Suture dehiscence and collagen content in the human mitral and tricuspid annuli

Postoperative suture dehiscence is an important mode of short-term mitral and tricuspid valve (MV, TV) repair failure. We sought to evaluate suture pullout forces and collagen density in human atrioventricular valves for a better understanding of the comparative physiology between the valves and the underlying mechanobiological basis for suture retention. Mitral and tricuspid annuli were each excised from hearts from human donors age 60-79 with no history of heart disease (n = 6). Anchor sutures were vertically pulled until tearing through the tissue. Suture pullout force (F_P) was measured as the maximum force at dehiscence. Subsequently, tissue samples from each tested suture position were evaluated for collagen content using a standard hydroxyproline assay. Among all mitral positions, no significant differences were detected among positions or regions with mean F_P values falling between 6.9 ± 2.6 N (posterior region) and 10.3 ± 4.7 N (anterior region). Among all tricuspid positions, the maximum F_P and minimum F_P were 24.0 ± 9.2 N (trigonal region) and 4.5 ± 2.6 N (anterior region). Although for the MV, a given sample's collagen content had no correlation to its corresponding F_P, the same relationship was significant for the TV. Further, the TV exhibited comparable F_P to the MV overall, despite a nearly 40% reduction in collagen content. These findings suggest that sutures placed in the trigonal region of the TV have higher pullout force than those placed along other segments of the annuli. Furthermore, there are likely differences in collagen orientation between the mitral and tricuspid annuli, such that collagen content strongly impacts F_P in one, but not the other.