The Egyptian Journal of Radiology and Nuclear Medicine (2011) 42, 381–387
Egyptian Society of Radiology and Nuclear Medicine
The Egyptian Journal of Radiology and Nuclear Medicine www.elsevier.com/locate/ejrnm www.sciencedirect.com
REVIEW
Scimitar syndrome: MDCT imaging revisited Sameh El-Medany, Khaled El-Noueam *, Ayman Sakr Department of Radiology, Alexandria University, Egypt Received 10 April 2011; accepted 30 August 2011 Available online 29 September 2011
KEYWORDS
Abstract Scimitar syndrome refers to a form of anomalous pulmonary venous drainage which implies partial or total failure of the pulmonary veins to reach the left atrium. Aim: To emphasize the role of MDCT in the diagnosis of Scimitar syndrome. Patients and methods: We presented MDCT imaging findings in three patients with Scimitar syndrome. Results: MDCT revealed anomalous arterial blood supply from abdominal aorta to right lower lung lobe and anomalous venous drainage into infradiaphragmatic IVC, hypoplastic right pulmonary artery and hypoplastic right lung as well as atrial septal defect and bronchial diverticulum. Conclusion: MDCT is essential investigation in Scimitar syndrome.
Scimitar syndrome; MDCT
Ó 2011 Egyptian Society of Radiology and Nuclear Medicine. Production and hosting by Elsevier B.V. Open access under CC BY-NC-ND license.
Contents 1. 2. 3. 4.
Introduction . . . . . . . Patients and methods. Results . . . . . . . . . . . Discussion . . . . . . . . References. . . . . . . . . .
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* Corresponding author. Address: Faculty of Medicine, Alexandria University, Egypt. E-mail address:
[email protected] (K. El-Noueam). 0378-603X Ó 2011 Egyptian Society of Radiology and Nuclear Medicine. Production and hosting by Elsevier B.V. Open access under CC BY-NC-ND license.
Peer review under responsibility of Egyptian Society of Radiology and Nuclear Medicine. doi:10.1016/j.ejrnm.2011.08.004
Production and hosting by Elsevier
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1. Introduction Scimitar syndrome is a rare association of congenital cardiopulmonary anomalies, and first described in 1836 [1]. The syndrome is a form of anomalous pulmonary venous drainage which implies partial or total failure of the pulmonary veins to reach the left atrium. Instead, pulmonary venous drainage is anomalously connected to the systemic vein/s, typically to the superior vena cava or inferior vena cava or directly to the right atrium [2].
382 Although radiographs play a role in the incidental detection and initial imaging evaluation in patients with clinical suspicion of congenital lung anomalies, computed tomography is frequently required for the confirmation of diagnosis, further characterization, and preoperative evaluation in the case of surgical lesions. Computed tomography (CT) has broadened the imaging of lung anatomy by offering various reformation techniques, which demonstrate the anatomy down to the subsegmental level. These reformation techniques include multiplanar reconstruction, shaded-surface display (SSD), minimum-intensity projection, maximum-intensity projection, sliding thin slab imaging, volume rendering and virtual bronchoscopy [3]. The aim of the work was directed to emphasize the role of the multidetector computed tomography (MDCT) in Scimitar syndrome. 2. Patients and methods We present the CT imaging findings in three patients with Scimitar syndrome. All patients had multi-detector row CT of the chest after IV contrast injection. Examinations were performed on GE Light speed 4 scanner and Siemens Emotion 6 MDCT. Scanning parameters were: Volumetric High-spatial-frequency kernel algorithm. Slice thickness: 1.25 mm. Table speed for volumetric HRCT to enable the least cycles of breath-holds as possible. Tube rotation: 0.6–0.9 s (0.75 s). Detector Collimation 1 mm. Helical mode (volumetric HRCT). Field of view (FOV) for small, medium and large patients. kVp and mA per slice: 80–100 kVp and approximately 200–240 mA, although lower doses (60–90 mAs) were used with pediatric and small patients or those receiving serial HRCT scans. For multiplanar reconstruction; scans were performed to cover the root of the neck down to the level of the adrenal glands. The thin slices were sent to the workstation to be viewed in the axial, sagittal and coronal planes as well as for displaying volume rendering. 