Myocardial Ischaemia in Aphyxia Neonatorum

Serial electrocardiograms and creatine kinase (CK) isoenzyme activities were studied prospectively in 20 asphyxiated term newborn infants and 43 normal neonates. By adapting a previously described grading system for ischaemic changes, a degree of electrocardiographic ischaemia was defined which occurred almost solely in asphyxiated infants. Infants with this degree of abnormality had significantly higher mean CK-MB and MM activities than other asphyxiated infants at 0, 8 and 28 hours. Histological changes of peripartum myocardial necrosis were seen in 4 of the 5 infants on whom an autopsy was performed, and either electrocardiogram or CK-MB was abnormal in all four. It is concluded that myocardial injury in the newborn period is often associated with CK-MB release, but in view of the lack of cardiac-specificity of CK-MB in newborn infants, caution is urged in the interpretation of elevated isoenzyme activity in the neonate.