Objective To determine the myocardial protective effect of St.Thomas Ⅱ
cardioplegia at different calcium
concentration on
immature myocardium. Methods Isolated perfused neonatal rabbit hearts from three groups (the calcium
concentration of St.Thomas Ⅱ
cardioplegia was modified:
0.6 mmol/L; 1.2 mmol/L; 2.4 mmol/L) were subjected to 20℃ hypothermia, 90 minutes of global ischemia followed by 30 minutes reperfusion in Langendorff mode. Results Although the recovery of LVDP, ±dp/dt max at calcium content of 2.4 mmol/L after 10 minutes of reperfusion was significantly higher than that at 0 6 and 1.2 mmol/L calcium ( P <0.05, P <0.01, respectively), the declined tendency of left ventricular hemodynamics in this group was detected after 20 minutes of reperfusion. By the end of 30 minute reperfusion, the left ventricular hemodynamic recovery at 2.4 mmol/L calcium did not differ from those at 0.6 mmol/L and 1.2 mmol/L calcium. Conversely, postischemic left ventricular functions at 0.6 and 1.2 mmol/L calcium were gradually improved during the 30 minutes reperfusion. Ca 2+ ATPase activity at 2.4 mmol/L calcium showed significant increase ( P <0.01, P <0.001), whereas ATP content was lower than that of other groups. Conclusion Calciun accumulated in extracellular space during ischemia enters myocardial cell via Ca 2+ channel and Ca 2+ /Na + exchange after reperfusion, activates Ca 2+ ATPase, and finally accelerates adenosinetriphosphate (ATP) consumption induced by calcium, which would be responsible for the results of our study. We conclude that, from the point of view of myocardial cell energy metabolism, St. Thomas Ⅱ cardioplegia at high calcium concentration can not provide immature myocardium with optimal myocardial protection.