3. Results The first patient (Fig. 1) was an eight year old female patient where CT imaging showed hypoplastic right pulmonary artery, anomalous arterial blood supply from the abdominal aorta to the right lower lung lobe and anomalous venous drainage into infradiaphragmatic inferior vena cava (Scimitar vein). The second patient (Fig. 2) was a five month old female patient showing hypoplastic right lung with associated atrial septal defect, hypoplastic right pulmonary artery, anomalous arterial blood supply to the lower lung lobe from abdominal aorta and anomalous venous drainage into infradiaphragmatic inferior vena cava. The third patient (Fig. 3) was a two month old male patient. CT imaging revealed hypoplastic right lung associated with bronchial diverticulum from the right lower lobe bronchus, anomalous arterial blood supply to the right lower lobe from abdominal aorta and anomalous Scimitar vein draining into infradiaphragmatic IVC. 4. Discussion Scimitar syndrome is a rare, but well characterized disease accounting for 0.5–1% of all CHD [4]. The term ‘Scimitar syndrome’ was coined by Neill et al., with reference to the characteristic appearance of the anomalous right pulmonary venous confluence on the X-ray chest. The vein is said to resemble a
S. El-Medany et al. curved Turkish sword called a ‘Scimitar’. The X-ray appearance is referred to as the ‘Scimitar Sign’. The syndrome is characterized by partial anomalous pulmonary venous connection of the right pulmonary veins, via the confluence to the infra-diaphragmatic inferior vena cava, above the drainage site of the hepatic veins. There is usually no obstruction to pulmonary venous flow. Rare cases of connection to the hepatic veins or to the portal vein have been documented [4]. The other components of the syndrome include hypoplasia of the lower lobe of the right lung, hypoplasia of the right pulmonary artery or its lower branch, abnormalities of tracheobronchial architecture, abnormal lobar architecture and sequestration of the right lower lobe (vascular supply from a branch of the aorta). Intact inter-atrial septum is very rare and a sinus venosus form of atrial septal defect is almost always present [4,5]. Two varieties have been described. The infantile form presents in infancy or early childhood due to other associated cardiac anomalies like Fallot’s tetralogy, coarctation of the aorta, patent ductus arteriosus and ventricular septal defect. The adult form, where the syndrome is detected after the first year of life, presents late or may remain totally asymptomatic and is not associated with other cardiac anomalies [4]. Scimitar syndrome occurs as the result of abnormal development of the right lung bud in the early embryogenesis. It tends to most frequently involve the right lung, for unknown reasons, with rare reports of the left lung involvement. It occurs more commonly in females, with occasional familial occurrence. The clinical presentation is quite variable, being asymptomatic to florid heart failure. Dupis et al. [5], in their review of 122 adult patients, showed recurrent pneumonia as the most common presentation followed by exertional breathlessness, deformity of thorax and hemoptysis in descending order of frequency. In the adult form, clinical examination may be entirely normal. ECG may show right ventricular strain. Echocardiography, apart from identifying associated anomalies, may help in establishing the diagnosis; however, can miss 33% of patients [6]. CT, cardiac catheterization, and magnetic resonance imaging with three-dimensional magnetic resonance angiography are more rewarding [7]. One-quarter of the cases are symptomatic in the newborn, presenting as respiratory or cardiac failure needing corrective surgery. CT has the advantages of easy availability and very short scanning times. Radiologists have developed a facility for using CT in vascular imaging. Contrast material – enhanced helical CT allows the precise timing necessary for accurate extracardiac arterial and venous vascular imaging. Multiplanar reformation is currently readily available, decreasing the inherent disadvantage of the CT image acquisition exclusively in the transaxial plane. The drawbacks of CT include patient exposure to ionizing radiation and the risks of iodinated contrast material. Adjustment of specific technical factors has been shown to minimize the radiation dose in children undergoing CT. Such adjustment includes setting the lowest diagnostic tube current according to the patient weight (range, 40–140 mA for chest CT). In addition, doubling the pitch reduces radiation dose by half. A practical standard pitch for single-detector row helical CT in children is 1.5:1. The decision to image with CT versus MR imaging should be based on institutional equipment, scheduling, and availability as well as the patient’s ability to cooperate. The need to tailor the examination to answer the specific questions being asked may also guide the choice of CT versus MR imaging [8–11].
