Association of right aortic arch and agenesis of ductus arteriosus in prenatal tetralogy of Fallot spectrum and its clinical implications

ObjectiveIn our center, we observed an increased frequency of right aortic arch (RAA) with an agenesis of the ductus arteriosus (ADA) in prenatally diagnosed tetralogy of Fallot (ToF) and its variations. This study aimed to determine whether there is an association of RAA and ADA in fetuses with ToF. Distribution of genetic anomalies and impact on postnatal outcome were further evaluated.MethodSingle-center retrospective observational study including pregnancies with prenatal diagnosis of ToF from 2010 to 2023. All cases were subdivided into ToF with pulmonary stenosis (PS) and pulmonary atresia (PA). Clinical and echocardiographic databases were reviewed for pregnancy outcome, genetic anomalies, and postnatal course.ResultsThe cohort included 169 cases, 124 (73.4%) with ToF/PS and 45(26.6%) with ToF/PA. Agenesis of the ductus arteriosus was significantly associated with RAA in both subtypes of ToF (p = 0.001) compared to left aortic arch and found in 82.5% (33/40) versus 10.7% (9/84) of fetuses with ToF/PS and in 57.1% (8/14) versus 12.9% (4/31) of fetuses with ToF/PA. In both ToF/PS and ToF/PA, RAA/ADA versus RAA/patent DA revealed a significantly higher risk for the presence of genetic abnormalities, especially microdeletion 22q11.2, major aorto-pulmonary collateral arteries and a shorter time to complete surgical repair.ConclusionWe demonstrated a significantly increased frequency of RAA/ADA in patients with prenatally diagnosed ToF. Although this association revealed no significant impact on overall survival, the prenatal detection of RAA/ADA has implications for counseling, genetic evaluation and postnatal management. What's already known about this topic?Right aortic arch (RAA) has been associated with prenatal diagnosis of tetralogy of Fallot (ToF).What does this study add?In fetuses with ToF, prenatal diagnosis of RAA is significantly associated with an agenesis of the ductus arteriosus (ADA). RAA/ADA is the predominant variant with a higher risk of adverse outcomes and a different distribution of genetic abnormalities. If ADA is suspected, variants of origins of the DA or a major aorto-pulmonary collateral arteries (MAPCA) should be excluded postnatally.