Blood cardioplegia for cardiac surgery in acute myocardial infarction: rat experiments with two widely used solutions.

Abstract

Blood cardioplegia (BCP) can be used in different ways to protect the heart from ischaemia-reperfusion injury during cardiac surgery. Because there could be differences between warm and cold intermittent cardioplegia with or without warm reperfusion, we investigated the influence of 2 blood cardioplegia solutions on cardiac function, metabolism and infarct size in stable and infarcted rat hearts. The hearts of 32 male Wistar rats were excised and inserted into a blood-perfused isolated heart apparatus. In 16 hearts, an acute myocardial infarction was induced by ligation of the left anterior descending coronary artery at least 30 min before aortic clamping. After aortic clamping, either Calafiore or Buckberg BCP was administered. During reperfusion, coronary blood flow, left ventricular developed pressure and dp/dt max were recorded, and oxygen consumption and lactate production were determined. The infarct size after 90 min of reperfusion was measured by triphenyl tetrazolium chloride staining. The hearts of rats without infarction were investigated using transmission electron microscopy. In hearts without infarction, haemodynamic recovery was similar for Calafiore and Buckberg solutions: left ventricular developed pressure [Cala 62% of baseline (BL), Buck 58% BL] and dp/dt max (Cala 83% BL, Buck 89% BL). Coronary flow, which was slightly less in infarcted hearts, also recovered similarly after the administration of the 2 BCP solutions (Cala 65% BL, Buck 68% BL). During reperfusion, lactate production was similar (Cala 0.85 ml/min, Buck 1.0 ml/min), and the cellular oedema index and mitochondrial swelling were comparable between the 2 groups. In hearts with infarction, left ventricular developed pressure (Cala 58% BL, Buck 56% BL) and dp/dt max (Cala 79% BL, Buck 72% BL) showed similar recovery for reperfusion with Calafiore or Buckberg BCP. In addition, coronary flow recovered similarly (Cala 54% BL, Buck 57% BL). During reperfusion, myocardial oxygen consumption was lower in the Cala (67% BL) than in the Buck (82% BL) group, but lactate production was similar between the Cala (1.1 ml/min) and the Buck (1.1 ml/min) groups. Myocardial infarct size was also similar in the Cala group (24%) and in the Buck group (26%). In stable perfused rat hearts and in an in vitro model of acute myocardial infarction, the 2 BCP solutions offer equally good myocardial protection.