Measurement of the Great Vessels in the Mediastinum Could Help Distinguish True From False-Positive Coarctation of the Aorta in the Third Trimester

Objective. We investigated the utility of analyzing prenatal mediastinal measures of the great arteries in distinguishing true coarctation of the aorta (CoA) from false-positive CoA. Methods. All fetuses in this study had suspicion of CoA based on the presence of right-left heart disproportion. We defined 3 study groups: group 1, true fetal CoA; group 2, false-positive fetal CoA with a narrow aortic arch; and group 3, false-positive fetal CoA without a narrow aortic arch. Results. In group 1, the mean mediastinal pulmonary artery (PA) to ascending aorta (Ao) diameter ratio ± SD was 2.03 ± 0.48, and in group 2, the ratio was 1.60 ± 0.23. The difference was statistically significant (P = .0018, t test). In group 3, the mean PA:Ao ratio was 1.35 ± 0.14. The difference between groups 1 and 3 was statistically significant (P = .0002, t test). In our study group, for a PA:Ao ratio of 1.60, sensitivity was 83.0%; specificity, 85.0%; positive predictive value, 62.5%; and negative predictive value, 94.0%. Conclusions. In the third trimester, the main PA:Ao ratio as measured in the fetal mediastinum can be a helpful tool in distinguishing true CoA requiring neonatal cardiac surgery from false-positive CoA and simple disproportion requiring medical attention but no surgery in the first month of postnatal life. Key words: coarctation of the aorta; great vessels; mediastinum; third trimester. ntenatal diagnosis of coarctation of the aorta (CoA) is a challenge, although it is critically important for early treatment of the neonate. 1-3 Echocardiography allows for identification of groups at high risk but does not predict with certainty the presence of a CoA after birth. Echocardiographic markers suggestive of CoA in the fetus are many and include a visual disproportion in size between the ventricles, with the right heart larger than the left, visualization of a narrow aortic isthmus or aortic shelf, the presence of a left superior vena cava, and a bicuspid aortic valve. In the third trimester of pregnancy in an otherwise structurally normal heart, substantial right-left heart size disproportion raises the possibility of the diagnosis of CoA with the need for delivery at an appropriately equipped center for performance of a cardiovascular evaluation and postnatal echocardiography. However