Cardioplegic arrest in pigs. Effects of glucose-containing solutions

A clinically used cardioplegic solution was evaluated in the laboratory in an attempt to elucidate the value of glucose in maintaining the glycogen and energy stores of the myocardium during aortic cross-clamping. In one group of animals the cardioplegic solution contained glucose; in the other group it did not. Energy stores were determined in full-thickness biopsies of left ventricular myocardium taken prior to bypass, at 60 minutes of cardioplegic arrest, and after 20 minutes of reperfusion. At the end of cardioplegic arrest, glycogen levels were slightly higher than control values, with no differences between the groups. Creatine phosphate (CP) and adenosine triphosphate (ATP) fell by 69% to 73% and 43% to 55%, respectively, from the control values, but there were no statistical differences between these groups. At the end of reperfusion, glycogen and CP stores had returned to control but ATP concentration remained below control values in both groups. These results indicate that glucose is of no value either to maintain myocardial glycogen or to influence the changes in CP and ATP during cardioplegic arrest. The dissociation between the complete and partial restoration of CP and ATP stores to control levels during reperfusion suggests either that ATP consumption is greater than the energy transfer between CP and ADP:ATP systems or that the energy transfer is defective under these experimental conditions.