The Predictive Value of the CSA Index in the Prenatal Diagnosis of Aortic Coarctation in Ultrasound Examination Performed during the Second Trimester

Background: Aortic coarctation (CoA) is the fourth most common congenital heart defect (8–10%) which occurs at a frequency of about 20–60/100,000 births. Only 22.3% of all cases appears to be diagnosed during the second trimester of pregnancy. Since the detection of prenatal aortic coarctations is very low, every effort should be made to change this situation. According to the authors of this study, the CSAi (carotid to subclavian artery index) could serve as a reliable indicator. Material and Methods: Ninety-six fetuses from healthy, single, pregnancies, with good ultrasound visualization between 18 and 27.5 weeks of gestation, and twenty-three fetuses suspected of aortic coarctation (postnatally confirmed) were included in this study. Our first aim was to compare the current most common method of prenatal CoA diagnosis based on the measurement of the aortic z-score in the aortic isthmus using the method suggested by us-CSAi. Results: Logistic regression coefficients for z-score and CSAi were analyzed as predictors of coarctation occurrence. It appears that 39.4% of coarctation occurrence can be predicted on the basis of the z-score, and 93.5% on the basis of the CSAi. The cut-off value for CSAi in the study group was 0.81 (sensitivity: 95.7%, specificity 99%). Based on the ROC curve analysis, the cut-off value for the carotid to subclavian distance (mm) was determined; the risk of coarctation increased above this value. Based on the Gini index (0.867), this value was set at 2.55 (sensitivity 82.6%, specificity 93.7%). Conclusions: CSAi measurement is currently the most sensitive method for aortic coarctation detection. For the purpose of our study, this method was applied in diagnostics in the second trimester of pregnancy. This method is easy, reproducible and should be widely introduced into everyday echocardiographic diagnostics of coarctation to minimize the risk of error.