Effect of warm ischemia and cryopreservation on cell viability of human allograft valves

Fibroblast viability of the allograft valve leaflet has been suggested to affect clinical durability. Warm ischemic time is thought to be one of the critical determinants of cell viability. We assessed cell viability of allograft valves by flow cytometry, using a fluorescein diacetatepropidium iodide stain to characterize the effects of warm ischemia and cryopreservation on viability. Twelve human pulmonary valves with harvest-related warm ischemic times (range, 70 to 520 minutes; mean ± standard deviation, 225 ± 157 minutes) were studied by flow cytometry. We assessed cell viability of the allograft valve leaflets before and 30 days after storage. A significant negative correlation was found between warm ischemic time (x minutes) and cell viability (y%) before (y = -0.024x + 96.7; r2 = 0.62; p = 0.002) and after 30 days of storage (y = -0.036x + 94.0; r2 = 0.86; p = 0.001). Cell viability of the cryopreserved allograft valves was well preserved (>70%) with a warm ischcmic time less than 520 minutes (8.7 hours).