[MB isoenzyme of myocardial creatino-kinase: activity curves in the blood, after ischemic cardiopathy surgery]. / Isoenzima MB da creatino-quinase miocárdica (CK-MB): curvas de actividade no soro, após cirurgia de cardiopatia isquémica.

OBJECTIVE: To determine the curve of cardiac creatine-kinase (MB-CK) plasma activity, in patients with coronary heart disease who were submitted to Coronary Artery Bypass Graft (CABG) and/or aneurysmectomy, in order to evaluate the degree of a eventual myocardial lesion occurring during the first 72 hours after surgery. DESIGN: Assay of the plasma MB-CK activity and of the 12 lead electrocardiogram (EGC) during the first 72 hours after surgery. SETTING: Patients undergoing surgery in a Department of Cardiac Surgery. PATIENTS: 49 consecutive patients included in 2 groups: Group A: 38 pts submitted to CABG. Group B: 11 pts submitted to aneurysmectomy (6 of them with simultaneous CABG). INTERVENTIONS: Determination of plasma MB-CK activity and execution of 12 lead EGC before surgery and at 0, 6, 12, 24, 36 and 72 hours after surgery. RESULTS: Using as a reference the MB-CK values in a control group undergoing surgery for either aortic or mitral valvulopathy, the patients in group A were subdivided: Group A1: 25 pts which curves of MB-CK activity were similar to the control group; none showed sign of myocardial infarction in the EGC. Group A2: 13 pts which curves of MB-CK activity showed a increased value when compared to controls (at least, two Standard Deviation above the medium control value). In 6 of them the EGC were compatible with acute myocardial infarction. Group B patients were also divided in 2 subgroups: Group B1: 10 pts with a similar MB-CK activity to the control group. Group B2: 1 patient with MB-CK activity similar to the patients in Group A2 and whose EKG showed a pattern of "the new" myocardial infraction. CONCLUSIONS: The method used in our work allowed us to define a MB-CK activity curve that translates the expected variability after surgery in patients submitted to CABG and/or aneurysmectomy. This curve allows the distinction between myocardial lesion due to surgical aggression and a ischemic lesion. The EGC although a method with high specificity has apparently a low sensitivity for the detection of myocardial necrosis after CABG. The aneurysmectomy "per se" does not influence the MB-CK activity.