CARDIOVASCULAR IMAGING: Thoracic Arteries

Case Author: Diana Litmanovich, MD, Beth Israel Deaconess Medical Center

History

1-month-old female with mild wheezing and costal retraction with dusky appearance during crying

Imaging Findings

High-voltage radiograph of the mediastinum (A) shows diffuse narrowing of the trachea and a wide-angle carina. Axial contrast-enhanced CT images of the chest (B-E) show a vascular structure posterior and to the right of the carina, traversing the mediastinum toward the left hilum. It originates from the right pulmonary artery (E) and compresses the trachea, which assumes a rounded, pinpoint shape (CT image, F).

Diagnosis

Pulmonary sling

Teaching Points

Pulmonary sling is a rare congenital vascular anomaly caused by involution of the proximal sixth arch, resulting in an anomalous left pulmonary artery originating from the posterior aspect of the right pulmonary artery. Its course is posterior to the right main bronchus, traversing the esophagus and trachea toward the left lung. Compression of the right main bronchus or trachea between the main pulmonary artery and the pulmonary sling results in tracheal stenosis.

Pulmonary sling is usually associated with congenital airway anomalies, such as congenital tracheal stenosis and tracheomalacia, contributing to respiratory distress. In type 1 pulmonary artery sling, the carina is normally located at the T4–T5 vertebral level with characteristic compression of the posterior aspect of the trachea, right main bronchus, and anterior aspect of the esophagus.

In type 2 pulmonary artery sling, the carina is located relatively low in the chest, at the T6 level, and is associated with congenital long-segment tracheal stenosis and an inverted T-shaped carina, where the main bronchi assume a horizontal course. A bridging bronchus is sometimes present.

Contrast-enhanced MDCT of the chest usually yields sufficient diagnostic information by depicting the origin and course of the vessel, helping to differentiate it from other vascular anomalies and collateral arteries in the mediastinum. It also can be used to assess the central airways for coexisting anomalies. Two-dimensional or 3D reconstructions can be used as road maps for surgical planning. Treatment includes reimplantation of the left main pulmonary artery and surgical correction of the trachea if needed.

Suggested Readings

Lee EY, Boiselle PM, Cleveland RH. Multidetector CT evaluation of congenital lung anomalies. Radiology 2008; 247:632–648

Yildirim A, Karabulut N, Dogan S, Herek D. Congenital thoracic arterial anomalies in adults: a CT overview. Diagn Interv Radiol 2011; 17:352–362

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