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Figure 1 An eight year old female patient with congenital venolobar or Scimitar syndrome. (a) Axial CT image showing hypoplastic right pulmonary artery (red arrow). (b) Axial CT image with lung window/level showing hypoplastic right lung. (c) Axial CT image at a lower level showing anomalous arterial blood supply from the abdominal aorta to the right lower lung lobe (blue arrow). (d) Coronal reformatted CT image showing anomalous venous drainage into infradiaphragmatic inferior vena cava (green arrow). (e) VR reconstructed CT image showing the previously mentioned anomalous arterial supply and venous drainage (Scimitar vein).
The MDCT studies in the three patients with congenital venolobar pulmonary or Scimitar syndrome showed the characteristic components of anomalous arterial blood supply from the abdominal aorta without sequestration and anomalous pulmonary venous drainage into infradiaphragmatic inferior vena cava (Scimitar vein), right pulmonary artery hypoplasia and right sided lung hypoplasia. Woodring et al. [12] reported that the most common components of the congenital pulmonary venolobar syndrome are hypogenetic lung and anomalous pulmonary venous return. Ko et al. [13] added that isolated anomalous systemic supply to the lower lobes without
bronchial abnormality is also reported. Morgan et al. [14] also clarified that in patients in whom hypoplastic lung tissue is present, the proximal portion of the ipsilateral pulmonary artery is absent; however, the peripheral pulmonary arteries are present. Systemic collateral circulation to the peripheral pulmonary arteries occurs and most often arises from the bronchial arteries. With time, large transpleural collateral vessels to the intercostal arteries may also develop. According to Felson et al. [15], the anomalous pulmonary vein most often drains into the inferior vena cava below the right hemidiaphragm. Less commonly partial anomalous pulmonary venous
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S. El-Medany et al.
Figure 2 A five month old female patient with congenital venolobar syndrome showing the following criteria. (a) Axial CT image showing hypoplastic right lung with associated atrial septal defect (yellow arrow). (b) Axial CT image showing hypoplastic right pulmonary artery (red arrow). (c and d) Coronal reformatted CT 6 images showing anomalous arterial blood supply to the lower lung lobe from abdominal aorta (blue arrow) and anomalous venous drainage into infradiaphragmatic inferior vena cava (yellow arrow). (e) VR reconstructed image showing the previously mentioned anomalous arterial supply and venous drainage (blue and yellow arrows) as components of Scimitar syndrome.
return drains into the suprahepatic portion of the inferior vena cava, hepatic veins, portal vein, azygous vein, coronary sinus, or right atrium. Drainage of the anomalous vein into the suprahepatic portion of the inferior vena cava or right atrium may be a clue to the associated congenital interruption of the intrahepatic portion of the inferior vena cava. When partial anomalous pulmonary venous return drains to a systemic vein or to the right atrium, there is a left-to-right shunt, which is
usually asymptomatic unless the shunt is 2:1 or greater. On occasion, the partial anomalous pulmonary venous return drains to the left atrium and when it occurs; the anomalous vein is called a ‘‘meandering’’ pulmonary vein. Berrocal et al. [16] addressed that infants present early with scimitar syndrome, particularly when they have coexistent congenital heart disease or systemic arterial supply to the right lung. This group of patients statistically has a higher morbidity
Scimitar syndrome: MDCT imaging revisited
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Figure 3 A two month old male patient with Scimitar syndrome. (a) Coronal reformatted minIP CT image showing hypoplastic right lung associated with bronchial diverticulum from the right lower lobe bronchus (blue arrow). (b) Axial CT image showing hypoplastic right lung. (c) Axial MIP CT image showing anomalous arterial blood supply to the right lower lobe from abdominal aorta (yellow arrows). (d) Axial MIP CT image showing anomalous venous drainage into infradiaphragmatic inferior vena cava (yellow arrows). (e) Coronal reformatted MIP image showing the anomalous Scimitar vein draining into infradiaphragmatic IVC (yellow arrows).
