Beta-enolase in blood plasma during open heart surgery

The enolase isoenzyme composed of the beta subunit (alpha beta or beta beta enolase) is distributed predominantly in the heart and skeletal muscles. To see whether it may be a useful indicator of myocardial damage, concentrations of beta-enolase (the beta subunit of enolase) were determined in serial blood samples taken from 18 patients who underwent mitral valve replacement, using a highly sensitive enzyme immunoassay method. They were compared with those of creatine kinase MB isoenzyme (CK-MB) in the same samples. The mean arterial beta-enolase concentration was 6.60 (SD 3.84) ng.ml-1 at the beginning of anaesthesia. It increased rapidly after reperfusion and rose to greater than 100 ng.ml-1 at 2 h post-reperfusion. It remained high until 12 h post-reperfusion, and then decreased slowly. The plasma beta-enolase concentrations were significantly higher in coronary sinus samples than in arterial samples in the early phase after reperfusion. Since plasma carbonic anhydrase III, which is known to be localised only in the skeletal muscle, did not increase during the surgery, we suggest that the major portion of the elevated plasma beta-enolase was derived from heart muscle. Plasma concentrations of beta-enolase increased as quickly as those of CK-MB after reperfusion. The CK-MB concentrations had returned to normal at 2 d but the beta-enolase concentrations remained elevated up to 7 d. These results show that the determination of beta-enolase in plasma may be useful for estimating myocardial damage during open heart surgery.