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Ann Thorac Surg 1999;67:154-159
© 1999 The Society of Thoracic Surgeons

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Original Articles

Scimitar syndrome presenting in infancy

^a Departments of Surgery and Pediatrics, Washington University School of Medicine, St. Louis Children’s Hospital, St. Louis, Missouri, USA

Address reprint requests to Dr Huddleston, Children’s Hospital, #1 Children’s Place, Suite 5W 24, St. Louis, MO 63110

Presented at the Thirty-fourth Annual Meeting of The Society of Thoracic Surgeons, New Orleans, LA, Jan 26–28, 1998.

	Abstract

Top Abstract Introduction Patients and methods Results Comment References

 
Background. Scimitar syndrome has a variable presentation based on the age at which the diagnosis is made. In general, infants presenting in heart failure have a greater number of associated anomalies and their prognosis is much worse.

Methods. We reviewed the records of all patients under our care at St. Louis Children’s Hospital who presented with symptoms attributable to scimitar syndrome during their infancy. Twelve patients were identified. The average age at presentation was 6 weeks.

Results. The most common symptom at presentation was tachypnea. The chest roentgenogram demonstrated dextroposition of the heart and hypoplastic right lung. Only 1 patient had the classic "scimitar sign." Cardiac catheterization demonstrated pulmonary hypertension (pulmonary artery systolic pressure, 73.9 ± 21.8 mm Hg). The Qp:Qs was 3.1 ± 1.5:1. Two patients with severe associated anomalies were treated medically and both died. Two patients underwent occlusion of the systemic collaterals; one died and the other ultimately underwent complete repair due to persistence of the symptoms of heart failure. Two patients had primary right pneumonectomy and both are alive and well. Seven patients underwent complete repair (one after coil occlusion of the systemic arterial collaterals) and one died; three subsequently developed occlusion of the baffle from the orifice of the anomalous pulmonary vein and required pneumonectomy. Two patients required lung transplantation due to persistent pulmonary hypertension in one and recurrent bilateral pulmonary venous stenosis in the other.

Conclusions. Infants presenting with scimitar syndrome generally have symptoms of tachypnea and chest roentgenograms showing dextrocardia and hypoplastic right lung. Although repair of the anomalous venous return and ligation of collaterals is generally recommended, right pneumonectomy (either as primary therapy or if repair failed) had similar early and late results.

	Introduction

Top Abstract Introduction Patients and methods Results Comment References

 
Scimitar syndrome is a rare congenital anomaly consisting of partial anomalous pulmonary venous return from the right lung to the inferior vena cava (IVC), hypoplasia of the right lung with dextroposition of the heart, and anomalous systemic arterial supply from the abdominal aorta to a portion of the right lung (usually lower lobe). Not all patients with scimitar syndrome will have all the above-mentioned findings, but the sine qua non is the anomalous pulmonary venous return of all or most of the right lung to the IVC (Fig 1) creating the image of a Turkish sword on chest roentgenogram. The variability and pathologic spectrum of this disorder has been well described by other investigators [1–3]. Other cardiac anomalies may also coexist. The clinical presentation of these patients is quite variable—from asymptomatic to significant heart failure—and because of that, the age at presentation can differ significantly, from infancy to adulthood [4]. When patients with scimitar syndrome present during infancy the symptoms are usually severe and the associated anomalies complex [5]. We reviewed our experience with those patients who present during the first 6 months of life to characterize more accurately their clinical course and outcome.

View larger version (141K): [in this window] [in a new window]   Fig 1. Frame taken from the cardiac catheterization of one of the patients. The catheter travels up the inferior vena cava into the anomalous pulmonary vein. The dye demonstrates the vein entering the inferior vena cava at a level below the diaphragm. Although it is difficult to determine, the vein overlies the right heart border so that it could not be seen distinct from the cardiac silhouette. There was no "scimitar sign" on the plain chest x-ray.

	Patients and methods

Top Abstract Introduction Patients and methods Results Comment References

The patients and their characteristics are depicted in Table 1. The mean age at presentation of this group was approximately 6 weeks (46 ± 36 days) and ranged from 2 days to 4 months of age. There were 4 girls and 8 boys. The entire pulmonary venous drainage from the right lung entered the IVC in 8 patients and in the other 4 there was some pulmonary venous return (from all or part of the right upper lobe) to the left atrium with the remainder entering the IVC. The anomalous pulmonary venous return entered the IVC below the level of the diaphragm in all infants.

