EFFECTS OF AGE AND ISCHEMIC TIMES ON BIOCHEMICAL-EVIDENCE OF MYOCARDIAL INJURY AFTER PEDIATRIC CARDIAC OPERATIONS

Introduction: The vulnerability of pediatric myocardium to ischemia is poorly documented in the clinical setting. Methods: Serial measuremen ts of serum concentrations of myoglobin, the MB isoenzyme of creatine kinase, and cardiac troponins T and I and their respective areas under the curve were obtained, with particular reference to age and ischemi c time, in 80 children undergoing cardiac operations. Sixteen (the con trol group) did not require cardiopulmonary bypass and 64 did. Results : In the control group there were increases (p < 0.01) in myoglobin an d creatine kinase MB isoenzyme but no increase in cardiac troponin T o r I; by contrast, the group treated with cardiopulmonary bypass had si gnificant increases in all four markers but with differing temporal pa tterns. Younger age (especially <12 months) was a highly significant e xplanatory variable only for the release of cardiac troponins T and I, and ischemic time was a significant explanatory variable for the rele ase of creatine kinase MB isoenzyme, cardiac troponins T and I, but no t myoglobin. In comparison with previous studies in adults, creatine k inase MB and cardiac troponin T concentrations were three times greate r in children than in adults. Conclusions: This study supports the spe cificity of cardiac troponins T and I as markers of myocardial injury after pediatric cardiac operations and defines the importance of age a nd ischemic time in determining their release. In comparison with prev ious data in adults, our results raise the possibility that the pediat ric heart may be more vulnerable to the effects of ischemia and reperf usion. Cardiac troponins will permit comparison of new myocardial prot ective strategies or other potentially therapeutic myocardial interven tions.