A variety of cardiac defects, encompassing truncus arteriosus, tetralogy of Fallot, pulmonary atresia with ventricular septal defect and interrupted aortic arch, are generally summarised as conotruncal malformations. Patients with these cardiac defects were frequently found to have a common microdeletion on chromosome 22, the so-called monosomy 22q11.2. The aim of our study was to determine whether the laterality of the aortic arch or the presence of subclavian artery anomalies (SAA) represent markers for monosomy 22q11.2 in these patients. 170 patients with these cardiac anomalies were recruited at presentation in the paediatric cardiology units of two tertiary referral centres from 1994 until 2003. Of the 170 children and young adults, 33 had interrupted aortic arch, 35 tetralogy of Fallot, 31 truncus arteriosus communis and 71 pulmonary atresia with ventricular septal defect. All were screened for monosomy 22q11.2 and the results were correlated with the laterality of the aortic arch and the presence of SAA contralateral to the aortic arch (aberrant origin from the descending aorta, isolation, distal ductal origin from the pulmonary artery and cervical origin of the right subclavian artery). Monosomy 22q11.2 was present in 59/170 patients (35%). A left aortic arch (LAA) was found in 118 (69%), a right aortic arch (RAA) in 52 (31%) patients. Almost 50% of the patients with RAA (46%), but only 30% of the patients with LAA had monosomy 22q11.2 ( P=0.054). A total of 47 patients (28%) had an anomaly of the subclavian artery, 81% of whom had monosomy 22q11.2. This deletion was found in decreasing percentage in patients with LAA+SAA (85%) >RAA+SAA (75%) >RAA without SAA (28%) >LAA without SAA (13%).
Conclusion: In patients with conotruncal malformations, anomalies of the subclavian arteries are the most important anatomical marker for the presence of monosomy 22q11.2, independent of the laterality of the aortic arch. Therefore, we recommend cytogenetic testing for this microdeletion in all patients with subclavian artery anomalies and conotruncal malformations.