Background The aberrant right subclavian artery (ARSA) is the most common branching abnormality of the aortic arch, with an estimated prevalence of 0.5–2% of the population. This anomaly is defined anatomically by the unusual course of the right subclavian artery (RSA), which arises as a fourth vessel from the descending aorta, arriving at the right arm via a path looping behind the trachea and the oesophagus. ARSA is usually asymptomatic in children and poses no implications from the cardiovascular point of view. Pathological and clinical studies have shown the prevalence of ARSA to be significantly increased in individuals with congenital heart defects (CHD) and particularly so, in those with trisomy 21. Several papers have also suggested a strong association of ARSA with other chromosomal and genetic syndromes including 22q11.2.deletion.
Objectives The aim of this study was to describe the prevalence of chromosomal and non-chromosomal syndromes and CHD in a series of 360 consecutive fetuses diagnosed with ARSA in our fetal cardiology clinic.
Material and methods Retrospective analysis of fetuses diagnosed with ARSA during an eight years period (2006–2014). Diagnosis of ARSA was made in transverse three-vessels/arch view with colour flow mapping (Figure 1). Invasive prenatal diagnosis was discussed according to the risk for aneuploidies as adjusted for the presence of ARSA and/or associated cardiac and extra-cardiac abnormalities. Prenatal data were combined with outcome obtained from medical records, pathological examinations and telephone interviews with patients.
Results ARSA was an isolated cardiac finding in 78% (281/360) of cases and associated with a major CHD such as tetralogy of Fallot and hypoplastic left heart syndrome in 22% (79/360). A full karyotype was performed in 60% (217/360) of pregnancies, including 83% of those with ARSA and CHD (66/79) and 54% (151/281) of those where ARSA was an isolated cardiac finding. An abnormal karyotype including trisomy 21 and 22q11.2 deletion was found in 64% (42/66) of cases where ARSA was associated with complex CHD. Trisomy 21 was detected in 25% (37/151) of fetuses with ARSA as an isolated cardiac finding and other aneuploidies in further 7% (11/151) of cases. In our series, there were no cases with 22q11.2 deletion identified where ARSA was an isolated cardiac finding and the majority (76%; 213/281) were livebirths with uneventful postnatal outcome.
Conclusions Our results are consistent with published literature, which suggests that finding of an ARSA should prompt referral to a specialist fetal cardiologist to rule out underlying cardiac defects. A detailed fetal anomaly scan should be performed in order to examine for features of chromosomal abnormalities and invasive testing should be discussed accordingly. If the fetal karyotype is normal and there are no significant cardiac/extracardiac defects, an isolated ARSA is a benign finding with a good postnatal outcome. There is insufficient data from our study to report on association of ARSA with 22q11.2deletion.
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