Minimally immunogenic decellularized porcine valve provides in situ recellularization as a stentless bioprosthetic valve.

Currently used bioprosthetic valves have several limitations such as calcification and functional deterioration, and revitalization through cellular ingrowth is impossible. To overcome these obstacles, we have developed a minimally immunogenic tissue-engineered valve that consists of an unfixed, decellularized porcine valve scaffold capable of being spontaneously revitalized in vivo after implantation. Porcine aortic root tissue was decellularized using detergents such as sodium lauryl sulfate and Triton X-100. The porcine valve was treated very gently and plenty of time was allowed for constituents to diffuse in and out of the matrix. In a preliminary study, a piece of decellularized porcine valve tissue was implanted into the rat subdermal space for 14 and 60 days and the structural integrity and calcification were evaluated. As an in vivo valve replacement model, the decellularized porcine valve was implanted in the pulmonary valve position in dogs and functional and histological evaluation was performed after 1, 2, and 6 months. Histological examination showed that the newly developed detergent treatment effectively removed cellular debris from the porcine aortic tissue. Decellularized porcine valve tissue implanted subdermally in rats showed minimal inflammatory cell infiltration and calcification. In the valve replacement model, spontaneous reendothelialization and repopulation of the medial cells were observed within 2 months, and good valve function without regurgitation was observed by echocardiography up to 6 months. The minimally immunogenic decellularized porcine valve proved effective in mitigating postimplant calcification and provided a suitable matrix for revitalizing prostheses through in situ recellularization, cellular ingrowth, and tissue remodeling.

Flow characterization of the ADVANTAGE and St. Jude Medical bileaflet mechanical heart valves.

BACKGROUND AND AIM OF THE STUDY: The study aim was to characterize time-dependent flow fields and flow structures within the ADVANTAGE (ADV) and St. Jude Medical (SJM) prosthetic bileaflet mechanical heart valves. METHODS: Three-dimensional unsteady computational fluid dynamic simulations were conducted in the aortic position for both valves. Flow boundary conditions were acquired from an in-vitro experiment. The governing equations were solved by a finite volume method that employed a moving cell technique to simulate the motion of the valve leaflet in the cardiac cycle. The computed velocities were subsequently validated using the velocities measured in the in-vitro experiment. RESULTS: Both valves had similar flow phenomena at the geometric symmetry plane of the valve housing, and both experienced a waterhammer effect upon closure. However, flow characteristics in the pivots differed distinctively between both valves. More dynamic flow activity was observed at the bi-level butterfly pivots of the ADV valve. Flow vena contracta and large flow boundary separation zones at the central flow orifice were captured adjacent to the pivots of the SJM valve. During valve opening, retrograde systolic flow at the bottom of the pivot was observed. No persistent flow stases were seen in the pivots of either valves. CONCLUSION: Although overall flow characterization for both valves was similar, flow features within each valve's pivots correlated to the pivot design. The bi-level butterfly pivot design of the ADV valve appeared to provide relatively easy passages for pivot flow washing.