HEMODYNAMIC EVALUATION OF A BIOPROSTHETIC VENOUS PROSTHESIS

Purpose: A prosthetic venous valve must be biocompatible and nonthromb ogneic and function in the venous circulation. Biocompatibility and th rombogenicity of our prosthesis have been examined in prior animal exp eriments, and 91% of valve conduits including early prototypes are pat ent at 3 weeks. However, evaluation of valve function is much more dif ficult in animals; therefore in this study the function of excised val ves was evaluated ex vivo. Methods: Nine bovine jugular vein conduits, each with one bileaflet venous valve, were harvested and placed in a venous flow simulator. Flows and pressures were adjusted to mimic huma n respiratory and hydrostatic variations. Each valve and conduit was t ested for variations in valve diameter and sinus expansion in response to flow. Valve opening and closing times and valve competence were me asured in response to pressure changes. After testing, each specimen w as glutaraldehyde fixed and assessed a second time. Results: Valve ori fice area increased in response to flow in both fresh and fixed tissue s. Maximum valve orifice area was reduced by fixation (27.7%) at full flows (p < 0.05). Valve sinus dimensions increased in response to incr eased pressure until maximum expansion was achieved (33 mm Hg). This w as reduced 15.3% in fixed tissue (p < 0.05). Valve opening times (at < 1 mm Hg gradient) were slightly longer in fixed compared with fresh t issue (0.43 +/- 0.09 vs 0.41 +/- 0.13 second; p < 0.05). Valve closing times were comparable in both states (0.43 +/- 0.08 vs 0.49 +/- 0.07 second). Three fresh and seven fixed specimens that were subjected to 287 mm Hg back pressure exhibited minimal reflux. Conclusions: Size an d availability make the bovine jugular vein valve an ideal venous valv e substitute. Glutaraldehyde fixation renders the tissue biocompatible and nonthrombogenic while preserving anatomic integrity and leaflet s trength and flexibility. Mounted and stented in a sewing sleeve, this prosthesis could represent the first generally applicable clinical sol ution to chronic venous insufficiency and venous hypertension.