Scimitar Syndrome: Experience With 6 Patients
Ranjith Baskar Karthekeyan, MD,
Richard Saldanha, MCh,
M Ranjith Sahadevan, MD,
Suresh KG Rao, MD,
Mahesh Vakamudi, MD,
Balakrishnan K Rajagopal, MCh
Sri Ramachandra Medical College and Research Institute Porur, Chennai, India
Ranjith Baskar Karthekeyan, MD, Tel: +91 44 24986880, Fax: + 91 44 24769033, Email: ranjithb73{at}gmail.com, Department of Cardiac Anesthesiology, Sri Ramachandra Medical College and Research Institute, No. 1 Ramachandra Nagar, Porur, Chennai – 116, India.
ABSTRACT
Scimitar syndrome is a rare congenital anomaly characterized by anomalous pulmonary venous drainage to the inferior vena cava, causing a left-to-right shunt. Six patients with scimitar syndrome were diagnosed in our hospital between 2002 and 2008. There were 4 girls and 2 boys; 4 < 5 kg in weight, 2 < 8 kg in weight. Scimitar syndrome was suspected in 5 cases because of dextroversion, and diagnosed by color Doppler echocardiography in all 6 when a scimitar vein was detected entering the inferior vena cava. Computed tomography confirmed the diagnosis in all patients. Two patients had horseshoe lung, 2 had a unilobar right lung, 1 had a hypoplastic right lung, and 1 had a hypoplastic right lower lobe. Three patients had severe pulmonary arterial hypertension, 2 had moderate pulmonary arterial hypertension, and one had normal pulmonary arterial pressure. All patients had lower respiratory tract infections, volume loss of the right lung, a normal or hyperinflated left lung, dextroversion of the heart, and scimitar arteries from the descending aorta. Pneumonectomy was performed in 3 patients, lobectomy in 1, ligation of anomalous vessels in 1, and 1 died before surgery.
Key Words: Heart Defects • Congenital • Hypertension • Pulmonary • Scimitar Syndrome
INTRODUCTION
Scimitar syndrome is a form of partial anomalous venous drainage, which is sometimes dramatically detected by plain chest radiograph in anteroposterior view. The descending pulmonary vein is visible as a curvilinear density along the right heart border, resembling the curved Turkish sword that gives the condition its name. Scimitar syndrome is also known as Halasz syndrome, mirror-image lung syndrome, hypogenetic lung syndrome, epibronchial right pulmonary artery syndrome, and vena cava-bronchovascular syndrome. The left lung is very rarely involved, for unknown reasons. The true incidence is not known because the syndrome may be undetected in asymptomatic patients who have not undergone chest radiography. It is also called venolobar syndrome if it is associated with pulmonary sequestration.1
PATIENTS AND METHODS
Six patients with scimitar syndrome were diagnosed in our hospital between 2002 and 2008. There were 4 girls and 2 boys. Four of them were under 5 kg in weight, and the other 2 were under 8 kg in weight. Details are summarized in Table 1
. Symptoms included delayed milestones, breathlessness, cyanosis, excessive sweating, poor weight gain, and recurrent lower respiratory infections. Although chest radiography is diagnostic of scimitar syndrome in older infants and children, we were able to discern the scimitar vein in only 2 of our patients. Scimitar syndrome was suspected in the others due to dextroversion, and diagnosed by color Doppler echocardiography and computed tomography in all 6 by detection of a scimitar vein entering the inferior vena cava (Figures 1–7). In addition, 2 patients had a horseshoe lung (Figure 5) and 2 had a unilobar right lung. Patient no. 5 was also found to have scoliosis (Figure 7). One patient had a hypoplastic right pulmonary artery (Figure 8) and hypoplastic right lung (Figure 9), and another had a hypoplastic right lower lobe only. Three patients had severe pulmonary arterial hypertension, 2 had moderate pulmonary arterial hypertension, and 1 had normal pulmonary arterial pressure. All patients had lower respiratory tract infections, volume loss of the right lung, normal or hyperinflated left lung, dextroversion of the heart, and scimitar arteries from the descending aorta.
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Figure 9. Computed tomography angiogram of patient no. 6 showing hypoplastic right lung and aberrant artery.
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RESULTS
Pneumonectomy was performed in 3 patients, lobectomy in 1, and ligation of anomalous vessels in 1. Patient no. 6 who had severe pulmonary arterial hypertension and sepsis on admission died after diagnosis and before surgery in the neonatal period. Another newborn died postoperatively after preoperative sepsis and severe pulmonary arterial hypertension. Operative procedures and follow-up are summarized in Table 2.
