates in the superior lip of the coronary sinus ostium; 4) only ordinary myocardium contacts the annulus fibrosus, and there is little to no collagen separating its myofibers and tissues; 5) the ventricular septum shoulder is humped shaped, completely overlaid by annular myocardium, and joined by struts of papillary muscle; 6) the membranous septum joining the ventricular septum shoulder to the crista supraventricularis forms part of the aortic valve sinus walls; and 7) myocardium of the atrionodal bundles is aggregated into numerous small fascicles encased by collagen and is outside of the MAW as are the other specialized tissues. The proximal AV bundle and medial atrionodal bundle are aligned to the medial leg of Koch's triangle and the tendon of Todaro. These data show, therefore, that the AVJR contains two overlapping atrial circuits. In the MAW, acivation of the posterior region is delayed because of the two myocardial bridges. Puncture of the AVJR can produce communication with an extracardiac space, posteriorly and medially, and with the aorta, anteriorly.

A–V nodal artery anatomy and relations to the posterior septal space and its contents

“…In addition, we have found that the right lower wall is relatively smaller than the left lower wall because of the normal malalignment between the tricuspid and mitral annuli. It is generally acknowledged that the triangle of Koch, containing the AV node in its anterior part [15], forms the right upper surface of the PSS and our results confirm that.…”

Right Atrial Approach for Ablation of Ventricular Arrhythmias Arising From the Left Posterior–Superior Process of the Left Ventricle

“…Superiorly, at the apex of the triangle lies the right fibrous trigone and the posterior aspect of the atrio-ventricular membranous septum. [1][2][3][4][5][6][7] The inferior wall of the RA lies above and lateral to the PSP-LV adjacent to the pyramidal space. The CS orifice is medial to this area.…”

Learning While Burning Revisited

“…In “slow‐fast” AVNRT, the reentry circuit consists of anterograde conduction through the slow pathway and retrograde conduction by the fast pathway with the earliest retrograde atrial activation in the “fast pathway region” at the apex of the triangle of Koch, recorded on the His‐bundle electrogram from the right septum 9,10 . Unfortunately, life is not that simple: the three‐dimensional anatomy and cytoarchitecture of the AV junction is complex 11,12 and the exact location of the atrionodal connections and slow and fast pathways are still controversial. Although several elegant models based on functional characteristics of different areas of the compact AV node and surrounding structures were proposed to explain dual‐AV node physiology, the sheer bulk of the literature on the subject and the ongoing debate attest that none of them is proven 13,14 .…”