Understanding the Mechanism of Tricuspid Annuloplasty Suture Dehiscence
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Functional tricuspid regurgitation is commonly repaired by ring annuloplasty. Suturing an annuloplasty ring into the tricuspid valve presents the potential for annular suture dehiscence (tear-out from the tissue) due to the cyclic forces applied by cardiac contraction. Dehiscence has been noted clinically across multiple studies examining TR repair by ring annuloplasty, primarily at the septal region of the annulus. Analysis of the tricuspid microstructure can support the development of improved implantation procedures to account for a potential lack of structural support in regions of the annulus. This study consists of 2 complimentary experiments aimed to understand the mechanism of suture dehiscence at the macro and micro levels. In the first, the tricuspid annulus suture holding strength was studied as a function of position. Tricuspid valves (N=15) were excised from ovine hearts and suture pullouts were conducted at 12 annular positions. In the second, relative collagen density at 6 suture passage sites around the annulus was quantified via autofluorescence microscopy, using a second cohort of valves (N=4). The highest pullout forces were experienced around the septal region of the annulus (e.g. septal leaflet vs. all other positions: 8.70 ± 3.14 N vs. 5.70 ± 1.94, p<0.0001), peaking at the middle of the septal leaflet (10.00 ± 4.07 N). This region also demonstrated the highest normalized collagen density, with a significant reduction at the anterior-posterior commissure, the posterior leaflet midpoint, and the posterior-septal commissure (each p<0.05 vs. septal leaflet). Taking this data together with the clinical predominance of dehiscence at the septal leaflet, it is believed that while a higher force is required to displace septal sutures, such higher forces must indeed occur in vivo. The ventricular septum is uniquely situated in a position that is subject to loading from both sides of the heart. The fibrous trigone present at the septum reduces the compliance of this region as a whole. Before these findings can be safely applied to inform novel ring designs or implantation practices, animal studies are necessary to discern how this dehiscence occurs in vivo.