Background
Scimitar syndrome is a rare congenital cardiovascular anomaly characterised by anomalous pulmonary venous drainage of the right lung to the inferior vena cava. This is alongside variable hypoplasia of the right lung, mesocardia, hypoplasia, or other malformation of the right pulmonary artery and major aorto-pulmonary collaterals. Reference Anderson, Baker, Macartney, Rigby, Shinebourne and Tynan1
Scimitar syndrome has bimodal presentation, either in infancy or in paediatric/adult form with an incidence 1–3 in 100,000 births with a 2:1 female predominance. Reference Dupuis, Charaf, Brevière, Abou, Rémy-Jardin and Helmius2 The infantile form is rarely an isolated abnormality and has up to 75%, of associated lesions. It typically presents with failure to thrive, heart failure, and pulmonary hypertension. In contrast, the paediatric/adult form is less severe and may be asymptomatic at diagnosis. Reference Gudjonsson and Brown3,Reference Vida, Guariento, Milanesi, Gregori and Stellin4
We present a case of a male infant diagnosed postnatally with Scimitar syndrome with relatively well-formed right pulmonary artery, managed with an unconventional surgical approach.
Case presentation
The infant was born at 39 weeks weighing 2.89 kg, with an antenatal diagnosis of ventriuclar septal defect, pulmonary stenosis, and difficulty in visualising the right pulmonary veins. He was discharged after an uncomplicated postnatal course.
At 10 days, he presented with bronchiolitic symptoms. The brain natriuretic peptide, performed due to his antenatal findings, was >35,000 pg/ml. He was commenced on oral diuretics at discharge.
At 4 weeks, he was re-admitted with worsening heart failure. An echocardiogram showed a large ventriuclar septal defect, moderate pulmonary stenosis with Vmax of 3.3 m/sec. His chest X-ray showed mesocardia, a small right lung, and interstitial shadowing. His diuretics were optimised, and Captopril was added.
At 4 months, paediatric cardiology review revealed oxygen saturations of 93% in room air and increased work of breathing. An echocardiogram showed an additional vessel draining into the inferior vena cava at the inferior vena cava–right atrial junction, a moderate sized inter-atrial communication with left-to-right flow, a moderate inlet ventriuclar septal defect with left-to-right flow with an additional muscular ventriuclar septal defect, and valvar pulmonary stenosis with Vmax of 4.3 m/sec. CT imaging, Figure 1, showed partial anomalous pulmonary venous drainage, Scimitar variant, of the entire right lung to inferior vena cava, with mild junctional narrowing, and a well-developed right pulmonary artery in addition to the echocardiographic diagnosis.
CT thorax imaging: ( a ) demonstrating right pulmonary veins draining into dilated inferior vena cava, ( b ) demonstrating a well-developed right pulmonary artery.
Subsequently, he underwent cardiac catheterisation for haemodynamic assessment and transluminal closure of systemic-to-pulmonary collateral arteries (Figure 2). The oxygen saturations under general anaesthetic were Superior Vena Cava (SVC) 30%, inferior vena cava 76%, Right Atrium (RA) 94%, Right Ventricle (RV) 85%, and pulmonary artery 85%. The mean pulmonary artery pressure was 24 mmHg, with evidence of high Qp.
Cardiac catheterisation imaging: ( a ) demonstrating the Scimitar vein, ( b ) demonstrating aorto-pulmonary collaterals supplying the right lung.
A few weeks later he was admitted with worsening high Qp failure. He required invasive ventilation, inotropic support, and intensive diuresis.
A cardiac MRI, performed to further assess haemodynamics, showed a Qp:Qs of 2.6:1 with bidirectional shunting across the inlet ventriuclar septal defect. The majority of the high Qp originated from the anomalous pulmonary venous drainage of the right lung. In addition, MRI confirmed a smaller right lung and a dysplastic, severely stenosed pulmonary valve. Given the large Scimitar shunt, banding of the right pulmonary artery was proposed, pending later closure of the inlet ventriuclar septal defect along with baffling the right pulmonary veins to the left atrium.
At 5 months of age, he underwent right pulmonary artery banding. He was discharged home 2 weeks after the successful procedure with right pulmonary artery band velocity of 4.1 m/s and saturation of 90% in room air.
At follow-up, he remained clinically well, with only mild breathlessness, saturations above 90% in room air without hepatomegaly. He was fully bottle fed and gaining weight. Subsequent echocardiogram showed preserved systolic function, and a tight right pulmonary artery band with restricted flow (Vmax 3.09 m/s) across it.
Discussion
Severe symptoms of Scimitar syndrome presenting in infancy are usually due to shunt-induced congestive heart failure and/or pulmonary hypertension, requiring a multidisciplinary management approach, primarily with diuresis, to relieve heart failure prior to surgical repair. Reference Chowdhury, Anderson and Sankhyan5,Reference Corvol, Hascoet, Le Bret and Nathan6 Therefore, comprehensive segmental echocardiographic assessment is vital for early diagnosis to enable timely optimisation of treatment. In symptomatic infants, catheter collateral vessel embolisation is performed to improve pulmonary hypertension and heart failure. Reference Corvol, Hascoet, Le Bret and Nathan6,Reference Korkmaz, Yildiz, Onan, Cetin and Babaoglu7,Reference Brunet-Garcia, Zuccarino, Martínez and Carretero Bellon8 Surgical options depend on the configuration and drainage site of the Scimitar vein and associated cardiac lesions. The optimum surgical repair involves redirection of the Scimitar vein to the left atrium; however, re-intervention is required in up to 30% of cases due to stenosis or occlusion of the Scimitar vein. Reference Chowdhury, Anderson and Sankhyan5 Hence, preference is to delay surgical repair until the patient is larger, typically over 10 kg. As described by Vida et al, surgical outcomes were related to the age of the patients and those requiring surgical repair under 1 year of age had relatively high post-operative mortality and complication rates compared to older patients. Reference Vida, Guariento, Milanesi, Gregori and Stellin4
Pulmonary artery banding is a widely used surgical approach to control pulmonary blood flow to manage heart failure in children with post-tricuspid shunts. In this case, it was initially felt that the native pulmonary stenosis would provide a balanced circulation. However, the patient presented with high pulmonary blood flow. Therefore, a right pulmonary artery band was performed. Notably, neither Vida et al. (2010) Reference Vida, Guariento, Milanesi, Gregori and Stellin4 nor Dusenbury et al. (2013) Reference Dusenbury, Geva and Seale9 studying cohorts of patients with Scimitar syndrome described pulmonary artery banding as a treatment strategy.
The right pulmonary artery band was indicated due to an unusually well-developed right lung and right pulmonary artery which allowed high right lung blood flow, the pulmonary venous effluent, which exclusively drained to the right atrium. The procedure reduced right lung blood flow and the shunt via the Scimitar vein to control heart failure in the index case. This unconventional approach was guided by precise haemodynamic assessment using cardiac MRI, echocardiography, and cardiac catheter data, alongside clinical interpretation.
The successful outcome in this case suggests that more patients with Scimitar syndrome with well-developed right pulmonary artery presenting with high Qp heart failure could benefit from this approach. However, we acknowledge this anatomical and physiological presentation is unusual.
