EFFECT OF CRYSTALLOID CARDIOPLEGIC SOLUTION AT DIFFERENT CALCIUM-CONCENTRATION ON IMMATURE MYOCARDIUM

Objective To determine the myocardial protective effect of crystalloid cardioplegic solution at different calcium concentration on immature myocardium. Methods Isolated perfused neonatal rabbit hearts from thre e groups, arrested by intermittent infusion of St. Thomas II cardiople gic solution with different concentration of calcium tin each group, o nly calcium concentration of cardioplegic solution was modified, I.[Ca 2+]0.6 mmol/L; II.[Ca2+]1.2 mmol/L; III. [Ca2+]2.4 mmol/L), were kept ischemic globally at 20 degrees C for 90 minutes and then followed by 30 minutes of reperfusion in Langendorff mode. Results Although the re covery of LVDP, + dp/dt(max) at calcium content of 2. 4 mmol/L after 1 0 minutes of reperfusion was significantly higher than those at 0.6 an d 1.2 mmol/L calcium (P < 0.05, P < 0.01, respectively). The declined tendency of left ventricular hemodynamics after 20 minutes of reperfus ion in this group was detected. By the end of reperfusion, the left ve ntricular functional recovery at 2.4 mmol/L calcium did not differ fro m those at 1.2 and 0.6 mmol/L calcium. Conversely, postischemic left v entricular functions at 0. 6 and 1.2 mmol/L calcium were gradually imp roved during 30 minutes of reperfusion. In 2.4 mmol/L calcium group, t he Ca2+-ATPase activity significantly increased(P < 0.01, P < 0.001) w hereas myocardial ATP content was lower when compared with 1. 2 mmol/L (P < 0. 001) and 0. 6 mmol/L calcium groups. Conclusions Our research demonstrated that there were no statistical differences with respect to hemodynamic recovery in three groups after 30 minutes of reperfusio n although left ventricular functional recovery at 2.4 mmol/L calcium accelerated early after reperfusion. In addition, with 2.4 mmol/L calc ium, myocardial ATP content was decreased significantly. We conclude t hat, from the point of view of myocardial energy metabolism, St. Thoma s II cardioplegic solution at high concentration of calcium can not pr ovide immature myocardium with optimal myocardial protection while wit h 1.2 mmol/L calcium, however, better high-energy store can be preserv ed.