Prenatal Diagnosis of Coarctation
In fetuses with qualitative right ventricular (RV) enlargement, which prenatal echocardiographic features predict post-natal coarctation?
From 2007-2013, all fetal echocardiograms and their subsequent post-natal studies from a single center were evaluated retrospectively. Pre- and post-natal right and left heart and aortic arch dimensions were obtained. Each variable for fetuses and infants was tested between patients with and without coarctation. Patients with anomalous pulmonary venous return, Shone’s complex, interrupted aortic arch, Ebstein’s anomaly, or hypoplastic left heart syndrome were excluded.
Out of nearly 3,000 fetuses, 31 were found to have qualitative RV enlargement at 20-34 weeks. Of these, one third (n = 11) were confirmed to have coarctation post-natally. Of the 20 without coarctation, 12 were normal and 4 had ventricular septal defects. Others were found to have premature ductal constriction, agenesis of the ductus venosus, aortic and pulmonary stenosis, sinus venosus atrial septal defect, and primary pulmonary hypertension. Fetal parameters associated with coarctation that tracked into the neonatal period included aortic isthmus z score of <-4.3, an abnormal carotid:subclavian index (CSI; ratio of aortic arch diameter at the left subclavian artery to the distance between the left carotid and left subclavian) of <0.77, and a smaller aortic annulus (mean z score <-1.2). A smaller mitral valve annular size (mean z score <-2.8) was associated with coarctation in utero, but this did not track post-natally.
An abnormal CSI, smaller aortic isthmus, and smaller mitral and aortic valve annuli measured prenatally were associated with the post-natal diagnosis of coarctation of the aorta.
RV predominance may be a normal finding in utero. Distinguishing the normal fetus from the one with coarctation is a challenge, as obtaining reliable views of the fetal aortic arch is operator and patient dependent. Furthermore, the presence of a patent ductus arteriosus may obscure its presence. However, when right heart enlargement is seen, detailed scanning is warranted. With improvement in ultrasound technology and increasing operator experience, subtle abnormalities will be recognized and the imperfect prediction of post-natal coarctation will be refined.
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