Gadolinium-Enhanced Magnetic Resonance Angiography in Scimitar Syndrome: Diagnosis and Postoperative Evaluation

Abstract

We report the 1st magnetic resonance demonstration of both an anomalous pulmonary venous drainage and systemic arterial supply in a patient with scimitar syndrome. With its superior imaging capabilities, gadolinium-enhanced magnetic resonance angiography provides a powerful diagnostic tool for this complex congenital lesion and offers the possibility of surgical repair and follow-up without conventional cardiac catheterization.

We report our use of gadolinium-enhanced magnetic resonance angiography to demonstrate the anomalous pulmonary venous drainage and the systemic arterial supply in a patient with scimitar syndrome. With its superior imaging capabilities, gadolinium-enhanced magnetic resonance angiography provides a powerful diagnostic tool for this complex congenital lesion and offers the possibility of surgical repair and follow-up without conventional cardiac catheterization.

Case Report

In June 1998, a 40-year-old man presented to an outside hospital with shortness of breath and a syncopal episode. His medical history was remarkable only for an episode of renal infarction 5 years earlier. A computed tomographic (CT) scan of the chest was performed to evaluate for possible pulmonary embolus. This revealed a vascular mass in the lower lobe of the right lung, suspected to be an arteriovenous malformation. Further examination of the outside CT scan of the chest showed the mass to be an abnormal pulmonary vein draining into the infradiaphragmatic inferior vena cava (IVC). Review of parenchymal windows (not shown) showed a small, unilobar right lung, a small pulmonary artery, a hyparterial bronchus, and an anomalous bronchial branching pattern. There was no evidence of parenchymal consolidation to suggest sequestration. The constellation of findings was consistent with scimitar syndrome. Right heart catheterization showed a marked increase in the oxygen saturation from the infradiaphragmatic IVC to the right atrium, consistent with a 2:1 left-to-right shunt.

After an initial 1-cc timing bolus of gadolinium was administered to optimize visualization of the scimitar vein, gadolinium-enhanced magnetic resonance angiography (MRA) was performed. The MRA clearly delineated the presence of the scimitar vein, which was seen to be draining a significant portion of the right lung. In addition, 2 aberrant vessels from the abdominal aorta were found to be supplying the right basilar segments and the right hemidiaphragm (Fig. 1). The right kidney was atrophic, which was consistent with the previous history of renal infarction. Conventional thoracic angiography was performed to view the aberrant arterial supply. This confirmed the presence of the anomalous draining vein and the systemic arterial supply to the basilar segments of the right lung (Figs. 2, 3).

Fig. 1 Gadolinium-enhanced magnetic resonance angiography shows a large scimitar vein that drains most of the right lung into the intrahepatic inferior vena cava (solid arrows). Note the 2 abdominal aortic branches, which supply the right lower lobe and diaphragm (open arrows).

Fig. 2 Delayed image from a pulmonary arteriogram confirms the presence of the scimitar vein draining into the intrahepatic inferior vena cava (long arrow). Note early filling of the right atrium (short arrow).

Fig. 3 Abdominal aortography confirms the presence of a systemic artery that supplies the right basilar segments (arrows).

At surgery, we performed a right atriotomy. We were unable to locate the scimitar vein by intrapericardial dissection. Dissection of the right pleural space disclosed an 18-mm pulmonary vein and a 5-mm systemic artery. The anomalous systemic arterial supply was doubly ligated and subsequently divided. The anomalous vein was transected and brought behind the phrenic nerve into the pericardium. In the left atrium, a 2-cm opening was made and the pulmonary vein was anastamosed end-to-end to the atrium, using running sutures of 4–0 polypropylene. This created an anastomosis that admitted a 14-mm probe with ease. The interatrial septum and the free atrial wall were closed, and after deairing was performed, the patient was weaned from cardiopulmonary bypass without difficulty. The patient made an uneventful recovery and showed improvement in oxygenation and subjective improvement in exercise tolerance.

Postoperative MRA evaluation was performed using imaging parameters similar to those used for preoperative evaluation. This confirmed the patency of the anastomosis of the scimitar vein to the left atrium and the ligation of the supradiaphragmatic component of the systemic artery to the right lower lobe (Fig. 4).

Fig. 4 Postoperative gadolinium-enhanced magnetic resonance angiography shows the redirected scimitar vein draining into the left atrium (solid arrows). Note ligation of the systemic arterial supply (open arrows).

Discussion

The 1st description of scimitar syndrome ¹ did not mention the presence of a systemic arterial supply. The incidence of systemic arterial supply varies, and it is crucial that this be identified in patients for whom surgery is contemplated. Traditionally, evaluation of systemic arteries has been performed with conventional aortography, but computed tomographic (CT) scanning has also demonstrated these aberrant vessels. ² Gadolinium-enhanced MRA has been used previously to evaluate scimitar syndrome. ³ To the best of our knowledge, however, ours is the 1st MRA demonstration of both an anomalous pulmonary venous drainage and a systemic arterial supply in a patient with scimitar syndrome. The close similarity of the conventional angiogram and the gadolinium-enhanced MRA suggests that MRA can be used noninvasively to provide comprehensive evaluation of the vascular anatomy in this syndrome.

Surgical management of scimitar syndrome is determined by the patient's symptoms. The clinical presentation of these patients can vary widely, and the age at which this syndrome becomes manifest can range from infancy to adulthood. ⁴ Infants who present with scimitar syndrome are almost always very ill, with evidence of congestive heart failure and severe pulmonary hypertension. Their symptoms are secondary to the associated congenital cardiac lesions, the presence of systemic collateral arterial supply, and the obligatory left-to-right shunt from the anomalous pulmonary venous drainage. Recently, Huddleston and colleagues ⁵ provided an excellent summary of the surgical strategy for repair in infants.

Adults, on the other hand, generally present with minor symptoms, or none at all, and surgical intervention is usually unnecessary. In patients who have associated tracheobronchial anomalies (such as bronchiectasis or pulmonary sequestration), resection of the affected lung may be indicated. Surgical intervention may also be required for patients who have associated cardiac anomalies or left-to-right shunts greater than 2:1. In these cases, identification of a systemic arterial supply is important in order to avoid inadvertent transection during surgery.