The scimitar sign is characteristic of partial anomalous pulmonary venous drainage into the inferior vena cava (IVC). We encountered two variant cases of scimitar sign. In one case, the scimitar vein entered both the IVC and the left atrium (LA) without any intracardiac shunts. Surgical repair was made by simple ligation of the scimitar vein to correct the left to right shunt. Retrograde balloon occlusion angiography of the scimitar vein was diagnostic. In the other case, the scimitar vein showed a meandering course, and then drained into the LA without any connection with the IVC, and surgical intervention was not required.
Partial anomalous pulmonary venous drainage with return to the inferior vena cava (IVC) is a rare congenital cardiovascular anomaly. However, it is well-known because the radiographic appearance of the pulmonary vein descending along the right cardiac border presents a characteristic appearance, called the scimitar sign.[1-4] Although it has been stated that the diagnosis can be made easily from this sign,[2,3] this is not entirely correct. Two variant cases are described in this report. In one, the anomalous vein drained both the IVC and the left atrium (LA); in the other, it returned to the LA, showing a scimitar-like roentgenogram.
An 8-year-old girl was admitted to the hospital for evaluation of an abnormal shadow on a routine chest x-ray film. The physical examination was unremarkable except for the fixed splitting of the second sound, and a systolic ejection murmur heard in the anterior area of the chest. Frontal chest x-ray films (Fig 1) revealed an anomalous vessel coursing down along the border of the right side of the heart toward the diaphragm, which is the typical scimitar sign. The surface ECG was entirely normal. Cardiac catheterization revealed the step-up in oxygen saturation between the right atrium and the IVC with a pulmonary-to-systemic flow ratio of 1.92. Adequate communication between the anomalous vein and the LA was clearly demonstrated by balloon occlusion angiogram of the anomalous vein (Fig 2). Based on these findings, surgical repair via a right thoracotomy was done. At operation, a 10-mm in diameter anomalous vessel was found to pierce the diaphragm. It was ligated just above the diaphragm. The absence of lung engorgement indicated adequacy of the communication with the LA. The patient had an uneventful postoperative course, and cardiac catheterization 1 month later confirmed the absence of the left-to-right shunt.
A 28-year-old woman was referred to our hospital for evaluation of abnormal chest x-ray films. She had no history of respiratory illness or other diseases. Physical examination revealed a well-developed, healthy woman with normal ausculatory findings. Right pulmonary angiography revealed that the pulmonary vein, though it had an unusual appearance, normally entered the LA without any connection with the IVC (Fig 3), indicating no need for surgery.
The unique feature of partial anomalous pulmonary venous drainage with return to the IVC is that it presents a characteristic abnormal radiographic shadow, which descends along the right cardiac border, called the scimitar sign. Furthermore, it is also frequently complicated by hypoplasia of the right lung and cardiac deviation toward the right side of the body. Neill et al called these three findings the "scimitar syndrome." This syndrome also is associated with abnormal systemic blood supply to the right lung, abnormal bronchial anatomy, and an abnormal diaphragm.[2-4]
The scimitar sign is an important diagnostic finding for this disease, but by itself it is not necessarily a specific one. Sanger et al, Mohiuddin et al, Pearl, and Tumbarello et al reported cases in which a scimitar vein returned to both the IVC and the LA, as in our patient 1. The operation performed for this type of defect has been reported in three cases in the medical literature. Gazzaniga et al reported a case without atrial septal defect. The right atrium was opened under cardiopulmonary bypass to attempt intracardiac repair, but an intact interatrial septum was found and the operation was completed by ligation of the anomalous vein. Endo et al reported that the heart was rotated under cardiopulmonary bypass to confirm this communication, and the operation was completed with simple ligation. Thus, in two of these cases, atrial septal defect was absent, and simple ligation was sufficient. Unnecessary intracardiac examination under cardiopulmonary bypass was performed because of the incomplete preoperative diagnosis. In patient 1, retrograde angiography of the anomalous vein with balloon occlusion confirmed that there was satisfactory communication between the anomalous vein and the LA. Thus, an exact preoperative diagnosis was obtained. An exact preoperative diagnosis was required to choose an operative procedure because simple ligation is possible in some cases with an intact interatrial septum.
In contrast, Morgan and Forker, and Goodman et al reported cases presenting the scimitar sign with a normal return to the LA. In these cases, there is no need for surgery. However, only three such cases including our case have been reported. These variants may provide some insight into the embriogenesis of the scimitar vein and partial anomalous pulmonary venous drainage.
In normal development, the primitive connection between the pulmonary vascular bed and systemic veins disappears after connection is established between the LA and the pulmonary vein. However, the embryonic connection between the pulmonary and systemic vascular beds may persist if the communication with the LA is obstructed, resulting in partial anomalous pulmonary venous drainage. In patient 1, the embryonal connection seemed to have developed without degeneration, even after a normal pulmonary venous communication was formed. Otherwise, in patient 2, the delay in the development of the common pulmonary vein might maintain the fetal connection and form the scimitar vein. But it finally resulted in normal return to the LA without connection with the IVC.
However, it is important to make a precise diagnosis for these variant types of this disease in order to plan the best management for the patient.
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