In the study they demonstrated that total CPK enzyme levels were elevated in all three groups but CPK-MB isoenzymes were elevated only in the myocardial infarction and the bowel infarction groups. There was no difference in either percent CPK-MB or in total international units of CPK-MB between these two groups of patients. Fortunately, the two groups could be distinguished by examining LDH isoenzymes. The LDH-l/LDH-2 ratio was reversed in the myocardial infarction group and remained normal in the bowel infarction group, allowing a sensitive method for differentiation. Lactate dehydrogenase did not rise significantly in the control vascular surgery group. In addition CPK-BB fractions were mildly elevated in the bowel infarction group of patients but in neither of the other groups.
This report is of clinical importance because mesenteric ischemia and bowel infarction are relatively uncommon and are frequently misdiagnosed as a myocardial infarction. The LDH isoenzymes are more specific for documenting myocardial infarction than elevations of CPK-MB isoenzymes that can occur in patients following median sternotomy, esophageal procedures, and bowel infarction.
Evaluation of both CPK and LDH isoenzyme levels drawn within the first 48 hours of an acute episode of suspected myocardial infarction combines the high degree of sensitivity of CPK-MB determination with the high degree of specificity offered by evaluation of LDH isoenzymes. They should not be evaluated alone. Nowhere is the increased discrimination offered by evaluation of both isoenzymes more important than in evaluating a postoperative surgical patient for a possible myocardial infarction. Following open heart surgery, CPK-MB isoenzyme may be elevated from the median sternostomy incision or from trauma to the atria due to cannulation. In the patient who has undergone general surgery, CPK-MB isoenzymes may be elevated if there is vascular compromise or major trauma to the esophagus or intestines. In each case, concomitant evaluation of LDH isoenzymes allows appropriate discrimination from myocardial infarction. This current article by Graeber et al completes a cycle of excellent work that started in the animal laboratory and is herein followed to its clinical conclusion.