Neonatal hyperthyroidism and heart failure. A differential approach

Congestive heart failure in neonatal thyrotoxicosis is attributed to sympathetic overstimulation of the myocardium with resulting high-output cardiac failure. An additional case of neonatal thyrotoxicosis with congestive heart failure is discussed; three possible causes (thyrotoxicosis, maternal propranolol therapy, and ventricular septal defect) were present. Along with the usual procedures, the echocardiogram is of value in separating these factors. In addition, we discuss the potential dangers to the newborn of a mother receiving long-term propranolol hydrochloride therapy during pregnancy.