STUDIES IN A MODIFIED AUXILIARY ABDOMINAL RAT-HEART TRANSPLANTATION MODEL - PRESERVATION WITH COLLOID-FREE UNIVERSITY-OF-WISCONSIN SOLUTION

Background: Current clinical heart preservation is still limited to 6 hours. A suitable heart transplantation model to rapidly screen the ef fectiveness of new solutions is essential. This study examines a new s creening test-a modification of the conventional abdominal rat heart t ransplantation model that overcomes its serious limitation of lack of quantitative evaluation of function. Methods: Rat hearts, with an exte rnalized intraventricular balloon-tipped catheter, were transplanted i mmediately (controls) or flushed and stored in colloid-free University of Wisconsin solution in ice for 6, 9, or 12 hours before transplanta tion. One and 7 days later this catheter was connected to a pressure t ransducer and a calibrated syringe. Heart rate, maximum developed pres sure, and maximum rate of left ventricular pressure rise were determin ed. Grafts were prepared for histologic study on day 7. Results: All p reserved hearts commenced beating within 2 minutes (controls beat with in 20 seconds). On day 1 the heart rate and chamber stiffness (Delta P /Delta t) were similar in all groups. The 9- and 12-hour-preserved hea rts had significantly (p < 0.05) diminished developed pressure and con tractility. On day 7 contractility and developed pressure improved in 9- and 12-hour-preserved grafts. There was extensive muscular atrophy and necrosis, with extensive cellular infiltrate in the 9- and 12-hour -preserved grafts; other grafts showed no damage. Conclusion: This qua ntitative model provides an ischemia-related gradation of function and greater discrimination than conventional methods. It has refuted prev ious studies suggesting effective preservation for 20 hours and demons trated that functional testing is essential in evaluating preservation regimens.