Histologic Analysis of the Right Atrioventricular Junction in the Adult Human Heart

Background and aim of the study: The human tricuspid valve is conventionally thought to have a fibrous annulus in the septal region. The study aim was to conduct morphological and histological analyses of the right atrioventricular junction (RAVJ), in particular to investigate the fibrous/collagenous content of this structure in the adult human heart.
Methods: Twelve human hearts from patients who died after cardiac surgery and underwent autopsy were included in the study. Rigid exclusion criteria were practiced to ensure that the hearts studied were not subject to ventricular dilatation or hypertrophy prior to surgery, or had undergone valvular surgery. Gross examination of the RAVJ was performed and the entire circumference of the RAVJ sectioned
longitudinally at 5 mm intervals; the tissues were then fixed in 10% neutral buffered formalin for 24 h.
All sections were then stained with hematoxylin and eosin and elastic van Geison stains.

Results: There were no significant amounts of fibrous or collagenous structures along the free wall segment of the RAVJ. Muscular bars, measuring about 2-4 mm in diameter, were seen to run between the wall of the right ventricle and the RAVJ on its ventricular aspect. The relationship between the base of the tricuspid valve leaflet to the right atrial and right ventricular muscle head varied significantly within, and between, hearts.
Conclusion: While the septal aspect of the RAVJ has scant fibrous tissue, the majority of its free wall segment is devoid of fibrous tissue. Right ventricular muscle bridges are inserted into the RAVJ, the functional significance of which, both in normal hearts and in the pathogenesis of functional tricuspid regurgitation, requires further investigation.


The Journal of Heart Valve Disease 2012;21:368-373