How Local Annular Force and Collagen Density Govern Mitral Annuloplasty Ring Dehiscence Risk

Background Annuloplasty ring dehiscence is a well described mode of mitral valve repair failure. Defining the mechanisms underlying dehiscence may facilitate its prevention. Methods Factors that govern suture dehiscence were examined with an ovine model. After undersized ring annuloplasty in live animals (n = 5), cyclic force (FC ) that acts on sutures during cardiac contraction was measured with custom transducers. FC was measured at ten suture positions, throughout cardiac cycles with peak left ventricular pressure (LVPmax ) of 100, 125, and 150 mm Hg. Suture pullout testing was conducted on explanted mitral annuli (n = 12) to determine suture holding strength at each position. Finally, relative collagen density differences at suture sites around the annulus were assessed by two-photon excitation fluoroscopy. Results Anterior FC exceeded posterior FC at each LVPmax (eg, 2.8 ± 1.3 N versus 1.8 ± 1.2 N at LVPmax = 125 mm Hg, p < 0.01). Anterior holding strength exceeded posterior holding strength (6.4 ± 3.6 N versus 3.9 ± 1.6 N, p