Isograft studies were performed in the murine model of
cardiac transplantation to investigate the morphologic effects of operative
ischemia. Primarily vascularized CBA mouse hearts were grafted heterotopically into the recipient CBA mouse's abdomen with standard microsurgical techniques. After
ischemia times of 30 and 60 minutes, histologic examination showed minimal myocardial damage, with
necrosis or
scarring occupying less than 5% of the cross-sectional area of hearts bisected from apex to base after grafts had been removed on the seventh day after
transplantation. Maximal ischemic damage was seen at 7 days after
transplantation after 120 minutes of
ischemia, with more than 30% myocardial
necrosis or
scarring of myocardial tissue. Isografts performed with
ischemia times of less than 60 minutes were followed for more than 100 days. All hearts showed a fine, generalized, perimyocytic
fibrosis, which was maximal at 28 days after
transplantation and did not progress thereafter. These results will serve as important control measures for future studies in this model because ischemic damage must be considered in examining histologic samples from long-surviving cardiac allografts maintained in immunosuppressed recipients.