Hemodynamic evaluation of a bioprosthetic venous prosthesis

A prosthetic venous valve must be biocompatible and nonthrombogenic and function in the venous circulation. Biocompatibility and thrombogenicity of our prosthesis have been examined in prior animal experiments, and 91% of valve conduits including early prototypes are patent at 3 weeks. However, evaluation of valve function is much more difficult in animals; therefore in this study the function of excised valves was evaluated ex vivo.

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 human respiratory and hydrostatic variations. Each valve and conduit was tested for variations in valve diameter and sinus expansion in response to flow. Valve opening and closing times and valve competence were measured in response to pressure changes. After testing, each specimen was glutaraldehyde fixed and assessed a second time.

Valve orifice area increased in response to flow in both fresh and fixed tissues. Maximum valve orifice area was reduced by fixation (27.7%) at full flows (p < 0.05). Valve sinus dimensions increased in response to increased pressure until maximum expansion was achieved (33 mm Hg). This was 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 tissue (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.

Size and availability make the bovine jugular vein valve an ideal venous valve substitute. Glutaraldehyde fixation renders the tissue biocompatible and nonthrombogenic while preserving anatomic integrity and leaflet strength and flexibility. Mounted and stented in a sewing sleeve, this prosthesis could represent the first generally applicable clinical solution to chronic venous insufficiency and venous hypertension.