Myocardial metabolism during aortic valve replacement: II. Bolus Infusion of Cold Blood for Cardioplegia

Abstract

Myocardial energy metabolism during hypothermic potassium cardioplegia with blood as the cardioplegia vehicle, given in one or two bolus doses, was studied in eight patients undergoing aortic valve replacement. 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 11–19°C at 10 min a. c. and 11–25°C immediately before d.c. The myocardial ATP concentration fell (17.2±5.7–12.8±2.8 mmol × kg^-1 dry muscle), the lactate concentration rose (64.7±35.8–136±33.8 mmol × kg^-1 d.m.) and the total creatine pool (CP + C) was unchanged. Hypothermic blood cardioplegia conferred fairly good initial protection of the myocardium, but the reduction in ATP and the great lactate accumulation towards the end of cardioplegia, especially in patients with myocardial temperature reaching 19–25°C, indicates that such protection is adequate only if the myocardial temperature is maintained between 11 and 18°C.