Increased temperature reduces the protective effect of University of Wisconsin solution in the heart

Background. The protective effect of University of Wisconsin solution (UW) for hypothermic storage of donor hearts has been demonstrated in the laboratory. However, clinical usage is associated with occasional primary graft failures. We postulated that this could be related to adverse effects of UW on the coronary vasculature during cardiac implantation and rewarming. We therefore assessed recovery of contractile function and coronary flow in rat hearts after cardioplegic arrest using UW compared with St. Thomas’ solution (ST) at 4°C or 25°C. Methods. Cardioplegia was induced in isolated rat hearts using either UW or ST at 4°C. Hearts were then maintained at 4°C or 25°C. In some hearts, UW at 4°C was used for inducing arrest followed by flushing with ST at 4°C and then rewarming to 25°C. After 40 minutes of arrest, recovery of function and coronary flow were measured. Nuclear track emulsion was used to assess microvascular competence. Results. Compared with ST–treated hearts, UW–treated hearts showed significant reduction in recovery of function at 25°C (76.2% ± 4.0% versus 25.0% ± 4.1%; p< 0.01) but not at 4°C (88.0% ± 1.6% versus 87.1% ± 2.6%). Recovery of coronary flow in the UW–treated hearts at 25°C was significantly lower than that in the ST–treated hearts at 25°C (71.7% ± 3.0% versus 94.5% ± 6.3%; p< 0.01). At 25°C, microvascular competence was reduced in the UW group compared with the ST group. At 25°C, flushing out UW with ST resulted in greater recovery of function compared with UW throughout (73.4% ± 7.1% versus 25.0% ± 4.1%; p< 0.01). Conclusions. University of Wisconsin solution provides effective donor heart protection under hypothermic conditions but can be deleterious at warmer temperatures.