and mortality, and is more likely to develop pulmonary hypertension. Multiple factors contribute to the development of pulmonary hypertension, including the left-right shunts caused by the scimitar vein, septal defect, and the aberrant systemic arterial supply. Some patients, however, may remain asymptomatic or present in adult life with mild exertional dyspnea or recurrent lower respiratory tract infections. Huddleston et al. [17] added that infants typically manifest congestive heart failure secondary to right heart volume overload due to drainage
of the oxygenated blood directly into the inferior vena cava or right atrium instead of left atrium. Diagnosis of Scimitar syndrome is made by examining the X-ray of the chest. While echocardiography can demonstrate the atrial septal defect and absence of right pulmonary venous drainage into the left atrium, detailed anatomic evaluation of the anomalous channel requires invasive angiocardiography, multidetector CT angiocardiography or MR angiocardiography. [18] We used MDCT angiocardiography to demonstrate
386 the anomalous vein and to obtain accurate anatomical information non-invasively. Echocardiography and angiography are traditionally used to diagnose congenital heart disease. Echocardiography with Doppler performs well in defining intracardiac anomalies and in estimating hemodynamics. However, it is limited by a small field of view, a variable acoustic window, inability to penetrate air and bone, and difficulty in delineating extracardiac vascular structures in their entirety. Cardiac catheterization and angiography is an invasive modality that yields important hemodynamic data while clearly defining the anatomy in vessels that are accessible to catheterization. However, angiography often gives only indirect information regarding venous connections and arterial anatomy distal to high-grade stenosis or atresia. It also uses high doses of ionizing radiation and is limited by the risks inherent to iodinated contrast material. Therefore, magnetic resonance imaging and computed tomography play a valuable role in bridging the gaps created by echocardiography and angiography, specifically with regard to extracardiac arterial and venous anatomy and connections in patients with congenital heart disease. MR imaging and CT can assist in making appropriate decisions in evaluation of and surgical planning for patients who have previously undergone surgical or other interventional cardiac procedures, especially if vascular access is difficult or undesired [19,20]. The direct multiplanar image capability of MR imaging allows precise depiction of the complex and often unexpected cardiac and extracardiac arterial and venous morphologies present. MR imaging also has the advantage of not exposing the patient to ionizing radiation. Rapid image acquisition sequences such as single-shot echo-planar imaging and half-Fourier single-shot turbo spin-echo imaging are continuing to evolve. These advances make MR imaging more practical for sick young patients and lessen the duration of sedation. MR imaging has proved to be effective in diagnosis of coarctation of the aorta, aortic arch anomalies with vascular rings, pulmonary arterial and venous connections, and complex univentricular lesions [21,22]. Options for repair of Scimitar syndrome depend on the anatomy [23]. The first method entails the creation of an internal conduit within the right atrium to conduct right pulmonary blood from its entrance in the inferior vena cava to the left atrium through the atrial septal defect, which may or may not be enlarged. The second technique entails the disconnection of the anomalous vein from its connection with the inferior vena cava and reimplantation higher up in the right atrium, with a baffle connecting the vein to the left atrium. The third technique consists of disconnecting the anomalous vein form the junction with the inferior vena cava and connecting it to the rightmost aspect of the left atrium, which is ‘bare’ (due to no connection of the right pulmonary veins). The long term results of the correction performed in childhood or early adult life in this disorder are generally good [23]. Brown et al. [24] reported that the direct reimplantation of the scimitar vein into the left atrium may be feasible in some patients, avoiding cardiopulmonary bypass. Although repair of the anomalous venous return or ligation of collaterals is the procedure of choice, pneumonectomy has also shown similar early and late results. Surgery is indicated when the right-to-left shunt is >2:1 [23]. Sometimes patients present with an incidental radiological finding with no symptoms and require no intervention.
