EFFECT OF IMPROVED MYOCARDIAL PROTECTION ON EDEMA AND DIASTOLIC PROPERTIES OF THE RAT LEFT-VENTRICLE DURING ACUTE ALLOGRAFT-REJECTION

Background: Studies of myocardial edema and diastolic dysfunction in r at heart transplantation have been flawed by ischemic injury. This stu dy uses improved methods to prevent ischemic contracture. Methods: Hea rts of 30 ACI rats were transplanted into the abdomen of Lewis rats by use of cold University of Wisconsin solution for improved preservatio n. Left ventricular diastolic properties were expressed as volume at s tandardized pressure intervals. Results: On posttransplantation day 3, mean left ventricular volume at 15 mm Hg in allografts (290 +/- 9 mu l, SEM) was not significantly different vs isografts (299 +/- 32 mu l) , allografts on day 0 (337 +/- 28 ml) or day 1 (324 +/- 20 mu l), or n ative hearts (334 +/- 19 mu l) However, volume was reduced to 173 +/- 17 mu l on day 4 and to 70 +/- 23 mu l on day 5 (p < 0.05). Similar fi ndings were obtained for volume at 5 and 10 mm Hg. Allograft myocardia l water content on day 3, 76.3% +/- 5%, similar to allografts on day 0 and 1 and to isografts on day 3, increased to 77.6% +/- 8% on day 4 ( NS) and 79.4% +/- 6% on day 5 (p < 0.05 vs day 0). Histologically, rej ection in allografts was mild on day 3, moderate on day 4, and severe on day 5. Conclusions: Reduced left ventricular filling volume during rejection is only partially explained by edema. Abnormalities of diast olic properties previously attributed to the unloaded state of nonwork ing heart models may actually reflect inadequate peritransplantation m yocardial protection.