Suture Dehiscence in the Tricuspid Annulus: An Ex Vivo Analysis of Tissue Strength and Composition

Background Surgical repair of functional tricuspid regurgitation (FTR) is an increasingly common practice, but annuloplasty suture dehiscence remains a significant problem. Quantitative and mechanistic understanding of annular suture holding strength can support more effective techniques for tricuspid valve device anchoring. Methods Suture holding strength of ovine tricuspid annuli (n = 15) was quantified ex vivo by pullout testing at 12 positions around their circumference. Collagen density in additional annuli (n = 7) was quantified at positions above each commissure and midleaflet point by two-photon autofluorescence microscopy, enabling mechanistic assessment of its role in imparting suture holding strength to the tissue. Results Suture holding strength from pullout testing varied significantly by annular position, with a maximum of 10.0 ± 4.1 N at the septal leaflet (6 o'clock) and a minimum of 4.3 ± 1.3 N at the posterior leaflet (1 o'clock). Leaflet midpoints showed significantly higher annular tissue strength than commissures (7.2 ± 3.4 N versus 5.6 ± 2.1 N, respectively, p  = 0.008). Collagen density, measured by a normalized mean pixel intensity, was significantly higher in the septal annulus than in the posterior-septal commissure, posterior annulus, and anterior-posterior commissure. Suture holding strength showed a strong linear correlation with collagen density (R 2  = 0.822, p  = 0.013). Conclusions The clinical predominance of suture dehiscence at the septal annulus, despite its greater ex vivo holding strength, suggests either adverse suture placement techniques in this region or asymmetric tensile loading after implantation. This issue highlights the need to optimize implantation techniques and to carefully assess anchor security in existing and next-generation FTR corrective devices.