Myocardial metabolism during aortic valve replacement. II. Bolus infusion of cold blood for cardioplegia

Myocardial energy metabolism in the induction phase of cardioplegia in relation to myocardial temperature during open heart surgery

Changes in myocardial high energy phosphate and lactate concentrations during initiation of cardioplegia for open heart surgery were studied in 21 patients and related to their individual myocardial temperatures. Left ventricular myocardial biopsies were taken 10 min post aortic cross-clamping and were analysed for ATP, creatine phosphate (CP), creatine (C) and lactate. The patients were divided into three groups according to the achieved myocardial temperature: 6-10 degrees C, 11-15 degrees C and 16-24 degrees C. The results indicated that optimal myocardial protection during the induction phase of the cardioplegia was obtained in the 11-15 degrees C group in which the highest ATP concentration and simultaneously lowest lactate concentration was maintained.

Preservation of myocardial high-energy phosphates in open-heart surgery with deep general hypothermia and multidose crystalloid cardioplegia

Myocardial energy metabolism during deep general hypothermia (20 degrees C) and multidose crystalloid cardioplegia, and also during subsequent reperfusion, was studied in eight patients undergoing isolated aortic valve replacement. Six serial transmural biopsy samples from the left ventricular apex were analyzed for high-energy phosphates and their degradation products. Reductions in ATP, total adenine nucleotide content and energy charge were insignificant during cardioplegia, as were changes in adenosine and uric acid concentrations. During reperfusion, however, there was slight but significant reduction in total adenine nucleotide content, despite adequate oxygenation as indicated by reversal of lactate accumulation. These observations suggest that the reperfusion phase is accompanied by metabolic aberrations which are not overcome by good oxygenation in relation to the metabolic rate.

Myocardial metabolism during aortic valve replacement. III. Continuous infusion of cold blood for cardioplegia

Myocardial energy metabolism during hypothermic potassium cardioplegia with blood as the cardioplegia vehicle was studied in eight patients undergoing aortic valve replacement. Cardiac arrest was induced with a single bolus infusion and maintained by continuous perfusion. Myocardial biopsies were taken from the left ventricle 10 min after aortic cross-clamping (a.c.) and immediately before declamping (d.c.) and were analyzed for ATP, creatine phosphate (CP), creatine (C) and lactate. The interindividual range of myocardial temperature was 15-21 degrees a.c. and 17-22 degrees C immediately before d.c. The ATP concentration decreased (12.7 +/- 3.9-10.4 +/- 3.5 mmol X kg-1 dry muscle), the lactate concentration increased (102 +/- 30-156 +/- 8 mmol X kg-1 d.m.), and the total creatine (CP + C) remained constant. Induction of cardioplegia by blood resulting in a mean myocardial temperature of 19 degrees C could not prevent anaerobic metabolism. The changes in ATP levels between 10 min after a.c. and just before d.c. were small, however, indicating that oxygen delivery during continuous blood cardioplegia at a myocardial temperature of c. 20 degrees C prevented further loss of ATP. The lactate concentration, however, increased markedly between 10 min after a.c. and d.c., demonstrating that a significant proportion of the total metabolism was anaerobic.