The hybrid xenograft/autograft bioprosthetic heart valve: In vivo evaluation of tissue extraction

The major functional problem with bioprostheses is poor long-term durability. Bioprosthetic valves fail because of calcification and mechanical fatigue, both of which result from the glutaraldehyde fixation process. In an effort to develop a biologically active, non-cross-linked bioprosthetic valve, we devised a cellular extraction process. We tested the mechanical integrity of the processed valves and cultured both human and porcine cells on this material. To test the potential for calcification, we implanted strips of fresh, extracted, and glutaraldehydetreated porcine heart valve tissue subcutaneously into 3-week-old Sprague Dawley rats for 21 days. We used atomic absorption spectroscopy to measure the extent of calcium accumulation and histopathologic assessment to evaluate the antigenic response. We found that the cell extraction process significantly reduced the propensity of the material to calcify in vivo (mean ±standard deviation, 4.12 ±1.02 mg/g calcium extracted versus 10.75 ±3.9 mg/g calcium fresh versus 79.6 ±18.3 mg/g calcium glutaraldehyde fixed) but increased the antigencity, as evidenced by increased cellular activity and resorption. Although they may reduce calcification, conventional detergent-based cell extraction techniques do not completely remove porcine aortic valve antigens and may in fact increase the antigenicity of the valve cusp material.