P3D256: To Steal or Not to Steal: A Rare Pediatric Case of Congenital Isolated Left Subclavian Artery

Introduction: Subclavian steal syndrome refers to the reversal of blood flow from the vertebral artery (VA) to the ipsilateral subclavian artery (SA), leading to transient ischemia of the brain or arm. It is commonly seen as an acquired defect in adults from atherosclerotic obstruction as well as secondary to surgical correction for congenital heart defects or coronary artery bypass. Rarely, it arises from isolation, agenesis, or anomalous artery formation. In extremely rare cases an SA can arise from a VA.

Case Description: An 8-year-old female with 22q.11 deletion and right aortic arch was found to have an isolated connection from the VA to the left SA. At 17 days of life, her first echocardiogram, performed due to a murmur on exam, revealed pulmonary artery branch stenosis and a right aortic arch. Though this imaging modality was limited, an anomalous right SA and common origin of the left subclavian and carotid arteries were suspected. At the time, the anatomy was not further investigated by other more sensitive imaging modalities given the risks of sedation and radiation in an asymptomatic patient. Periodic echocardiograms continued until 7 years of age, when she developed coughing after crying, eating, and during exercise. The risk for a potential vascular ring prompted a computed tomography angiography (CTA) study. No vascular ring was seen; however, the left SA origin was unclear and suspected to arise from the left VA. To further characterize this anatomy, a carotid ultrasound was completed, showing retrograde flow within the left VA. With the CTA, this suggested an isolated origin of the left SA from left VA.

Discussion: We report a patient with a rare congenital finding of a right aortic arch with an isolated left SA supplied by the left VA. This is only the sixth reported case of isolated left subclavian artery without a patent ductus arteriosus in the pediatric population. This patient was known from infancy to have a cardiac anomaly; however, due to limitations of echocardiography, the specific origin of the left SA was not found until a CTA and carotid ultrasound were performed. Though this congenital anomaly did not explain the patient’s symptoms (later suspected to be due to gastroesophageal reflux), we now know the child has the potential of presenting with symptoms of subclavian steal syndrome in the future. Combining CTA and ultrasound, we were able to define the anatomy and physiology of her anomaly without the need for additional sedation or radiation.

Conclusion: Our case highlights the importance of choosing specific imaging modalities in pediatric patients with congenital aortic arch anomalies, consideration of the risk-benefit ratio of performing certain studies and the potential for subclavian steal syndrome.