Scimitar syndrome

Associate Editor-in-Chief: Keri Shafer, M.D. [mailto:kshafer@bidmc.harvard.edu]

Synonyms and related keywords: Venolobar syndrome, hypogenetic lung syndrome.

Overview
Scimitar syndrome (a variant of Partially Anomalous Pulmonary Venous Return or PAPVR) is a rare congenital heart defect is characterized by a hypoplastic lung that is drained by an anomalous vein into the systemic venous system. It is essentially a combination of pulmonary hypoplasia and partial anomalous pulmonary venous return. It almost exclusively occurs on the right side. The hemodynamics are that of an acyanotic left to right shunt. The anomalous vein most commonly drains into the IVC, right atrium or portal vein. The lung is frequently perfused by the aorta, but the bronchial tree is still connected and thus the lung is not sequestered. CXR findings are that of a small lung with ipsilateral mediastinal shift, and in one third of cases the anomalous draining vein may be seen as a tubular structure paralleling the right heart border in the shape of a Turkish sword (“scimitar”). Scimitar syndrome is associated with congenital heart disease, ipsilateral diaphragmatic anomalies and vertebral anomalies.

Presentation
The anomalous venous return forms a curved shadow on chest x-ray such that it resembles a scimitar. This is called the Scimitar Sign. Associated abnormalities include right lung hypoplasia with associated dextrocardia, pulmonary artery hypoplasia and pulmonary arterial sequestration.

Diagnosis
The diagnosis is made by transthoracic or transesophageal echocardiography, angiography, and more recently by CT angiography or MR Angiography.

Treatment
Surgical correction should be considered in the presence of significant left to right shunting (Qp:Qs ≥ 2:1) and pulmonary hypertension. This involves creation of an inter-atrial baffle to redirect the pulmonary venous return into the left atrium. Alternatively, the anomalous vein can be re-implanted directly into the left atrium.