Scimitar syndrome, also known as hypogenetic lung syndrome, is characterized by a hypoplastic lung that is drained by an anomalous pulmonary vein into the systemic venous system. It is a type of partial anomalous pulmonary venous return and is one of the several findings in congenital pulmonary venolobar syndrome.
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Epidemiology
Associations
congenital heart disease: e.g. ASD, VSD, tetralogy of Fallot, patent ductus arteriosus
ipsilateral diaphragmatic anomalies: e.g. accessory diaphragm, diaphragmatic hernia
vertebral anomalies: e.g. hemivertebrae 4
genitourinary tract abnormalities 4
Clinical presentation
Infants present with signs of heart failure, which may be due to associated congenital heart disease 13. Adults are most frequently asymptomatic but may have recurrent pulmonary infection or dyspnea on exertion.
Pathology
It is essentially a combination of pulmonary hypoplasia and partial anomalous pulmonary venous return (PAPVR). It almost exclusively occurs on the right side.
Haemodynamically, there is an acyanotic left-to-right shunt. The anomalous vein usually drains into the:
inferior vena cava: most common
In some variants, the abnormal lung segment may receive arterial blood supply from the aorta or its branches 1,4,11,12. Some cases may show the anomalous systemic arteries supplying an area of associated pulmonary sequestration 11.
Radiographic features
The diagnosis is made by transthoracic or transesophageal echocardiography, angiography, or by CT or MR angiography.
Plain radiograph
Chest radiographic findings are that of a small, hypoplastic 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). The right heart border may be blurred 16.
Treatment and prognosis
Surgical correction should be considered in the presence of significant left-to-right shunting and pulmonary hypertension. This involves the creation of an interatrial baffle to redirect the pulmonary venous return into the left atrium. Alternatively, the anomalous vein can be re-implanted directly into the left atrium.
Complications
The presence of a left-to-right shunt may lead to the development of pulmonary hypertension and Eisenmenger phenomenon.
History and etymology
Anomalous pulmonary venous drainage was first described in 1836 by Cooper and Chassinat. In 1949, Dotter et al. first described the radiological signs of Scimitar syndrome. Halasz et al. first used the word "Scimitar" in 1956 2. The term "Scimitar syndrome" was first given and described by C A Neill et al. in 1960 5.
Differential diagnosis
General imaging differential considerations include:
right middle lobe atelectasis (on AP plain radiograph)
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