Scimitar syndrome

The classic definition of the scimitar syndrome is a triad of hypoplasia of the right lung with anomalous venous drainage and a systemic arterial supply of a variable degree. We report a case in which a scimitar-shaped anomalous vein was observed on the plain chest radiograph, but subsequently a pulmonary angiogram showed that it drained normally into the left atrium.

Although classic description of the scimitar syndrome is the triad of hypoplasia of the right lung with anomalous venous drainage and systemic arterial supply of variable degree,[1] some authors define the syndrome wholly by the characteristic radiologic aspect of the anomalous vein.[2] We describe a case of a partially hypoplastic right lung with arterial supply from the aorta, and with a scimitar vein draining into the left atrium.

CASE REPORT

A 27-year-old woman was referred to us for investigation of an abnormal chest radiograph and a history of episodes of hemoptysis for 1 year. Physical examination showed a healthy looking woman with no cyanosis or finger clubbing. The thorax was symmetrical, and the heart and the breath sounds were normal. The chest radiograph disclosed a slightly reduced right lung, and a scimitar sign as a curvilinear vascular shadow running parallel to the right heart border (Fig 1). The lung scan showed a slight decrease in perfusion to the base of the right lung.

The right pulmonary angiogram revealed a normal arterial distribution except for the absence of pulmonary artery supply to the basal posterior segment. The venous phase disclosed a normal drainage of the upper zone into the left atrium. The anomalous vein drained the lower and middle zones, entering the left atrium together with the upper lobe vein (Fig 2). The left pulmonary circulation was normal. An anomalous artery was shown originating from the abdominal aorta below the diaphragm, supplying the right basal posterior area, which also drained through the pulmonary anomalous vein. A cardiac catheterization done ten years previously, when the patient was asymptomatic, showed normal oxygen saturation data without shunts.

DISCUSSION

Hypogenetic lung syndrome is a term used to describe abnormal development of the right lung characterized by a malformed lung, anomalous venous return into the inferior vena cava, and abnormal arterial supply commonly from the systemic circulation.[1] Because the anomalous vein is considered to resemble a sword, or scimitar, the scimitar syndrome is a frequently used synonym.

In about half of the cases, the size of the right pulmonary artery is minimally reduced; in some cases it can be severely reduced. Systemic supply is almost always present if looked for and may be derived from the thoracic aorta or from below the diaphragm.

Variations within the syndrome frequently are encountered. Since some authors define the syndrome just by the aspect of the anomalous vein, there are many cases reported as scimitar syndrome which do not fit in the original description of the hypogenetic lung syndrome. Among these variants, one very rarely described is the connection of the anomalous vein with the left atrium.[3,4]

In the case we report, the chest radiograph disclosed a scimitar vein, which was shown to drain to the left atrium rather than the inferior vena cava at angiography. In our patient, the lung drained by the abnormal vein had a systemic arterial supply.

What should we call this patient's anomaly?

This is not a classic case of scimitar syndrome because the drainage of the anomalous vein was not to the systemic venous system. In bronchopulmonary sequestration, the abnormal lung tissue has no normal connection to the bronchial tree and usually forms a radiographic density which is evidenced on the chest radiograph.[5,6] Derksen[7] and Burrows et al[8] would name it a "sequestration spectrum." Patridge et al[6] recently introduced the term "dysmorphic lung" to describe complex congenital malformation which involves abnormal vascular morphology and disordered growth of the lung. Panicek et al[9] stressed that pulmonary developmental anomalies exist as a continuum, often frustrating our attempts to classify them.

This case demonstrates that the presence of a scimitar vein on the chest radiograph does not necessarily indicate that the patient has the classic scimitar syndrome. Since the scimitar vein is so distinct, we propose that the definition of the scimitar syndrome be expanded to include patients such as ours. Considering that in most cases an angiographic study is not ordered because the patient is usually asymptomatic, the diagnosis of scimitar syndrome should be based solely on the chest radiograph image. However, since there is such a considerable overlap between the pulmonary developmental anomalies that may be associated with the scimitar syndrome, a complete angiographic study is mandatory in symptomatic patients, particularly when a surgical procedure is considered.

REFERENCES

[1] Neill CA, Ferenez C, Sabiston DC, Sheldon H. Bull Johns Hopkins Hosp 1960; 107:1-21

[2] Bessolo RJ, Maddison FE. Scimitar syndrome: a report of a case with unusual variations: AJR 1968; 103:572-76

[3] Morgan JR, Forker AD. Syndrome of hypoplasia of the right lung and dextroposition of the heart: "scimitar sign" with normal pulmonary venous drainage. Circulation 1971; 43:27-30

[4] Kanemoto N, Sugiyama T, Hirose S, Goto Y. A case with pseudo-scimitar syndrome: "scimitar sign" with normal pulmonary venous drainage. Jpn Circ J 1987; 51:642-46

[5] Currarino G, Williams B. Causes of congenital unilateral pulmonary hypoplasia. Paediatr Radiol 1985; 15:19-24

[6] Partridge JB, Osborne JM, Slaughter RE. Scimitar etcetera--the dysmorphic right lung. Clin Radiol 1988; 39:11-19

[7] Derksen OS. Scimitar syndrome and pulmonary sequestration: pulmonary anomalies with persistent embryonic communications between the pulmonary and systemic circulation. Radiol Clin 1977; 46:81-93

[8] Burrows PE, Freedom RM, Rabinovitch M, Moes CAF. The investigations of abnormal pulmonary arteries in congenital heart disease. Radiol Clin North Am 1985; 23:689-717

[9] Panicek DM, Heitzman ER, Randall PA, Groskin SA, Chew FS, Lane EJ Jr, et al. The continuum of pulmonary developmental anomalies. Radiographics 1987; 7:747-72

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