The Cryopreserved Stented Pulmonary Homograft Valve in the Tricuspid Position

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Abstract
This study was designed to evaluate the early phase events occurring in a stented pulmonary homograft valve implanted in the tricuspid position. A human pulmonary homograft was sterilized in antibiotic solution for 48 hours and cryopreserved in liquid nitrogen (–176°C). Following thawing and trimming, the pulmonary valve was mounted on a Dacron cloth‐covered Delrin stent and implanted into the tricuspid position in 3‐month‐old sheep, for a mean of 95 ± 5 days. Seven animals were studied. Morphological assessment indicated good structural tissue preservation despite a decrease in viable fibroblasts noted in the distal part of the leaflets. The collagen fibers remained unchanged, and no tissue calcification was found. Viability of the mounted homograft was evaluated using an in vitro tissue culture method, and the viable cells underwent chromosomal analysis to identify whether they originated from the donor or host. Cells with 56 chromosomes, a number intrinsic to sheep cells, were cultured from the donor‐recipient junctional area. Hemodynamic and angiographic data, which were collected at the time of both implantation and explantation, revealed no functional deterioration of the implanted valve over 3 months. At the time of explantation, six of the seven valves were competent and no cusp retraction or thickening was noted. The seventh valve had deteriorated due to endocarditis. We conclude that stented cryopreserved pulmonary homografts may be useful as bioprostheses in the tricuspid position.