Abstract Body (Do not enter title and authors here): Background: Cold static storage of the heart in ice for transportation is thought to cause post-transplantation graft dysfunction secondary to freeze injury. No basic science or randomized clinical trial has objectively evaluated this concern.
Hypothesis: Hearts stored at 0°C for four hours do not sustain freeze injury.
Aim: To quantify the myocardial damage and resulting function in hearts stored at 0^oC, 4^oC and 8^oC for four hours.
Methods: Male Sprague-Dawley rat hearts were procured under general anesthesia and immediately stored in University of Wisconsin solution at 0^oC, 4^oC and 8^oC for four hours (n = 6-8/group). Hearts were then re-perfused on a Langendorff apparatus for 90 minutes using oxygenated Krebs-Henseleit buffer (37^oC) at a perfusion pressure of 73 mmHg. Functional parameters were recorded via a balloon tip catheter in the left ventricle. Coronary flow rate was monitored with timed collection of effluent. At the end, hearts were collected for infarct size quantification using triphenyltetrazolium chloride staining.
Results: Infarct size in hearts stored at 0°C, 4°C, and 8°C were 28±1%, 32±2%, and 39.7±2%, respectively. There was no significant difference in infarct size between hearts stored at 0°C and 4°C. Hearts stored at 8°C had a significantly larger infarct size compared to both 0°C and 4°C (P = 0.0004 and 0.0178, respectively). Left ventricle developed pressure in hearts stored at 0°C, 4°C, and 8°C were 55±4 mmHg, 51±3 mmHg, and 55±2 mmHg, respectively (all P > 0.05). Negative dP/dt in hearts stored at 0°C, 4°C, and 8°C were -2505±274 mmHg/sec, -1969±186 mmHg/sec, and -1861±175 mmHg/sec, respectively (all P > 0.05). Coronary flow at 4°C (22 mL/min) was higher compared to 0°C (19 mL/min) and 8°C (16 mL/min) (P=0.0371 and P=0.0003, respectively). Cardiac troponin I levels in the coronary effluent from hearts stored at 0°C, 4°C, and 8°C were 0.88±0.1 ng/ml, 0.86±0.1 ng/ml, and 1.24±0.2 ng/ml, respectively (all P > 0.05).
Conclusion: Hearts stored at 0°C for four hours showed no signs of freezing, they showed similar functional parameters and comparable levels of biochemical markers for injury compared to hearts stored at 4°C. Hearts stored at 8°C had a larger infarct size compared to 0°C or 4°C.