Prenatal Diagnosis of Aberrant Right Subclavian Artery in Unselected North Indian Population: Significance and Counselling

Abstract

This study was carried out to assess the incidence and association of aberrant right subclavian artery in North Indian population and to analyse its significance as a marker of Down syndrome and to formulate an adaptable protocol for counselling and management of such pregnancies. A prospective assessment of 1024 consecutive unselected pregnancies with gestational age between 12 and 34 weeks was carried out from May 2016 to August 2017 at the author's fetal medicine centre in North India. The screening for ARSA was performed with Color Doppler using low PRF at 3 vessel trachea view in axial section followed by confirming of arterial flow pattern by pulse Doppler. Incidence of ARSA in this study was 0.58%. Thirty-three percent of cases of ARSA were associated with other anomalies whereas 66% were isolated. Trisomy 21 was found in 16.6% of cases. ARSA as a marker of Trisomy 21 has a high specificity (99%) but low sensitivity (33%, [95% CI]). Although global likelihood ratio (LR) for ARSA as a marker for Down syndrome was high, the LR for isolated ARSA was nil. Isolated ARSA can be considered a normal variant and does not warrant invasive prenatal diagnosis in the scenario of low biochemical risk. On the other hand, ARSA associated with other markers/ anomalies warrants invasive prenatal diagnosis.

Aberrant Right Subclavian Artery—To Test or Not to Test, That Is the Question

“…Previous studies conducted by Shah, Ranzini et al, and Martínez-Payo et al 1,3,16 that also had nonsignificant results did not find any single cases of isolated ARSA with Down syndrome. However, in our study we had two truly isolated cases associated with Down syndrome and one with Turner syndrome, still the result came not significant (p-value ¼ 0.998).…”

“…Ten patients opted for the termination of pregnancy as a result of trisomy 21 (6), Turner syndrome (1), complete corpus callosum (CC) agenesis with bilateral club foot (1), partial agenesis of CC with hypoplastic NB (1), and absent NB with increased nuchal fold thickness (1). Intrauterine fetal demise occurred in one fetus having ARSA along with coarctation of aorta and left superior vena cava and one fetus with ARSA and atrioventricular septal defect expired at 18 months of age.…”

“…It arises directly from the aorta, as its fourth branch distal to the left subclavian artery and courses behind the trachea toward the right shoulder. [1][2][3] The aortic arch normally gives rise to three branches, the right brachiocephalic trunk, the left common carotid, and left subclavian artery. The right subclavian artery (RSA) and right common carotid arises from right brachiocephalic trunk (►Fig.…”

“…The right subclavian artery (RSA) and right common carotid arises from right brachiocephalic trunk (►Fig. 1) Three vessel trachea view with low pulse repeatation frequency (PRF) settings has made the diagnosis of ARSA relatively easy with the vessel seen originating at the junction of aortic and ductal arch traversing behind the trachea. 3 Confirmation of the diagnosis can be achieved by additional coronal views allowing direct visualization of ARSA coming from aorta toward the right shoulder (►Fig.…”

“…[5][6][7][8][9] However, a few recent studies have challenged this association, thereby creating a dilemma toward the utility of ARSA in diagnosing trisomy 21. 1,3 This study addresses these disputes by retrospectively evaluating the structural and chromosomal abnormalities associated with fetal ARSA along with its clinical outcome.…”