Long-term preservation of explanted hearts perfused with L-aspartate-enriched cardioplegic solution. Improved function, metabolism, and ultrastructure.

The effects of supplementing oxygenated St. Thomas' Hospital cardioplegic solution No. 2 with L-aspartate and/or D-glucose for the long-term preservation of excised rat hearts were determined with isolated working heart preparations. Left ventricular function was assessed at 37 degrees C with a crystalloid perfusate, before cardioplegic arrest and after 20 hours of low-flow perfusion (1.5 ml/min) with continuing arrest at 4 degrees C, and after this period, again at 37 degrees C with a crystalloid perfusate. Four groups (n = 8/group) of hearts were studied with four cardioplegic solutions: St. Thomas' Hospital solution alone, St. Thomas' Hospital solution with aspartate 20 mmol/L, St. Thomas' Hospital solution with glucose 20 mmol/L, and St. Thomas' Hospital solution plus both aspartate and glucose (20 mmol/L each). The addition of glucose to St. Thomas' Hospital solution made no significant difference in the recovery of aortic flow rates (17.7% +/- 8.6% and 21.6% +/- 7.8% of prearrest values), but when aspartate or aspartate and glucose were present, hearts showed significant improvements (89.8% +/- 5.2% and 85.0% +/- 6.2%, respectively). These improvements were associated with a reduction in the decline of myocardial high-energy phosphates during reperfusion, a reduction in cellular uptake of Na+ and Ca++, and a reduction in ultrastructural damage. These results indicate that low-flow perfusion with St. Thomas' Hospital solution plus aspartate can considerably extend the duration of safe storage of explanted hearts.