14 Coarctation of the Aorta
A 28-year-old white woman, gravida 2, para 1+0, was referred at 22 weeks’ gestation by the obstetrician for ventricular disproportion (right ventricle [RV] larger than left ventricle [LV] for gestation).
6. Flow in both the aortic and ductal arches is normal and antegrade. The aortic arch, however, is hypoplastic distally between the left common carotid artery and the descending aorta. There appears to be a posterior shelf consistent with coarctation of the aorta (CoA) (Fig. 14-1).
a. Following delivery of a baby with a prenatal diagnosis of probable CoA, prostaglandin E1 (PGE1) may be initiated if the coarctation is clearly more severe, with significant arch hypoplasia, or if there is a concern that the left heart size may be borderline, particularly if there is retrograde distal arch flow.
c. Lack of blood pressure differences while the ductus arteriosus is still patent is the norm because the ductus arteriosus may be providing critical blood flow to the lower body beyond the level of the coarctation.
e. In critical neonatal CoA, the ductus arteriosus often supplies blood flow to the distal arch. The hyperoxia test would in such a state reveal a normal Pao2 (>250 mm Hg) in the preductal area, whereas the postductal area will fail the hyperoxia test as a result of right-to-left shunting through the ductus arteriosus. Occasionally, where there is a discrete coarctation, the baby passes preductal and postductal hyperoxia tests.
f. The two-dimensional echocardiogram shows the site and extent of coarctation. The Doppler examination reveals a disturbed flow distal to the coarctation and signs of delayed emptying in the proximal descending aorta, with continuous flow through the distal arch beginning at the most proximal point of significant arch hypoplasia or obstruction. In the presence of a patent ductus, there is usually no gradient across the coarctation.
g. In borderline situations, or when the infant passes the hyperoxia test and there is still suspicion of coarctation, the ductus could be allowed to close while the vital signs and blood pressures are monitored in the intensive care unit, with follow-up echocardiography to confirm the diagnosis. Ductal constriction can result in a discrete shelf’s evolving at the site of the distal arch where the ductus joins the aorta. This type of coarctation can continue to evolve even weeks to months beyond the neonatal period.
d. Balloon angioplasty or stenting is the treatment of choice for recurrent coarctation, and in some institutions it is used more routinely for discrete native coarctation identified in older infants and children.
4. Yearly surveillance by clinical examination, echocardiography, and cardiac magnetic resonance imaging (MRI) is necessary. This surveillance monitors persistent systemic hypertension due to residual narrowing proximal to the arch repair and development of an aneurysm of the aorta near the site of repair.
5. Reassessment for subvalvar and valvar aortic stenosis or mitral stenosis should be performed at follow-up, given the common association and their progressive nature, particularly in the first few years of life.
2. The baby passed the preductal hyperoxia test with a Pao2 of 275 mm Hg, but the postductal Pao2 was 80 mm Hg, suggesting significant right-to-left shunting through the ductus arteriosus and a critical coarctation.