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 (R2 = 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.

Novel Method to Track Soft Tissue Deformation by Micro-Computed Tomography: Application to the Mitral Valve.

Increasing availability of micro-computed tomography (µCT) as a structural imaging gold-standard is bringing unprecedented geometric detail to soft tissue modeling. However, the utility of these advances is severely hindered without analogous enhancement to the associated kinematic detail. To this end, labeling and following discrete points on a tissue across various deformation states is a well-established approach. Still, existing techniques suffer limitations when applied to complex geometries and large deformations and strains. Therefore, we herein developed a non-destructive system for applying fiducial markers (minimum diameter: 500 µm) to soft tissue and tracking them through multiple loading conditions by µCT. Using a novel applicator to minimize adhesive usage, four distinct marker materials were resolvable from both tissue and one another, without image artifacts. No impact on tissue stiffness was observed. µCT addressed accuracy limitations of stereophotogrammetry (inter-method positional error 1.2 ± 0.3 mm, given marker diameter 1.9 ± 0.1 mm). Marker application to ovine mitral valves revealed leaflet Almansi areal strains (45 ± 4%) closely matching literature values, and provided radiographic access to previously inaccessible regions, such as the leaflet coaptation zone. This system may meaningfully support mechanical characterization of numerous tissues or biomaterials, as well as tissue-device interaction studies for regulatory standards purposes.