Serum Concentration of Myosin Light Chain I and Left Ventricular Shortening Fraction in Neonates

We compared the serum concentrations of myosin light chain I (MLC-I) and left ventricular shortening fraction (LVSF) measured by echocardiography of 13 normal neonates with those of 38 neonates with fetal distress, neonatal asphyxia, or cardiovascular/respiratory diseases not associated with structural abnormalities. The diseased group included 9 neonates with elevated MLC-I concentrations and 18 with low LVSF. Elevated MLC-I concentrations were frequently noted in neonates with transient myocardial ischemia and persistent pulmonary hypertension of the newborn, suggesting a high specificity of MLC-I elevation in these diseases. Although echocardiographically determined LVSF identifies the affected sections of the myocardium, it did not allow rating of the severity of the disorder. There was no correlation between MLC-I and LVSF probably due to therapeutic interventions and pulmonary hypertension. Our results suggest that MLC-I is a useful marker of neonatal myocardial diseases.