Teaching Case

A 60 year old female presented with left sided chest pain since 2 days. The pain was sudden in onset, dull-aching and radiating to the back. No history of dyspnoea, cough, fever, dysphagia or odynophagia. The past history was non-contributory.

Chest radiographs, frontal and lateral views were performed as primary investigation. Abnormal findings on radiograph prompted a barium swallow study. For further evaluation, magnetic resonance imaging (MRI) of the thorax was carried out.

Radiograph chest, frontal view depicted widening of the superior mediastinum with prominence and calcification at the aortic knob. Mild cardiomegaly was noted. Visualized lung fields appeared normal. Lateral radiograph revealed anterior displacement of the trachea with retrotracheal soft tissue density.

Barium swallow demonstrated extrinsic impressions along the anterior and posterior walls of the upper thoracic oesophagus. No mucosal irregularity or filling defect was noted.

Sequential coronal MR images revealed bifurcation of the ascending aorta into two separate aortic arches on either side of the trachea. The anomalous right arch merged with the left arch posteriorly to form the descending thoracic aorta. Axial MR and maximum intensity projection images depicted two patent aortic arches completely encircling the trachea and oesophagus, forming a complete vascular ring.

Congenital anomaly of the aortic arch is a rare and usually an incidental finding. Vascular rings constitute less than 1% of the congenital cardiovascular diseases and were first identified by Gross in 1945 [1]. Double aortic arch is the most frequent form of arch anomaly that requires surgery for tracheal or oesophageal compression [2]. Respiratory symptoms at birth or during infancy should raise the possibility of a vascular ring. The classic history in a patient with double aortic arch is noisy breathing in the first few weeks of life. Rarely, neonates may present with Acute life-threatening event (ALTE) characterized by episodes of acute apnea and cyanosis.
When both arches are patent, a complete vascular ring is formed. In 73% of cases, the right arch is larger, at a higher level and is located more posteriorly than the left arch [3]. Each arch gives rise to the ipsilateral carotid and subclavian arteries, which ascend symmetrically giving “four vessel sign”. Determination of the dominant arch and anteroposterior relationships of the right and left arches is important to the surgeon, as contralateral thoracotomy is generally indicated [4].
Although there are no pathognomonic features of a double aortic arch on plain chest radiograph, it often reveals significant compression and anterior bowing of the thoracic trachea [5]. Barium swallow is a valuable investigative tool for better appreciation of vascular impressions. Distension of the esophagus by the barium column is important on the frontal view, which depicts right and left esophageal indentations in an S-shaped configuration. The posterior vascular impression of the crossing arch is more apparent on the lateral view [6]. On echocardiography, both patent arches can be readily identified using suprasternal view.
CT angiography with multiplanar reformats (MPR) and volume reconstructions depicts the arterial branching pattern, location and extent of airway and esophageal obstruction and also delineates cardiac anatomy. MRI is equally successful in defining the anatomy and airway compromise. MRI and CT can also depict an atretic segment, if any. Multidetector CT with 3D reconstruction is the single best imaging technique for the diagnosis and characterization of vascular rings [7].
The surgical management of double aortic arch is division of the ring to relieve compression of the trachea and esophagus. In general, this is achieved by dividing the minor arch through an ipsilateral thoracotomy.