Scimitar syndrome: incidence, treatment, and prognosis
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- Wang, CC., Wu, ET., Chen, SJ. et al. Eur J Pediatr (2008) 167: 155. doi:10.1007/s00431-007-0441-z
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This study is based on a database of 16 years; we sought to define the incidence and outcome of scimitar syndrome. Of 8,771 patients, 5 (0.057%) with scimitar syndrome were identified and constituted the study population. Follow-up ranged from 1 to 16 years (median: 10 years). Diagnosis was assured by computed tomography in four patients and by cardiac catheterization in one. Two patients presented with respiratory distress soon after birth and required early pneumonectomy in one case and coil embolization of the abnormal feeding arteries to the right lower lung followed by surgical rerouting of the abnormal pulmonary vein and repair of the atrial septal defect in the other case. The former was supported by ventilator therapy for 3 years after pneumonectomy, but was finally weaned from the ventilator. Among the other three, two had repeated pneumonia that resolved after rerouting of the abnormal right pulmonary vein and cardiac repair. The asymptomatic child did not receive any intervention. In spite of the abnormal orientation of the airways, none of the four patients with detailed computed tomography imaging showed any significant compression of the airways. All five patients were doing well as of the last follow-up. In conclusion, scimitar syndrome is a very rare disease in this Asian country and the varied symptoms, such as tachypnea and repeated infection, could be improved after interventions.
KeywordsScimitar syndrome Congenital heart disease Airway anomaly Pulmonary veins
Scimitar syndrome is a rare congenital disease that is characterized by dextroposition, hypoplasia of the right pulmonary artery, underdevelopment of the right lung, abnormal connection of the right pulmonary veins to the inferior vena cava-right atrial junction (giving the scimitar appearance on the frontal chest radiography), and anomalous systemic arterial supply to the right lower lung, often to its basal segments . The clinical presentations are quite diverse, ranging from severe congestive heart failure in infancy to mild symptoms in childhood [4, 5]. The physiological determinants include the extent of the right-sided volume overload, amount of systemic to venous shunting, and complex interaction between the deviated airway and great vessels. While some patients present with dyspnea, respiratory distress, cyanosis, or cardiac failure, some present with recurrent pneumonia, and others can present palpitations with near-syncope. Symptoms can start during infancy (infantile form) or beyond (childhood/adult form) [2, 4, 5, 13]. The infantile form is sometimes associated with pulmonary hypertension, cardiac failure, and a worse prognosis. The advances in cardiovascular imaging demonstrate greater details of the spatial relationship and thereby provide the information for tailored treatment and improving prognoses . The usefulness of magnetic resonance angiography for diagnosis of scimitar syndrome in early infancy has been reported . We retrospectively studied patients with scimitar syndrome and defined the incidence, clinical presentation, and outcome of this rare disease in a tertiary referral center in an Asian country.
Patients and methods
Patients with a diagnosis of scimitar syndrome were identified from the congenital heart disease database from January 1989 to December 2005. This database included all the cardiac patients aged younger than 15 years and registered with a cardiac diagnosis of congenital heart disease in our pediatric cardiology program after an integrated echocardiography evaluation. Their medical records, including age at presentation, symptoms, associated anomalies, cardiac catheterization, and computed tomography data, surgical treatments, and outcomes were analyzed. Follow-up data were obtained for all patients.
Descriptive statistics were applied and nominal variables are presented as means or medians, with ranges as indicated.
Clinical characteristics of five patients with scimitar syndrome
Associated cardiac anomaly
Associated lung anomaly
Tachypnea, respiratory failure
Collateral artery from DsAo to right lower lung
Coil embolization of feeding artery, the repair of ASD and PAPVR
Uneventful, F/U 1 year
Tachypnea, respiratory failure
Collateral artery from DsAo to right lung
Right pneumonectomy, tracheostomy with home ventilator 3 years
Uneventful after weaning from ventilator, F/U 16 years
Tachypnea, repeated pneumonia
Rerouting of PAPVR, repair of ASD
Uneventful, F/U 14 years
Tachypnea, repeated pneumonia, heart murmurs
Horseshoe lung, bilateral bifurcated tracheobronchial tree
Rerouting of PAPVR, repair of ASD
Uneventful, F/U 2 years
Bilateral bifurcated tracheobronchial tree
Uneventful, F/U 6 years
Associated cardiovascular and other pulmonary anomalies
Treatment and outcome
Cardiac catheterization in all five patients revealed a mean pulmonary arterial pressure that ranged from 18 to 40 mmHg (mean: 26.8) while the Qp/Qs (pulmonary/systemic flow ratio) ranged from 1.9 to 2.9 (mean: 2.4). Significant left-to-right shunt and mild pulmonary arterial hypertension were noted in the two patients with infantile scimitar syndrome (patients 1 and 2). Patient 1 had severe respiratory distress and required ventilator support soon after birth. After stabilization, she was still dependent on nasal continuous positive airway pressure (CPAP) support. Coil embolization of the feeding artery to the lower right lung was successfully performed at the age of 10 days. She was then weaned from the ventilator. At the age of 6 months, because of failure to thrive, she underwent surgical rerouting of the abnormal pulmonary vein and repair of the ASD. She was doing well at the next follow-up visit. Patient 2 had extensive shunting from the abnormal feeding artery of the infradiaphragmatic descending aorta to the right lower lung. She developed respiratory distress soon after birth and was intubated. She underwent right pneumonectomy at 4 months of age due to persistent respiratory instability. However, after the operation, she could not be weaned from the ventilator, due to postpneumonectomy syndrome. After chronic ventilator support for 3 years, she was finally weaned off the ventilator and has led an uneventful life since then. Patients 3 and 4 underwent rerouting of their anomalous right pulmonary veins and repair of their ASDs. Both had satisfactory hemodynamics and the symptoms of tachypnea and repeated infections resolved. Patient 5 did not receive any interventions and has been doing well. The ASD closed spontaneously at the age of 11 years.