Technique of repair
Repair of the partial anomalous pulmonary venous return was accomplished by one of two methods—either baffling the anomalous vein from its point of entry into the IVC through the right atrium to the left atrium (LA) by way of an atrial septal defect (n = 2) [7] or by dividing it off the IVC, reimplanting it in the back wall of the LA or in the posterolateral wall of the right atrium and baffling from that point to the LA via an atrial septal defect (n = 5) [8]. The decision regarding type of repair was made on the basis of the location of the anomalous "scimitar vein." If it was running anterior to the hilum or on the anterior surface of the right lung, it was divided and reimplanted into the posterolateral wall of the right atrium. If it was located within or running along the posterior surface of the lung, repair was performed using a long baffle from the entry into the IVC all the way up to the atrial septum; the concern was that if located in a posterior position, it would likely kink when mobilized to come anteriorly to the right atrium. In either case, profound hypothermia with a period of circulatory arrest was used; in all patients, the anomalous pulmonary vein entered so low in the IVC that direct caval cannulation and access to the anomalous vein was not feasible in these small infants.

When the reimplantation technique was used (Fig 2) [8], the anomalous pulmonary vein was excised with some of the wall of the IVC, carefully avoiding injury to the hepatic veins lying nearby. The wall of the pulmonary vein is generally quite thin; using some of the wall of the IVC facilitates the subsequent anastomosis to the right atrium. The resultant defect in the IVC is patched with either pericardium or synthetic material. The pulmonary vein is then mobilized to reach the posterolateral wall of the right atrium opposite the atrial septal defect. It is unusual to be able to reach the left atrium because of the rotation of the heart due to hypoplasia of the right lung. The pulmonary vein is then opened longitudinally to increase the orifice size, as it is frequently stenotic. This is then sewn to a defect created in the right atrial wall. A patch from this point to the atrial septal defect is then sewn to simultaneously close the defect and baffle the pulmonary venous drainage to the left atrium.

View larger version (25K): [in this window] [in a new window]   Fig 2. (A) An artist’s rendition of the anomalous pulmonary venous drainage of the right lung entering the inferior vena cava below the diaphragm, just above the hepatic veins. (B) The pulmonary vein has been divided off the inferior vena cava taking a bit of the wall of the inferior vena cava with it. It is brought up through the diaphragm and opened longitudinally to enlarge the orifice. It is then sewn to an opening in the mid-portion of the posterolateral wall of the right atrium. The defect in the inferior vena cava is patched with either pericardium or synthetic material. Looking into the right atrium through an atriotomy in the anterior wall, the newly created orifice of the anomalous pulmonary vein is baffled to the left atrium through an atrial septal defect using pericardium or synthetic material.

View larger version (52K): [in this window] [in a new window]   Fig 3. The anomalous pulmonary venous drainage is directed from its orifice in the inferior vena cava to the left atrium through the atrial septal defect. A very large patch of pericardium or synthetic material is necessary for this to reach the atrial septal defect. The right atriotomy nearly always needs to extend down into the inferior vena cava and this usually needs to be patched to enlarge it to allow for the space taken up by the baffle inside the inferior vena cava.

	Results

Top Abstract Introduction Patients and methods Results Comment References

 
Presentation
Nearly all these infants presented with tachypnea and other signs of congestive heart failure such as failure to thrive. One patient also had necrotizing enterocolitis. One patient had cyanosis; she had elevated pulmonary vascular resistance and was shunting right to left across the atrial septal defect. The chest roentgenogram in all patients showed dextroposition of the cardiac silhouette and hypoplasia of the right lung (Fig 4); only 1 patient had the scimitar vein noted on plain chest radiograph. Most (11 of 12) of these infants had an associated atrial septal defect. Other significant cardiac anomalies were also present including multiple ventricular septal defects, coarctation of the aorta, patent ductus arteriosus, and pulmonary vein stenosis (Table 1).

View larger version (138K): [in this window] [in a new window]   Fig 4. This is a typical chest roentgenogram on one of the infants in our series. Note how the cardiac silhouette is displaced to the right. This occurs to such a degree that it is unusual to see a "scimitar sign" in these young patients.

Outcome
Medical treatment
Two patients were treated medically only. One of these was born quite prematurely and had relatively severe hyaline membrane disease. The diagnosis was not made until 8 weeks of age and at that time the PA pressures were suprasystemic. The patient died soon thereafter. The other patient had a variant of Shone’s complex with multiple left heart obstructions—mitral and aortic stenosis, coarctation of the aorta. The patient had a patent ductus arteriosus initially, but died soon after that closed.

Surgical treatment
Three procedures were used as primary therapy in our series of infants with scimitar syndrome. These included occlusion of the systemic arterial collateral to the right lung (either with operation or coil occlusion during cardiac catheterization), right pneumonectomy, or complete repair.

