DIAGNOSTIC EVALUATION OF CREATINE KINASE ISOENZYMES IN CHILDREN

Abstract

In adults, plasma elevations of creatine kinase isoenzymes are highly specific for myocardial necrosis, however, the diagnostic sensitivity and specificity of MB CK in children have not been determined. Accordingly, we analyzed the CK isoenzymes by a kinetic fluorometric method in serial plasma samples from 89 patients, aged 1 day - 17 yrs, mean 3.9 yrs, and 34 controls, 1 mo - 18 yrs, 6.1 yrs. 57 pts. had cardiac catheterization (cath) and angiography. Cyanotic group included tetrology (2), transposition (3), atrioventricular canal (3), truncus (1), total anomalous pulmonary venous return (2), and combinations (9); acyanotic group included septal defects (13), valvular lesions (10), patent ductus arteriosus (6), idiopathic hypertrophic subaortic stenosis (2), endocardial fibroelastosis (1), pericarditis (1), and combinations (4). 31 pts. had cardiac surgery for congenital defects. Blood samples were collected prior to cath or surgery and q6H × 2 thereafter. CK isoenzymes were assayed with and without creatine phosphate, the specific CK substrate, and results compared to controls. MB CK was normal in control, pre cath and pre surgery samples (<.005 IU/ml). After cath, despite total CK elevations in 91%, with up to 12-fold increase, MB remained normal in 88%. However, after cardiac surgery, total and MB CK were elevated in all pts. Thus, elevated plasma MBCK in the pediatric population appears to be a sensitive and specific indicator of acute myocardial damage.