Background Isolated right aortic arch (RAA) is felt to be a rare finding, present in around 0.1%. The 3 vessel and tracheal view has been part of the fetal medicine departmental screening since 1998 and has now been incorporated into the national screening guidelines. The objective is to define the prenatal associations and postnatal outcomes of fetuses diagnosed with a RAA in utero.
Methods Retrospective analysis of fetuses diagnosed with an isolated RAA diagnosed at the Harris Birthright Centre for Fetal Medicine between 2000 and 2014. Prenatal and postnatal findings were ascertained from clinical records. Diagnosis of RAA was made in the transverse three-vessel/tracheal view where the aortic arch was demonstrated passing in front of the trachea.(Figure 1) Prenatal data were combined with outcomes obtained from medical records and telephone interviews with patients.
Results 100 cases of isolated right aortic arch were identified in fetal life at a median gestation of 21weeks (range:11–36). The nuchal translucency (NT) was elevated in 10/64 (16%) where the measurement was known and an extracardiac abnormality detected in 23/100 cases of whom 2 had a raised NT. Genetic abnormalities were confirmed in 13/58 (21%) tested cases comprising: 22q11.2 microdeletion (n = 5), trisomy 21 (n = 2), combined 22q11 microdeletion with mosaicism of 45XO (n = 1), unbalanced translocation (n = 1), balanced translocation (n = 1), duplication of chromosome 16p13 with a recessive disorder of lymphogenesis (n = 1) and other syndromes (n = 3). Of those with abnormal genetics 4/13 had no other abnormal fetal sonographic markers.
An aberrant left subclavian artery (ALSCA) was identified in 39/98 (40%), the arterial duct was left sided in 67/75 (89%). In the postnatal period, 3 cases were diagnosed with a double aortic arch. Spontaneous intrauterine death occurred in 6 cases and termination of pregnancy in 9 cases. There were 80 live births and one neonatal death. Five children presented with symptoms of airway obstruction at a median age of 2.9 years (range 1–8). Pulsatile airway compression was identified in all and surgical division of the vascular ring was performed at median age: 2.9years (range: 1–8). Within the past two years, three asymptomatic infants (with RAA, ALSCA, left arterial duct) have been shown by bronchoscopy and cross-sectional imaging to have significant airways compression. Thus, we are currently considering whether all infants with RAA, ALSCA and left duct merit investigation irrespective of symptoms.
Significant genetic abnormalities were identified of which some had no other abnormal fetal sonographic findings.
Many patients were discharged after their first postnatal review, but despite this 8 children have required surgical relief of a vascular ring as a result of pulsatile compression of the trachea.
Lack of symptoms does not exclude significant airways compression and the true incidence of airway compromise may be underestimated.
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