Background. The injury resulting from postmortem ischemia is a critical deterrent to the availability of donor valves. Using the reduction of XTT- tetrazolium salt as a marker of metabolic sequelae, we assessed the injurious effect of ischemia and the metabolic sequelae in 156 porcine semilunar leaflets. Methods. The leaflets were randomly allocated to noncryoprocessed (n = 72) or cryoprocessed (n = 72) groups. At each preservation temperature of 4°C, 24 °C, or 37°C, 24 leaflets each were exposed to one of four storage periods of 9, 17, 30 or 60 hours. Twelve fresh aortic leaflets served as baseline reference samples. Results. There was a progressive loss in the metabolic functioning of valve leaflet cells in both noncryopreserved and cryopreserved tissue as the storage times increased. Cryopreserved tissue showed a greater loss of function than noncryopreserved tissue did. The metabolic injury was mainly a consequence of cryoprocessing. The greatest loss in metabolic functioning occurred in the valves stored for 60 hours. The least favorable combination of variables was cryopreservation and a precryopreservation storage time of 60 hours. Conclusions. We conclude that 30- to 60-hour delays do not have a significant metabolic effect on cardiac leaflets. Thus it may be possible to safely extend the permissible ischemic periods after organ harvest.
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