Mitochondrial dehydrogenase depletion in leaflet matrix cells during processing of cryopreserved cardiac valves

Background. Cryopreserved cardiac valves in homograft have been clinically used for the past 35 years. Because of the shortage of donors, method of preservation and ischemia time-interval allowed have become critical steps in precryoprocessing. The injurous effects of preservation time and temperature of cardiac valves with and without cryopreservations have been studied. Methods. From 26 pigs, 156 semilunar leaflets were randomly divided into cryo- (n=78) and noncryo- (n=78) processed groups and harvested. For each preserving temperature of 4°C, 24°C, and 37°C, the leaflets were kept ischemically for 0, 9, 17, 30, and 60 hours, respectively. The metabolic injury to cardiac valves was determined by mitochondrial dehydrogenase (MD) activity. Results. The noncryoprocessed group retained about 75% activity of MD at 4 °C and 24 °C over a period of 60 hours. In the cryoprocessed group, the depletion of MD activity was more severe than for the non-cryoprocessed at all temperature tested. To maintain more than 50% of MD activity after cryoprocessing, short-term storage should be limited to 24 °C within 60 hours, 4°C in 30 hours or 37°C in 15 hours (p<0.01). Less than 20% activity of MD was found at 37°C for 60 hours. Discussion. The results showed the significant influence of storage temperature on MD activity. Storage time interval is one of the critical factors in causing a steady loss of viability. When semilunar valves were maintained at 4°C or 24°C, only minimal depletion of MD activity occurred under such 'cadaveric' ischemia.