We found that (1) scimitar syndrome was a very rare disease with an incidence of 0.057% among the population presenting with congenital heart disease; (2) symptoms of tachypnea and even repeated infection were improved after rerouting of the abnormal pulmonary veins and repair of the associated cardiac defects; and (3) in spite of the abnormal airway positions, the chance of compression of the airway was low.
Scimitar syndrome was first described in 1836 when it received its name [12, 18]. Its prevalence is very low and is estimated at 1–3 of every 100,000 live births . A female predominance was also found in our study . Among congenital cardiac defects, the incidence of scimitar syndrome, as shown in this study, is extremely low and is much lower than that of the three other forms of rare congenital heart disease, i.e., persistent truncus arteriosus (0.47%) , aortopulmonary window (0.15%), and right atrial isomerism (1.63%) . The diagnosis is usually made based on the characteristic chest X-ray films and can be confirmed by angiography, but is now done mostly by noninvasive computed tomography or magnetic resonance angiography. Among our patients, the diagnosis was confirmed in the four patients who underwent computed tomography. Contemporary data of the great vessels, cardiac chambers, and airways are useful for surgical planning. In two-thirds of cases, the scimitar vein provides drainage for the entire right lung, but in one-third, this vein drains only the lower portion of the right lung, just as in our patient 4 . Obstruction of this abnormal pulmonary venous flow is common and may contribute to ipsilateral lung and pulmonary artery hypoplasia [2, 7, 16].
Abnormalities of lung lobulation and bronchial branching are common in this syndrome . The horseshoe or crossover lung anomaly may occur, as in patient 4, and is another common malformation associated with scimitar syndrome [6, 8, 9, 21]. Airway anomalies, although common, do not seem to be major factors for symptoms. Furthermore, many cases have associated pulmonary sequestration or anomalous systemic arterial supply to a part of the right lung, without true sequestration from the bronchial connection . The extent of pulmonary sequestration and the existence of a large systemic artery is a major pathophysiological determinant [17, 19]. In our study, the two patients with infantile scimitar syndrome had significant left-to-right shunting from the abnormal systemic collateral arteries to the right lower lung. Pulmonary sequestration may also lead to early onset of symptoms, such as repeated infection. Although none of our patients had pulmonary sequestration, repeated pulmonary infection was the major symptom of two patients and was improved after rerouting of the abnormal pulmonary vein. This was attributed to the relief of pulmonary venous stenosis of the abnormal returning vein; thereby the localized pulmonary congestion was ameliorated.
Atrial septal defect of the secundum type is the most commonly associated cardiac anomaly and was present in all of our patients. According to the literature, the spectrum of other associated cardiac anomalies is wide [15, 19].
The asymptomatic patients with small left-to-right shunting and normal pulmonary artery pressures can be followed conservatively. For those with infantile scimitar syndrome, the presence of pulmonary hypertension or failure of response to medical therapy warrants prompt intervention. Patients with primary respiratory symptoms who have sequestrated right lower lobes may benefit from lobectomy and interruption of the abnormal systemic arteries by coil embolization or surgical ligation [1, 13]. For patients with congestive heart failure, repeated pneumonia, or pulmonary-to-systemic blood flow ratios greater than 1.5 and pulmonary hypertension, it is important to reroute the anomalous right pulmonary veins and repair the associated cardiac defects, such as an ASD . Previous studies reported variable results of treatment of scimitar syndrome, with mortality ranging from 64 to 16% [4, 5, 13, 19]. Anomalous systemic arterial supply, severely obstructed pulmonary venous connections, and complex congenital heart malformations all contribute to the poor prognoses . Sometimes right lobectomy or pneumonectomy is preferred because right pulmonary veins remain obstructed after the procedure [19, 23]. After pneumonectomy, the heart deviates more to the right thorax and the aorta transverses from the right hemithorax to the left hemithorax, which may cause compression of the trachea, the so-called right pneumonectomy syndrome . Indeed, three patients in our study received surgical pulmonary venous rerouting (with prior coil deployment for the abnormal systemic arterial collateral in one) and ASD repair with satisfactory results. One had to undergo pneumonectomy and required ventilator support for 3 years due to the right pneumonectomy syndrome.
In conclusion, scimitar syndrome is a very rare disorder and with varied symptoms. The diagnosis can usually be made by chest radiography in conjunction with computed tomography. Airway variation is common, but is usually not a major concern. Tailored transcatheter coil deployment into the abnormal collateral arteries and surgical rerouting of the pulmonary veins can be performed in patients with scimitar syndrome with low interventional risks.