Coarctation of the aorta is a discrete narrowing of the aortic arch, typically located between the origin of the left subclavian artery and the more distal insertion of the ductus arteriosus. Coarctation accounts for 5% to 8% of patients with congenital heart disease (CHD) and is one of the most commonly missed forms of CHD. The acute physiologic effects of a significant coarctation or other aortic arch obstruction include progressive hypoperfusion of the lower body, with potential development of metabolic acidosis, tachycardia, tachypnea, diminished cardiac function, and, in severe cases, shock. The effects of a coarctation may not be evident early in life because the ductus is usually patent and provides flow to the descending aorta distal to the level of the obstruction. Once the ductus closes, all systemic flow must traverse the aortic arch. If there is a significant coarctation, the negative physiologic effects described above will ensue. In cases of milder coarctation, the patient may not develop acute symptoms, but early detection of coarctation of the aorta is vital in preventing premature cardiovascular disease and long-term systemic hypertension.

The timing of ductal closure can make early diagnosis of coarctation of the aorta difficult because lower body blood flow is adequately maintained as long as the ductus is patent. The patent ductus will typically begin closing in the first few hours to a couple of days of life. It is important that a thorough cardiac examination with emphasis on evaluation of potential coarctation be performed during this time frame, as well as into the first several well child visits. As the ductus closes, an increasing volume of blood will be forced through the narrowed coarctation area to provide lower body flow. This may create a murmur on auscultation, but the murmur can be difficult to differentiate from that of a closing ductus. Because the murmur is nonspecific, evaluation of central pulses and peripheral blood pressure in all four extremities is of the utmost importance in the newborn cardiac examination. When there is a significant coarctation of the aorta in the absence of adequate ductal flow, one can appreciate diminished pulse volume in the central pulses distal to the area of the coarctation. The blood pressure in these extremities will also be lower, and the examiner may appreciate a delay in the timing of the pulse in those extremities distal to the narrowing. It is important that the pulses and blood pressure be assessed in all four extremities, not just the right arm and a leg. The presence of an aberrant right subclavian artery could place the origin of that vessel distal to the level of the coarctation, which would make the blood pressure and pulses in the right arm lower than what would be expected, thus “masking” the coarctation. It is also important that the evaluation be performed in all extremities with the child quiet and at the same approximate time so as to minimize error created by changes in blood pressure secondary to agitation or other physiologic changes. An evaluation for coarctation should be performed in any patient with a blood pressure differ- ence between extremities of >20 mm Hg, systemic hypertension, a palpable difference in pulse strength, or absent femoral pulses.