Mechanical Properties and Composition of the Basal Leaflet-Annulus Region of the Tricuspid Valve.

The Tricuspid valve (TV) annulus is a transition structure from the leaflets to the myocardium, with 3 different annulus segments corresponding to the TV leaflets, which includes both basal leaflets and bordering myocardium. The objective of this study was to understand TV annulus mechanical properties and correlate it to the biological composition. The uniaxial testing of the annulus segments from ten porcine TVs was performed to measure Young's modulus (E) and extensibility (εT). Western blotting and histology were executed. The septal annulus E value (208.7 ± 67.2 kPa) was statistically greater (p < 0.01) than that of the anterior (92.0 ± 66.8 kPa) and the posterior annulus segment (136.8 ± 56.9 kPa) (p < 0.05), respectively. εT among the 3 segments were equivalent (p values < 0.05). Western blotting and histology indicated that collagen was greatest along the septal annulus segment, which is correlated to E values. Collagen fibers from the leaflets inserted into the myocardium and faded out. Collagen content explains greater E and suture strength in the surgical annulus repair and larger resistance to annulus dilation in the septal annulus as compared with other segments. This study elucidates new knowledge of mechanical properties of the basal leaflet-annulus region of the TV annulus, which can be useful for future TV repair techniques.