A 5-day-old neonate is brought to the hospital due to poor feeding, sweating, pallor, and respiratory distress. The symptoms are exacerbated with feedings. There has been no loss of consciousness or cyanosis during these episodes. She has no fever or cough. The girl was born at 38 weeks gestation via an uncomplicated vaginal delivery. On examination, temperature is 36.7 C (98 F), pulse is 165/min, and respirations are 75/min. Oxygen saturation on room air is 97% in the right hand and 95% in the left foot. She has nasal flaring and retractions. Bilateral fine crackles are present. A gallop is heard over the precordium; there is no murmur. The liver edge is palpable 3 cm below the right costal margin. Extremities are pale and cold. Brachial pulses are strong and femoral pulses are weak. What is the most likely cause of her symptoms?
Coarctation of the aorta | |
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*After closure of ductus arteriosus. BP = blood pressure. | |
This 5-day-old infant has poor perfusion (eg, cold, pale extremities) and manifestations of congestive heart failure (eg, poor feeding, crackles, gallop, hepatomegaly) that developed around the time of expected closure of the ductus arteriosus (first few days of life). The differential pulses and mild oxygen saturation gap between the upper and lower extremities suggests aortic coarctation, a ductal dependent congenital heart lesion.
Aortic arch narrowing (due to a thickened tunica media) leads to decreased blood flow to the descending aorta. With mild narrowing, patients may present with asymptomatic hypertension or lower extremity claudication in childhood or as adults. However, neonates with severe narrowing depend on the ductus arteriosus, which connects the pulmonary artery to the descending aorta (usually distal to the coarctation site), to provide systemic blood flow at birth via right-to-left shunting (from the pulmonary artery to the descending aorta). Upon closure of the ductus arteriosus, distal blood flow drastically diminishes.
This results in poor distal perfusion (eg, cold, pale extremities) primarily affecting the lower extremities (eg, weak femoral pulses) rather than the upper extremities (ie, arm/leg differential pulses and oxygen saturation). The aortic obstruction also increases left ventricular afterload. This creates pressure overload on the left ventricle, leading to heart failure and cardiogenic shock. Classic symptoms include sweating, pallor, and respiratory distress, particularly during periods of exertion (eg, feeding in neonates), due to pulmonary edema and inability to maintain cardiac output. Bilateral crackles and a gallop are often present. Right heart failure can secondarily occur, causing hepatomegaly and peripheral edema.
(Choice A) Poor distal perfusion causes compensatory peripheral vasoconstriction in an attempt to increase blood pressure. Therefore, systemic vascular resistance is increased, not decreased.
(Choices C, D, and E) Due to increased pressure on the left side of the heart as compared to the right, atrial septal defect (ASD) and ventricular septal defect (VSD) cause left-to-right shunting and increased pulmonary blood flow. ASDs are usually asymptomatic in the neonatal period but can cause right heart failure due to volume overload; crackles and a gallop on examination would not be expected. VSDs, although classically associated with a holosystolic murmur, can present with signs of heart failure and lack of murmur when large. However, upper and lower extremity pulses would be similar.
Educational objective:
Severe aortic coarctation, which increases left ventricular afterload, can present in the neonatal period with congestive heart failure (eg, respiratory distress, poor feeding) and cardiogenic shock upon closure of the ductus arteriosus.