Index of Suspicion in the Nursery

A 1-day-old male infant develops lower extremity cyanosis after feeding. The infant was born at 38 weeks’ gestation and had Apgar scores of 8 and 9 at 1 and 5 minutes, respectively. There were no prenatal complications. Today he has lower extremity saturations of 80% and upper extremity saturations of 97%. Results of limited/preliminary echocardiography are reported as “pulmonary hypertension and possible aortic arch obstruction.” After starting an infusion of prostaglandin E1, the infant is transferred to a tertiary care center for cardiac evaluation. The initial physical examination reveals a warm, pink neonate who is experiencing no significant distress. His length is at the 75th percentile and weight is at the 25th percentile for age. His temperature is 37.0°C, heart rate is 120 beats/min, respiratory rate is 28 breaths/min, and cuff blood pressure in the right upper extremity is 75/45 mm Hg. No blood pressure gradient is evident between the upper and lower extremities. Oxygen saturation in room air is 98% in the left upper extremity and 85% in the left lower extremity. Lungs are clear and no retractions are noted. Cardiovascular examination reveals a fixed, widely split second heart sound (S2) without an appreciable murmur. Pulses are +2 and equal in …