Impact of prospective measurement of outflow tracts in the prediction of coarctation of the aorta

Background: Prenatal diagnosis of coarctation of the aorta (COA) is associated with reduced mortality and morbidity, however, accurate prenatal prediction remains challenging. To date, studies have measured the outflow tracts retrospectively to gauge the potential to predict COA. Our primary objective was to evaluate prospectively acquired measurements of the outflow tracts in prenatally suspected COA. A secondary aim was to report the postnatal prevalence of bicuspid aortic valve in this cohort.

Methods: Measurement of the aortic valve, pulmonary valve, distal transverse aortic arch (DTAA) and arterial duct (AD) diameters were undertaken routinely in fetuses with suspected COA between 2002–2017. Using published reference ranges based on >7000 fetuses from our own unit, z scores were computed.

Results: COA was confirmed after birth in 77/149 (52%) cases. DTAA z score and the z score of DTAA:AD were smaller in cases with confirmed COA compared to false positive (FP) (-2.8 vs -1.9, p=0.039; -3.13 vs -2.61, p=0.005, respectively). Multiple regression analysis demonstrated that z scores of DTAA and AD were the only significant predictors (p=0.001). Bicuspid aortic valve was identified in 30% of the FP group.

Conclusion: Measurement of the DTAA and AD z scores can be used to attribute risk for postnatal COA in a selected cohort. The significance of the high incidence of bicuspid aortic valve in FP cases merits further study both with respect to aetiology and longer- term significance.