A 1-day-old girl undergoes routine congenital heart disease screening in the newborn nursery. The patient was born via spontaneous vaginal delivery to a 23-year-old primigravid woman after an induction of labor at 40 weeks gestation. The pregnancy and the delivery were uncomplicated, and the patient has stayed with her mother since delivery. The patient is breastfeeding and has voided and stooled twice. Pulse oximetry obtained while breathing room air is 99% oxygen saturation in the right hand and 91% in the right foot. The patient is well appearing. No cyanosis is seen. Femoral and brachial pulses are 2+. Which of the following is most likely cause of this patient's clinical presentation?
Persistent pulmonary hypertension of the newborn | |
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This patient's low postductal (right foot) saturation relative to her preductal (right hand) saturation is consistent with a right-to-left shunt across a patent ductus arteriosus. Because this patient has strong distal pulses, the most likely diagnosis is persistent pulmonary hypertension of the newborn (PPHN).
At birth, physiologically elevated pulmonary vascular resistance (PVR) normally decreases with oxygenation and ventilation of the lungs. In PPHN, also known as persistent fetal circulation, the PVR remains elevated. Deoxygenated (blue) blood crosses from the pulmonary artery into the aorta and mixes with oxygenated (red) blood pumped from the left ventricle, resulting in a relatively lower postductal saturation.
Risk factors for PPHN include conditions associated with lung hypoplasia (eg, congenital diaphragmatic hernia, Potter sequence), infection (eg, pneumonia), or meconium aspiration. However, some patients have no identifiable cause and simply have a slower decline in PVR, resulting in mild right-to-left shunts that can persist into the first few days of life, as is likely in this neonate. Respiratory distress and cyanosis are common, but some infants are asymptomatic.
(Choice A) Right-to-left shunting across the ductus arteriosus also occurs in conditions in which left ventricular output is obstructed such as coarctation of the aorta. However, these infants have diminished femoral pulses and often lower extremity pallor due to decreased distal blood flow. This patient has normal femoral pulses, making hypoplasia of the aortic arch unlikely.
(Choice B) Left-to-right intracardiac shunts (eg, atrial septal defect, ventricular septal defect) cause oxygenated blood to return to the right-sided circulation before being pumped to the lungs again. Unlike in this patient, pre- and postductal saturations would be equal and normal.
(Choices C and E) Total anomalous pulmonary venous return causes oxygenated blood to return to the right side of the heart; affected infants have a right-to-left intracardiac shunt to provide systemic blood flow. Similarly, conditions with right ventricular outflow tract obstruction (eg, tricuspid atresia, tetralogy of Fallot) require right-to-left intracardiac shunting through a septal defect. These infants are often cyanotic and do not have a gradient between pre- and postductal saturations because all mixing is intracardiac, occurring before the ductus arteriosus.
Educational objective:
Persistent pulmonary hypertension of the newborn is characterized by abnormal persistence of elevated pulmonary vascular resistance, causing right-to-left shunting across a patent ductus arteriosus. Patients have a low postductal saturation compared to the preductal saturation and normal distal pulses.