Importance of Relationship between Ductus and Isthmus in Fetal Diagnosis of Coarctation of Aorta

Background The prenatal diagnosis of coarctation of aorta (CoA) can prove problematic, with relatively high false-positive and false-negative rates. This significantly impacts both prenatal counseling and postnatal management. We sought to evaluate a variety of prenatal echo indices to determine which would best predict neonatal CoA. Methods Fetal echocardiograms of those with prenatal diagnosis of COA were analyzed for the following: diameter of cardiac valves, ascending aorta, distal transverse arch, aortic isthmus, and ductus; right (RV) and left ventricular (LV) length and end-diastolic area and isthmus–ductal angle (IDA). Ratios of RV: LV area, aortic: pulmonary valve diameter, mitral: tricuspid valve ratio (MV:TV ratio), and isthmus: ductal diameter (IDD) were calculated. These measures were compared between those with CoA after birth (CoA group) and those without (no CoA group). Results Of the 62 subjects, 27 were in CoA and 35 in no CoA group. CoA group had a significantly smaller mitral valve, MV:TV ratio, IDD, and IDA compared to no CoA group. The ROC curves for each of these significant measures showed that mitral valve, IDD, and IDA had an AUC of 0.72, 0.80, and 0.83, respectively. Multiple variable model using at least two of these measures had 85% sensitivity and 60% specificity. Conclusions A smaller mitral valve, MV:TV ratio, IDD, and IDA are associated with development of neonatal coarctation. In cases with suspected prenatal diagnosis of CoA, careful evaluation of the relation between the isthmus and the ductus arteriosus using IDD and IDA may enhance the diagnostic accuracy of fetal echocardiograms.