CONTRACTILE AND VASCULAR CONSEQUENCES OF BLOOD VERSUS CRYSTALLOID CARDIOPLEGIA IN THE ISOLATED BLOOD-PERFUSED RAT-HEART

The protective effects of sanguineous and asanguineous St. Thomas' cardioplegia (SCP and ACP) on postischemic vasodilator responsiveness, left ventricular developed pressure and end-diastolic pressure (LVDP and LVEDP), tissue adenosine triphosphate (ATP) and creatine phosphate (CP) contents were compared in the isolated blood-perfused rat heart. Five groups of hearts were studied: the controls (n = 8) perfused with blood (from a support rat) for 50 min (37-degrees-C), versus hearts (n = 14/group) arrested by a single infusion of either cardioplegic solution (15-degrees-C) prior to global ischemia (15-degrees-C) and blood reperfusion (37-degrees-C). After 2 or 4 h of ischemia and 50 min of reperfusion, endothelium-dependent vasodilator acetylcholine (1 mug) induced a 10 +/- 0.5 and 8.5 +/- 0.5% reduction, respectively, in coronary resistance, in the SCP groups, but only a 6.5 +/- 0.6 and 4.5 +/- 0.5% reduction (P < 0.05), respectively, in the ACP groups. However, there were no significant differences in LVDP, LVEDP, tissue ATP and CP contents, and endothelium-independent vasodilator response to nitroglycerin between the two cardioplegic groups. In a further study, rat hearts (n = 8/group) were arrested with SCP (magnesium concentration < 0.5, 5.0 or 16.0 mmol/l, in groups 1, 2 and 3) and subjected to 4 h of global ischemia (15-degrees-C) followed by 50 min of blood reperfusion (37-degrees-C). At the end of reperfusion, LVDP (at a ventricular volume of 180 mul) was 60 +/- 3.4, 72 +/- 3.5 and 70 +/- 3.2 in groups 1, 2 and 3, respectively. There were no significant differences in LVEDP or tissue ATP and CP contents. In conclusion: (1) SCP provided better preservation of endothelium-dependent vasodilator response than ACP; (2) the two cardioplegic solutions achieved comparable preservation of contractile function, ATP and CP contents; and (3) added magnesium enhanced the protective properties of SC P with regard to contractile function.