Cracks in cryopreserved aortic allografts and rapid thawing.

Cryopreserved aortic allografts are shipped in a frozen state. Cracks in the graft, appearing after thawing, can pose serious problems in the planned operative procedures. Cracks were encountered in approximately 3% of all our shipped cryopreserved human material and were strongly associated with transportation in a "dry shipper." We practice two other modes of transport: on dry ice and directly to our operating room. We studied the temperature behavior during thawing of 17 porcine aortic valves in three groups. The valves were frozen and stored like our human valves. Before thawing, they were subjected to stimulated transport in either a dry shipper, on dry ice, or to the operating room. Differences between the groups were noted in the maximal rate of thawing of the inner as well as the outer wall. The highest maximal thawing rates were observed in the dry shipper group, in which 66% of the valves cracked. We therefore suspended transportation of cryopreserved human valves by means of a dry shipper.