Cardiac function of neonates with congenital hypothyroidism before treatment.

Because of previous reports of myocardial dysfunction in adults and children with hypothyroidism, 12 newborns with congenital hypothyroidism were studied using standard electrocardiographic and echocardiographic techniques. The infants were between the ages of 7 and 28 days at the time of study. Five infants were athyrotic, and of these two had delayed skeletal maturation. Electrocardiogram revealed normal heart rates and QRS voltages in all children, while five had abnormal dome-shaped T-waves and absent ST-segments (Mosque sign). Echocardiograms were normal in all patients indicating no myocardial dysfunction or pericardial effusion. This study suggests that myocardial dysfunction is not present in the immediate newborn period of infants with congenital hypothyroidism. It is reasonable to conclude that early detection of congenital hypothyroidism by mass screening may prevent the cardiac affects of hypothyroidism as well as the other known sequelae.