Integrity and viability of homograft valves

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Abstract
Since it has been suggested that the leaflet tissue viability influencesdurability after homologous valve replacement, we compared differentharvest and preservation techniques in order to examine the quality andsmoothness of homograft conservation. We analyzed human aortic andpulmonary valve leaflets obtained from 'heart-beating donors' (HBD) duringheart transplantation and from 'non-heart-beating donors' (NHBD) duringcoroner's autopsies. Valves were either cryopreserved in liquid nitrogen orstored at 4 degrees C in nutrient medium similar to the procedure reportedin our protocols of the homograft bank system. All grafts from NHBD hadbeen antibiotically sterilized for 3 days beforehand. Morphologicalobservations were made using light and electron microscopy and, in order tocharacterize the endothelial cell viability, a non-radioactive cellproliferation assay was used. The PGI2 secretion of the remainingendothelium was defined as the 6-keto-prostaglandin F1 alpha metabolite byan enzyme immunoassay. Observations in the scanning electron microscoperevealed that, after cryopreservation, homografts show an almost confluentendothelium when processed within 24 h after harvest from HBD, but lackendothelial cells when obtained from NHBD. Cryopreserved grafts from NHBDexhibited an altered tissue structure with edema and vacuolization withinthe spongiosa of the leaflets as well as irreversible cell damage whenexamined under the light and transmission electron microscope. That themetabolic activity of HBD homografts was maintained was confirmed by provenPGI2 secretion (6150 +/- 1200 pg/3 ml M199 after cryopreservation), whereasspecimens from NHBD showed a reduced (1950 +/- 730 pg/3 ml M199) and, aftercryopreservation, almost no release (P < 0.0001).(ABSTRACT TRUNCATED AT250 WORDS)

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