Should the Aortic Valve Homograft Be Recryopreserved?

Background. The number of homograft donors is limited and the once-thawed homograft may be unsuitable for the recipient and obliged to be wasted. The purpose of this study was to investigate the possibility of recryopreserving and using the once-thawed homograft for another patient. Methods. Canine aortic valve leaflets were frozen to −80°C by a programmed freezer, stored in liquid nitrogen, and thawed after 1 week. A subgroup of leaflets was left at 4°C for 15 minutes, re-cryopreserved, and thawed after 1 week. Pathologic and flow cytometric evaluations were performed. Results. After thawing, by pathology, alignment of the fibers was acceptably maintained but the membrane and cytoplasm of the fibroblast were damaged. These findings were not significantly aggravated even after rethawing. By flow cytometry, fibroblast viability was 90.7% ± 1.7% immediately after thawing, 87.6% ± 1.0% after thawing for 15 minutes at 4°C, 63.7% ± 2.7% during refreezing at 0°C, and 39.4% ± 4.3% after rethawing. Conclusions. From the standpoint of fibroblast viability, it is not possible to recryopreserve the once-cryopreserved and thawed aortic valve homograft.