Improved recovery of immature myocardium with l-glutamate blood cardioplegia

Enhancement of myocardial recovery with glutamate-enriched cold blood potassium cardioplegia (BPC) was evaluated using an isolated working heart model. Three groups of hearts from immature rabbits were subjected to 20 minutes of warm (37 °C) ischemia to allow energy depletion, followed by 90 minutes of hypothermic (10 °C) ischemia. Myocardial protection provided during hypothermia consisted of cardioplegia infusion, at 50 mm Hg every 30 minutes at 4 °C, of either St. Thomas' Hospital solution (group 1, n = 6), oxygenated BPC (group 2, n = 7), or oxygenated BPC enriched with 20 mmol/L l-glutamate (group 3, n = 7). Percent recovery of aortic flow was 87.6% ± 6.3% (results expressed as mean ± standard error of the mean) in group 3, which was significantly better than for either group 1 (63.4% ± 4.0%) or group 2 (47.0% ± 3.5%) (p < 0.05 by analysis of variance). Group 3 hearts had significantly better recovery of myocardial energy stores (μmol/g dry weight) compared with group 1 or 2 hearts: adenosine triphosphate, 17.8 ± 1.1 versus 12.4 ± 1.5 and 12.1 ± 0.4; creatine phosphate, 25.9 ± 1.8 versus 17.8 ± 1.8 and 20.3 ± 0.7; and glycogen, 140.7 ±12.6 versus 98.7 ± 9.9 and 60.7 ± 9.9 (p < 0.05). Glutamate-enriched BPC provided excellent myocardial protection after ischemia in this immature model, and this study quantitatively supports the use of glutamate-enriched BPC in neonatal clinical practice.