S. El-Medany et al. Various imaging modalities contribute diagnostic information in patients with congenital heart disease. CT and MR imaging are especially useful in demonstrating extracardiac anatomy. Echocardiography continues to be the preferred modality for imaging intracardiac anatomy and hemodynamics. The 64-slice CT which is a minimally invasive examination with fast scanning is suitable for neonates and infants. The combined use of advanced postprocessing graphic workstations, allows improved delineation of the complex and variable anatomic abnormalities seen in patients with congenital pulmonary venolobar syndrome. A thorough preoperative understanding of the complex cardiovascular anatomy facilitates a directed and prepared surgical approach. In this article, we emphasized the importance of MDCT in delineating the spectrum of findings in patients with congenital pulmonary venolobar syndrome. References [1] Cooper G. Case of malformation of the thoracic viscera consisting of imperfect development of the right lung and transposition of the heart. London Med Gas 1936;18:600–1. [2] Grech V, Xuereb R, Xuereb M, Manche A, Schembri K, DeGiovanni JV. Late presentation and successful treatment of classical scimitar syndrome. Images Paediatr Cardiol 2003;16:49–62. [3] Lee EY, Boiselle PM, Cleveland RH. Multidetector CT evaluation of congenital lung anomalies. Radiology 2008;247:632–48. [4] Sehgal F, Loughran-Fowlds A. Scimitar syndrome. Indian J Paediatr 2005;72:249–51. [5] Dupis C, Haraf LAC, Breviere GM, Abou P. ‘‘Infantile’’ form of scimitar syndrome with pulmonary hypertension. Am J Cardiol 1993;71:1326–30. [6] Wong ML, McCrindle BW, Mota C, Smallhorn JF. Echocardiographic evaluation of partial anomalous pulmonary venous drainage. J Am Coll Cardiol 1995;26:503–7. [7] Huebsch P, Neuhold A, Mayr H, Glogar D. Anomalous pulmonary venous drainage shown by duplex sonography, computed tomography, and plain radiography. Thorax 1989;44:63–5. [8] Konen Ei, Raviv-Zilka L, Cohen RA, Epelman M, BogerMegiddo I, Bar-Ziv J, Hegesh J, Ofer A, Konen O, Katz M, Gayer G, Rozenman J. Congenital pulmonary venolobar syndrome: spectrum of helical CT findings with emphasis on computerized reformatting. Radiographics 2003;23:1175–84. [9] Yamanaka A, Hirai T, Fujimoto T, Hase M, Noguchi M, Konishi F. Anomalous systemic arterial supply to normal basal segments of the left lower lobe. Ann Thorac Surg 1999;68:332–8. [10] Godwin JD, Tarver RD. Scimitar syndrome: four new cases examined with CT. Radiology 1986;159:15–20. [11] Rappaport DC, Herman SJ, Weisbrod GL. Congenital bronchopulmonary diseases in adults: CT findings. AJR Am J Roentgenol 1994;162:1295–9. [12] Woodring JH, Howard TA, Kanga JF. Congenital pulmonary venolobar syndrome revisited. Radiographics 1994;14:349–69. [13] KO SF, Ng SH, Lee TY. Anomalous systemic arterialization to normal basal segments of the left lower lobe: helical CT and CT angiographic findings. J Comput Assist Tomogr 2000;24:971–6. [14] Morgan PW, Foley DW, Erickson SJ. Proximal interruption of a main pulmonary artery with transpleural collateral vessels: CT and magnetic resonance appearances. J Comput Assist Tomogr 1991;15:311–3. [15] Felson B. Chest roentgenology. Philadelphia: Saunders; 1973. [16] Berrocal T, Madrid C, Novo S, Gutie´rrez J, Arjonilla A, Go´mezleo´n N. Congenital anomalies of tracheobronchial tree, lung and mediastinum: embryology, radiology and pathology. Radiographics 2003;24:26–43.
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