Scimitar syndrome

A case of a rare partial anomalous pulmonary venous return of the right upper lobe into the superior vena cava is reported. Multiple three-dimensional image reconstructions in association with spiral CT are used in the aim of clarifying this abnormality of pulmonary venous drainage. (CHEST 1995; 108:1743-45)

ASD=atrial septal defect; 3D=three-dimensional; PAPVR=partial anomalous pulmonary venous returns; SCT=spiral CT; SVC=superior vena cava

Key words: concomitant cardiac diseases; partial anomalous pulmonary venous return (PAPVR); scimitar syndrome; spiral computed tomography (SCT); three-dimensional (3D) image reconstructions; vena cava superior

Partial anomalous pulmonary venous return (PAPVR) is a dysgenesis in which the embryonic pulmonary venous plexus does not anastomose to the primitive sinus venosus. As a result, abnormal communications between the portions of the pulmonary venous plexus and the cardiac, cardinal, or omphalomesenteric venous system persist. We report a case in which the diagnosis of a PAPVR was initially suggested by a chest radiograph. An abnormal venous drainage to the superior vena cava (SVC) then was confirmed by spiral CT (SCT) of the chest. Three-dimensional (3D) reconstructions allowed a better understanding of the anomalous drainage due to the fact that images can be made angular and rotated on the screen of the workstation.[1] To our knowledge, this report is the first 3D representation of a PAPVR published in the literature.

CASE REPORT

A 45-year-old woman underwent an excision of a malignant melanoma located on her back. A chest radiograph revealed a curved vessel-like density, in the upper portion of the right lung, which was suspected of being a PAPVR. Further investigation with SCT was achieved and 60 1-mm-thick native sections were obtained from the region of interest at 120 kV and 100 milliampere second at full end-inspiratory position (Fig 1). Images were processed on a 3D workstation (Advantage Windows 1.2 GE Medical System; Milwaukee). Pulmonary vessels were extracted from the lung parenchyma with a threshold at -500 Hounsfield units. The thoracic wall was removed manually. A surface rendering algorithm was used for 3D visualization (Fig 2).

Both axial sections and 3D reconstructions clearly showed that the PAPVR arose from 3 vessels. These originated from the anterior, apical, and posterior segments of the right upper lobe and joined just before entering the lateral aspect of the SVC at the level of the carina (Fig 1). No other abnormality was observed on the SCT examination. The patient was discharged without any treatment for this asymptomatic PAPVR.

Discussion

Frequency of PAPVR is about 0.4 to 0.7%[2-6] in autopsy series of patients with congenital heart disease, and involvement of the right lung is shown to be twice that of the left lung. Concomitant cardiac diseases may be found, commonly an atrial septal defect (ASD) of the sinus venosus type. Ninety percent of patients with PAPVR draining into the SVC or the right atrium have an associated ASD, whereas the same malformation can only be present in 15% of PAPVR to the inferior vena cava.[3] Apart from ASD, additional cardiac malformations occur in about 20% of patients, including ventricular septal defect and Fallot's tetralogy.[4]

In the absence of associated anomalies, patients remain asymptomatic, thus explaining the difficulty in knowing the real incidence of PAPVR. Physiologic disturbances depend on the number of anomalous veins, their site of connection, the presence of concomitant diseases, and the state of the vascular bed.[4] Right cardiac failure, with progressive fatigue, dyspnea, a fixed secondary heart sound, right atrial and ventricular hypertrophy, and right axis deviation with incomplete right branch block is a common alteration, related to the severity of the associated ASD.[4]

Chest radiographs in patients with PAPVR are not always specific, but when positive, they typically show a curvilinear vascular structure in the mid or upper lung directed toward the right atrium, the SVC, or the azygos vein.[4] A verticaloriented crescentic vascular structure in the lower area of the right lung represents a PAPVR to the inferior vena cava, the so-called scimitar syndrome.[6] Symptoms and radiologic presentation of this entity depend on the degree of associated conditions.

Dextroposition of the heart and mediastinal shift to the right are related to right lung hypoplasia. The latter is proportional to the reduced size of the right pulmonary artery found in about half the cases.[7] Pulmonary parenchymal Iterations (unusual segmentation) and tracheal or bronchial stenosis may be found as well as bronchiectasis. Recurrent pulmonary infections can then be explained on this anatomic base. Congenital heart disease is present in about 25% of the patients.[7] Most commonly, patients suffer from a second ASD. The radiologist also may search for associated diseases like eventration of the right half of the diaphragm and hemivertebra.

Therapeutic decision-making in PAPVR depends on two factors: the hemodynamic situation and the associated cardiac malformations. if the pulmonary flow to systemic flow ratio is less than 1.5, patients can be followed up until adolescence. However, patients presenting with cardiac malformations should undergo surgery after diagnosis.[8]

SCT with 3D reconstruction was useful in our case to confirm PAPVR and may become the modality of choice for imaging asymptomatic vascular pulmonary anomalies. However, angiographic examination may be necessary for specific treatment planning, such as surgical correction of a vascular anomaly. MRI and angiography might give useful anatomical and functional information through flow quantification in the PAPVR.

[Figure 1-2 ILLUSTRATION OMITTED]

REFERENCES

[1] Remy J, Remy-Jardin M, Giraud F, et al. Angioarchitecture of pulmonary arteriovenous malformations: clinical utility of three-dimensional helical CT. Radiology 1994; 191(3):557-64 [2] Kalke B, Carlson R, Ferrlici R, et al. Partial pulmonary anomalous venous connection. Am J Cardiol 1967; 20:91-101 [3] Schuhmacker HB, Judd D. Partial pulmonary anomalous venous return with reference to drainage into inferior vena cava and into intact atrial septum. J Cardiovasc Surg 1964; 5:271-78 [4] Friedman WF. Partial anomalous pulmonary venous connection. In: Braunwald E. Heart disease: a textbook of cardiovascular medicine. Philadelphia: WB Saunders, 1992; 951 [5] Posniak H, Dudiak CM, Olson MC. Computed tomography: diagnosis of partial anomalous pulmonary venous drainage. Cardiovasc Intervent Radiol 1993; 16:319-20 [6] Olson MA, Becker GJ. The scimitar syndrome: CT findings in partial anomalous pulmonary venous return. Radiology 1986; 159:25-6 [7] Godwin JD, Tarver RD. Scimitar syndrome: four new cases examined with CT. Radiology 1986; 159:15-20 [8] Van Meter C, LeBlanc JG, Culpepper WS, et al. Partial anomalous pulmonary venous return. Circulation 1990; 82(suppl): 195-98

(*) From the Department of Radiology, University Hospital CHUV, Lausanne, Switzerland. Reprint requests: Dr. Schnyder, Department of Radiology, University Hospital CHUV, 1011 Lausanne, Switzerland

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