1985 Volume 49 Issue 1 Pages 75-80
Isolated rat heart preparations were used to determine the effect of cardioplegia on myocardial metabolism during profound hypothermic (15°C) ischemia. The hearts were grouped according to the components of cardioplegia and the mode of administration. The six groups were normokalemic (GI), calcium-containing hyperkalemic (GII), calcium-free hyperkalemic (GIII) and single does (A), multidose (B). Following 120 min of ischemia, tissue ATP decreased from 25.4±2.2 to 10.3±2.7, 3.9±2.4, 4.1±1.2, 15.5±3.2, 14.5±2.4 and 20.0±2.7 (I-A vs II-A p<0.005, I-A vs III-A p<0.005, I-B vs III-B p<0.05, II-B vs III-B p<0.005), and tissue lactate increased from 9.6±1.5 to 163.4±12.2, 174.1±13.5, 166.8±21.3, 99.1±8.3, 102.6±12.2 and 83.5±9.3 (I-B vs III-B p<0.02, II-B vs III-B p<0.02) μmol/dry wt g, in GI-A, GII-A, GIII-A, GI-B, GII-B and GIII-B, respectively. The results of this study suggests that (1) potassium cardioplegia in a single dose does not prevent degradation of high energy phosphate (HEP) in the hypothermic arrested heart, (2) though multidoes cardioplegia is effective in preserving HEP during ischemia, the extent of its effects varies with the composition, and (3) the omission of calcium is beneficial in GIK cardioplegia in terms of preserving HEP at the end of ischemia.
