Integrity and viability of homograft valves.

Since it has been suggested that the leaflet tissue viability influences durability after homologous valve replacement, we compared different harvest and preservation techniques in order to examine the quality and smoothness of homograft conservation. We analyzed human aortic and pulmonary valve leaflets obtained from 'heart-beating donors' (HBD) during heart transplantation and from 'non-heart-beating donors' (NHBD) during coroner's autopsies. Valves were either cryopreserved in liquid nitrogen or stored at 4 degrees C in nutrient medium similar to the procedure reported in our protocols of the homograft bank system. All grafts from NHBD had been antibiotically sterilized for 3 days beforehand. Morphological observations were made using light and electron microscopy and, in order to characterize the endothelial cell viability, a non-radioactive cell proliferation assay was used. The PGI2 secretion of the remaining endothelium was defined as the 6-keto-prostaglandin F1 alpha metabolite by an enzyme immunoassay. Observations in the scanning electron microscope revealed that, after cryopreservation, homografts show an almost confluent endothelium when processed within 24 h after harvest from HBD, but lack endothelial cells when obtained from NHBD. Cryopreserved grafts from NHBD exhibited an altered tissue structure with edema and vacuolization within the spongiosa of the leaflets as well as irreversible cell damage when examined under the light and transmission electron microscope. That the metabolic activity of HBD homografts was maintained was confirmed by proven PGI2 secretion (6150 +/- 1200 pg/3 ml M199 after cryopreservation), whereas specimens from NHBD showed a reduced (1950 +/- 730 pg/3 ml M199) and, after cryopreservation, almost no release (P < 0.0001).(ABSTRACT TRUNCATED AT 250 WORDS)