Influence of pre-existing ischemia on recovery from chemical cardioplegia. A study on pig hearts in an isolated blood-perfused model.

The impact of prior cardiac ischemia on recovery from chemical cardioplegia was investigated in pig hearts. Group I hearts were subjected to 9-min normothermic ischemia before the start of chemical cardioplegia. After 180 min of induced cardiac arrest, all hearts were reperfused and monitored for 120 min in a blood-perfused Langendorff model. Consistent with left ventricular performance, myocardial oxygen uptake was significantly lower in group I than in the other hearts during the first 60 min of reperfusion. Lactate elimination was significantly higher in group I at the start of reperfusion, but showed no intergroup difference after 25 min. Nor was intergroup difference found in left ventricular end-diastolic pressure, total myocardial flow or glucose extraction fraction during reperfusion. The mitochondrial ultrastructure was identical in the two groups before chemical cardioplegia. During cardioplegia it deteriorated in group I but normalized in group II. During reperfusion these circumstances were reversed. Although precardioplegic ischemia thus significantly impaired left ventricular performance during early recovery, with corresponding effects on metabolism and ultrastructure, stable performance during reperfusion indicated that the ischemic injury did not worsen.