Two patients underwent occlusion of the systemic arterial collaterals. One of these was a 3-month-old who presented with cyanosis attributable to pulmonary hypertension and an atrial septal defect along with scimitar syndrome. There was essentially no change in hemodynamics or clinical status after ligation of these collaterals and the patient died 10 weeks later of progressive pulmonary hypertension. The other patient was a 2.4-kg neonate in severe congestive heart failure. Transcatheter coil embolization was undertaken with the intent to improve the heart failure so that the infant might grow and be a better candidate for operation. Heart failure persisted, however, and complete repair was ultimately undertaken during that same hospitalization.

Seven patients underwent complete repair (including the one mentioned above). Two of these were done using the technique of baffling the anomalous pulmonary venous drainage from the entry into the IVC to the left atrium through the atrial septal defect. In both patients the anomalous pulmonary vein was lying posterior to the hilum of the left lung and came out anteriorly at the level of the diaphragm to enter the IVC. Both of these patients developed occlusion of the baffle over the next several months. This was accompanied by hemoptysis and persistent pulmonary hypertension. Both subsequently underwent right pneumonectomy. One has done well, whereas the other infant had persistent pulmonary hypertension and ultimately developed hemodynamic collapse requiring extracorporeal membrane oxygenation for support. Right lung transplant was performed, but the patient died.

The other 5 patients underwent complete repair by reimplantation of the anomalous pulmonary vein. One of those developed occlusion of the baffle and subsequent pneumonectomy but has done well since then and is 14 years postpneumonectomy. One other patient had associated bilateral pulmonary vein stenosis. The repair was accompanied by placement of pulmonary vein stents. The atrial baffle remained patent, but pulmonary venous stenosis recurred and he subsequently has undergone successful bilateral lung transplant; he is currently doing well now 2 years after transplant. The other 3 patients are alive and well with an open, nonstenotic pulmonary venous baffle as demonstrated by follow-up echocardiography (2 patients) or cardiac catheterization (1 patient) at a mean follow-up of 4.9 years. There is no evidence of pulmonary hypertension on the basis of follow-up echocardiograms in these 3 patients successfully treated with reimplantation technique. This was assessed using the Doppler evaluation of the tricuspid valve regurgitant jet to estimate the right ventricular pressure. In all 3 patients the estimated right ventricular pressure was less than 30 mm Hg.

Four patients have survived long term after right pneumonectomy, performed either as a secondary procedure after baffle occlusion or as primary therapy for scimitar syndrome. All are asymptomatic at a median follow-up of 8.8 years. Two have undergone cardiac catheterization with PA systolic pressures of 40 and 35 mm Hg. The 2 other patients have undergone echocardiography and neither has evidence of pulmonary hypertension. All 4 patients are active without respiratory symptoms.

	Comment

Top Abstract Introduction Patients and methods Results Comment References

 
Although patients with scimitar syndrome may have no or minimal symptoms, presentation in infancy is usually due to congestive heart failure from a significant left-to-right shunt. This may be attributable solely to the obligatory shunt from the anomalous pulmonary venous drainage, but is more likely a result of an additional congenital cardiac lesion, such as an atrial or ventricular septal defect [5]. All patients in our series had at least one additional lesion contributing to the left-to-right shunt and all patients had at least moderate pulmonary hypertension noted at the time of cardiac catheterization. The diagnosis should be suspected when an infant presents with tachypnea or other signs of congestive heart failure in association with dextroposition of the heart and hypoplasia of the right lung. On the basis of our experience, the scimitar sign will not likely be seen. This may be related to a greater degree of right lung hypoplasia and dextroposition of the heart than is seen in older patients or perhaps attributable to a prominent thymic shadow. One must maintain suspicion of this diagnosis when there is dextroposition of the heart even if other lesions are present that might be sufficient to explain the clinical situation, such as a ventricular septal defect or coarctation of the aorta.

Pulmonary hypertension is quite common in infants presenting with scimitar syndrome. Two-thirds of the patients in our series had systemic levels of the PA pressure. Several explanations for this exist including a significant intracardiac shunt (eg, ventricular septal defect), stenosis of the anomalous pulmonary vein at its entry into the IVC, stenosis of the other pulmonary veins, the presence of a systemic arterial supply to the right lung or perhaps failure of adaptation of pulmonary arterioles after birth in the presence of excessive pulmonary blood flow [9, 10]. Three of our patients had persistence of the pulmonary hypertension after treatment including one after ligation of the systemic collaterals, one after pneumonectomy for occlusion of the intraatrial baffle, and one due to bilateral pulmonary vein stenosis. All other surviving patients have normalized the PA pressures. When pulmonary hypertension persists after repair, lung transplantation should be pursued as the mortality is very high under these circumstances [5]. This is particularly true when pulmonary vein stenosis accompanies this syndrome.

