Systolic and diastolic properties and myocardial blood flow in the heterotopically transplanted rat heart during acute cardiac rejection

The aim of the study was to characterize the course of systolic and diastol ic function, myocardial blood flow, and histologic changes during acute rej ection in a model of heterotopic transplantation in rats. For this purpose isogenic Lewis-to-Lewis and allogenic DA (Dark Agouti)to-Lewis rat cardiac transplants were studied 1 hour and 1, 3, and 5 days, respectively, after h eterotopic intraabdominal transplantation. Myocardial tissue blood flow (MB F) was assessed by the hydrogen-clearance method. An implanted balloon was used to measure pressure-volume relations in the transplanted heart. Myocar dial water content was determined at the end of the experiments, and histol ogic examinations were performed. The MBF recovered during the first day po stoperatively in both groups and decreased again in the allogenic group aft er 3 and 5 days (p < 0.05); it remained stable in the isogenic group. Myoca rdial relaxation was already prolonged in the allogenic group after 3 days and deteriorated further. Left ventricular end-diastolic pressure progressi vely increased in the allogenic group, whereas it remained unchanged in the isogenic group up to 5 days. lifter recovery from ischemia, the left ventr icular peak systolic pressure was stable in the isogenic group for the enti re further observation period, but it significantly decreased in the alloge nic group after 5 days (p < 0.05), Myocardial water content showed a signif icant increase in the allogenic group compared to that in the isogenic grou p after 5 days. In the allogenic group histologic examination confirmed mil d to moderate rejection after 3 days and severe acute rejection after 5 day s, Thus, after recovery from ischemia, mild to moderate cardiac rejection w as associated with reduced MBF and impaired relaxation, In a typical sequen ce, generation of edema and impaired diastolic compliance were terminally f ollowed by systolic dysfunction during severe rejection.