DISCUSSION
The first case report of anomalous pulmonary venous drainage into the inferior vena cava was published in 1836, and the condition was named scimitar syndrome in 1960 because of the curvilinear density along the right heart border on chest radiography, resembling a Turkish sword. Scimitar syndrome consists of various additional features apart from anomalous venous drainage, such as various degrees of hypoplasia of the right lung, systemic arteries supplying the right lung from the descending aorta, pulmonary artery and venous hypoplasia with pulmonary hypertension, and congestive cardiac failure. In horseshoe lung, both the lungs are fused at the posteroinferior segments behind the heart and/or in front of the esophageus.2 The finding of associated horseshoe lung is considered extremely rare, and only a few cases have been reported.3 In horseshoe lung, the right lung is connected by a bar of normal pulmonary tissue.3 All of the major anomalies reported to be associated with scimitar syndrome were present in our patients.
The syndrome has been described in 2 forms. The infantile form is diagnosed under 1 year of age and presents with severe respiratory distress, pulmonary hypertension, cardiac failure, failure to thrive, and recurrent respiratory infection; it is associated with a poor prognosis. The adult form is usually diagnosed after 1 year of age and is associated with less pulmonary hypertension and a smaller shunt. The shunt fraction is <50%, with normal pulmonary pressures in most cases, and patients lead a normal life without surgical correction.4 Most of our patients belonged to the infantile group. Half of the patients are asymptomatic or mildly symptomatic when the diagnosis is made, despite varying degrees of pulmonary hypoplasia and pulmonary hypertension.5 In our series, 5 of the 6 patients had moderate to severe pulmonary artery hypertension.
The scimitar-shaped vascular shadow represents the union of the pulmonary veins to form a common vessel that turns downwards, parallel to the right cardiac border, to join the inferior vena cava. Usually, there is a single vein, but there may be 2 that form a single trunk or enter the vena cava separately. This anomalous venous drainage is associated with abnormalities of both the bronchial tree and lung parenchyma, such as partial agenesis and hypoplasia. Two types of scimitar veins are usually recognized. One is a simple classic vein that runs from the middle of the right lung to the cardiophrenic angle. The other is a double-arched vein in the upper and lower lung zones, with ample drainage into the inferior vena cava.6 Three of our patients had a single anomalous vein draining form the right lower lobe into the inferior vena cava. One patient had all 3 pulmonary veins from the right lung forming a scimitar vein and draining into the inferior vena cava. Two patients had unilobar right lung with the entire drainage via the anomalous vein into the inferior vena cava. Another component of this syndrome is an aberrant systemic arterial supply to the lower lobe of the right lung. This may originate either in the abdominal or lower thoracic aorta. The aberrant arteries supply normal pulmonary segments. These aberrant arteries are similar to those observed in conditions such as intralobular or extralobular pulmonary sequestration.3 In our series, all patients had a large artery arising from the descending aorta, supplying the right lung directly.
The surgical management of scimitar syndrome is controversial, with no definite guidelines.4 The most effective surgical treatment is still not well established but may involve partial or total resection of the right lung or redirecting the abnormal vein into the left atrium. The best option available is a lobectomy but that is seldom possible. The indications for surgery include a large left-to-right shunt>50%, resulting in pulmonary hypertension and sequestrated lung.6 Lung resection is simpler and associated with less operative and postoperative morbidity. It does not measurably impair respiratory function.7 Najm and colleagues2 discouraged lung resection because of the long-term effects of causing scoliosis or producing chronic respiratory insufficiency, and because growth of hypoplastic lung may occur as late as 7 to 10 years of age; they also concluded that repair of the anomalous vein was not very successful.
Division of the systemic arteries along with medical therapy gives the best result for the more severe infantile form of scimitar syndrome. Isolated ligation and reimplantation of the anomalous vein in infancy has been unsuccessful due to thrombosis and anastomotic stenosis.7 Coil embolization of the scimitar artery and vein is also a well-documented option. Uthaman and colleagues8 performed embolization of the scimitar artery and vein in infancy as the treatment of choice, and resorted to surgical intervention in later life if needed. They showed variable reductions of the left-to-right shunt and pulmonary artery pressure with embolization in all the patients, with reasonable success. We considered coil embolization in one patient, but opted for surgical ligation. Reimplantation was not considered in our patients due to low weight, young age, and questionable outcomes in the literature. The indications to carry out lung resection in our series were weight <5 kg, severe pulmonary arterial hypertension, left-to-right shunt exceeding 50%, hypoplastic lung, sequestrated lung, recurrent respiratory tract infections when the other lung would also be compromised, and the entire drainage of the lung through a single vein that would be impossible to reroute due to small size.
ACKNOWLEDGMENTS
We sincerely thank Dr. Karthikeyan, Dr. Harish, Dr. Ramesh, Dr. Siva Muthukumar, Dr. Harsha, and Dr. Srinath for their help in preparing the manuscript.
REFERENCES
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Asian Cardiovasc Thorac Ann 2009;
17:266-271
© 2009 by SAGE Publications
DOI: 10.1177/0218492309104750