The role the anomalous systemic arterial collateral plays in this syndrome is unclear. When seen, many have diagnosed the patient as having pulmonary sequestration as an associated finding [5, 11]. One must remember that the anatomic entity of pulmonary sequestration refers to a situation where isolated lung is sequestered from the bronchial tree in addition to having blood supply through an anomalous systemic artery [12]. Careful evaluation of the bronchial distribution at autopsy and with bronchography has not demonstrated pulmonary sequestration in its strictest definition to commonly accompany scimitar syndrome [2, 3]. Although it has been suggested that occlusion of the systemic arterial collateral may play an important role in treatment of both the pulmonary hypertension and heart failure [8, 9, 13, 14], this has been at best an inconsistent experience by us and other researchers [10]. Four of our patients did not have this anomalous systemic artery present and two had no clinical change after either surgical ligation or coil occlusion. Ligation or occlusion of these systemic arteries should be part of the surgical strategy but should be accompanied by repair and correction of associated cardiac defects when present.

The precise nature of the repair to be undertaken in these small infants is unclear. Utilization of a long baffle as reported by Murphy and colleagues [7] had excellent results, but all the patients were adults. Our experience and that of other investigators [11] using this technique in infants has been disappointing. Both of the infants treated in this fashion developed occlusion of the baffle. The factors involved in this include the acute angle that the pulmonary venous blood must take as it courses down to its entry into the IVC and then back up almost 180 degrees to the atrial septal defect. In addition, the pericardium generally used for the baffle may shrink and frequently the orifice of the anomalous pulmonary vein itself is mildly stenotic. Therefore, we prefer the alternative method described by Shumacker and Judd [8] in which the anomalous vein is divided off the IVC and mobilized to reach the right atrial posterolateral wall opposite the site of the atrial septal defect. From there it is a short, straight pathway to the left atrium using a large patch for a baffle. This also affords one the opportunity to enlarge the orifice of the vein by incising longitudinally.

In those patients where the vein travels posterior to the hilum to emerge from under the diaphragmatic surface of the right lung to enter the IVC it would be difficult to mobilize the vein without kinking or twisting it to perform this type of repair. Our recommendation under that circumstance is a right pneumonectomy. Potential long-term risks of a pneumonectomy in an infant include postpneumonectomy syndrome, chronic respiratory insufficiency, and scoliosis. However, in a large series of patients undergoing pneumonectomy during early childhood years, the compensatory growth of the contralateral lung nearly made up for the loss. In fact, there were no obvious untoward effects in these patients followed for more than 30 years [15]. Patients with scimitar syndrome have a right lung that is significantly smaller than a normal right lung to begin with and the left lung has frequently already undergone compensatory growth. Clearly some serious complications may occur late after pneumonectomy, but the majority of children seem to tolerate this well with only mild perturbations in pulmonary function and hemodynamics late after pneumonectomy [16].

A precise description of the course of the anomalous pulmonary vein relative to the hilum of the right lung has not been previously characterized. From our experience there have been two clearly different positions for this vein—one running primarily anterior and the other posterior to the hilum. The posterior location may be suspected from the angiogram of the vein itself (Fig 5). From this, one can note the relatively posterior position of the vein using the esophagus (with the nasogastric tube in place) as a marker. Although mobilization sufficient to reach the more superior aspect of the right atrium might be possible with ligation and division of some segmental veins, the likelihood of kinking the vein still remains high.

View larger version (171K): [in this window] [in a new window]   Fig 5. A straight lateral view of an angiogram of the anomalous right pulmonary vein. The vein in this patient ran a course through the lung that was posterior to the hilum and was not amenable to reimplantation higher into the right atrium. One can note that the vein lies even posterior to the esophagus, which is represented by the radiopaque line on the nasogastric tube marked by the arrow.

In summary, infants presenting with heart failure and dextrocardia with a hypoplastic right lung should be evaluated for the diagnosis of scimitar syndrome. A cardiac catheterization is recommended to confirm the diagnosis, evaluate the pulmonary hemodynamics, identify systemic arterial collaterals and potentially delineate the anatomy of the scimitar vein. The collaterals may be occluded by coil embolization, but that does not replace the need for repair. If possible, the lesion should be repaired using a technique in which the anomalous pulmonary vein is taken off the IVC and anastomosed to the right atrial free wall closer to the atrial septum. The pulmonary venous blood is then baffled to the left atrium across an atrial septal defect. Pneumonectomy is an effective means to correct this anomaly, but should be reserved for symptomatic patients where the anomalous pulmonary vein cannot be transferred up to the right atrial wall.

	References

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