Optimal storage period for extended heart preservation with the University of Wisconsin Solution. A study of the left ventricular pressure-volume relationship.

To define the optimal and safe storage period in the use of the University of Wisconsin Solution (UWS) for extended heart preservation, 34 adult canine hearts were preserved under static and hypothermic conditions for 6, 12, 18, and 24 hours. A group of 10 hearts were used as a control of the preparation used in the study. Left ventricular functions were assessed in an isolated heart preparation equipped with a computerized servo-pump to measure the pressure-volume relationship. The systolic, diastolic and total ventricular performance were derived from the end-systolic pressure-volume relationship, end diastolic pressure-volume pressure relationship, and the stroke work-end diastolic volume relationship, respectively. Myocardial water content and coronary resistance during reperfusion were also analyzed. The study revealed that UWS was able to maintain normal levels of systolic and diastolic functions, and consequently normal level of total ventricular performance after 6 hours of storage. There was a reduction of diastolic function while the systolic function was still well maintained after 12 hours of preservation. The results after 12 hours were poor. There was no increase in the myocardial water content for up to 24 hours of storage; however, the coronary resistance during reperfusion significantly increased in the 18-hour group and the 24-hour group. The findings suggest that UWS may extend the safe period of myocardial preservation beyond the traditional 4 hours of storage closer to 12 hours of storage.