Magnetic Resonance Imaging of a Distorted Left Subclavian Artery Course: An Important Clue to an Unusual Type of Double Aortic Arch K.W. Holmes, 1 D.A. Bluemke, 2 L.A. Vricella, 3 W.J. Ravekes, 1 K.M. Kling, 4 P.J. Spevak 1 1 Division of Pediatric Cardiology, Johns Hopkins Hospital, 600 N. Wolfe Street, Brady 501, Baltimore, MD 21287, USA 2 Department of Radiology, Johns Hopkins Hospital, 600 N. Wolfe Street, Baltimore, MD 21287, USA 3 Division of Cardiothoracic Surgery, Johns Hopkins Hospital, 600 N. Wolfe Street, Baltimore, MD 21287, USA 4 Division of Padiatric Surgery, Johns Hopkins Hospital, 600 N. Wolfe Street, Baltimore, MD 21287, USA Abstract. The objective of this study was to deter- mine if distortion of the left subclavian artery course distinguishes double aortic arch with atretic left dorsal aorta from right aortic arch with mirror image branching. We performed a retrospective case series at a tertiary care center. Twenty-six patients under- going magnetic resonance imaging for suspicion of a vascular ring were identified, 6 of whom had an at- retic left dorsal aorta confirmed by surgical inspec- tion. Six patients with the diagnosis of right aortic arch with mirror image branching were identified for comparison. The course of the left subclavian artery was assessed using surface-rendered magnetic reso- nance angiography (MRA) and axial fast spin echo images. All patients with double aortic arch had clinical symptoms suggestive of esophageal or tra- cheal compression. Six patients had double aortic arch, 3 of whom had an atretic left dorsal aorta. In these 3 patients, the branching patterns on MRA mimicked right aortic arch mirror image branching except for the distortion of the initial course of the left subclavian artery. Surgical observation confirmed the presence of an atretic left dorsal aorta that re- sulted in tension on the left subclavian artery pulling it posteriorly and inferiorly and completing the vas- cular ring. Patients with right aortic arch mirror im- age branching demonstrated no such subclavian artery distortion, and these patients did not have clinical symptoms suggestive of a vascular ring. Our results demonstrate that left subclavian artery dis- tortion due to traction by an atretic left arch is an important diagnostic finding in the evaluation 6 pa- tients with suspected vascular rings. Key words: MRI — Vascular ring — Congenital heart disease — Aortic arch A vascular ring is considered when a young child has symptoms of stridor or dysphagia. The diagnosis of a vascular ring can be made on the basis of character- istic findings on barium swallow or identification of vascular anatomy via echocardiography [7]. Al- though angiography has been used to further delin- eate the arch anatomy, recently gadolinium-enhanced magnetic resonance angiography (MRA), or com- puterized axial tomography (CT), has avoided the need for invasive testing [8]. The most common vascular rings include double aortic arch and right aortic arch with an aberrant left subclavian artery [2, 5, 6]. When the dorsal aortic portion of a double arch is atretic, visualization is problematic for imaging modalities depending on the presence of flow (e.g., color Doppler or MRA). In such patients, the atretic left dorsal aortic segment is usually not visualized and the anatomy mimics right aortic arch with mirror image branching (Fig. 1). A right aortic arch with mirror image branching is usually not a true vascular ring and is a finding often associated with additional intracardiac lesions; therefore, the distinction of a right aortic arch from an double aortic arch with atretic left dorsal aorta is clinically important in the symptomatic patient. We hypothesize that an accurate diagnosis is made by noting left subclavian artery distortion, which is the result of traction by the atretic left dorsal aorta. Materials and Methods Patients Patients identified from the Johns Hopkins Hospital Pediatric Echocardiography Laboratory database were reviewed in this ret- rospective case series. We selected patients with the diagnosis of vascular ring from September 1995 to January 2004. Thirty patients Correspondence to: K.W. Holmes, email: kwholmes@jhmi.edu Pediatr Cardiol 27:316–320, 2006 DOI: 10.1007/s00246-005-1118-x