Introduction
Scimitar syndrome is a rare congenital heart anomaly characterised by partial anomalous pulmonary venous drainage, most commonly into the inferior vena cava, with an incidence of 1–2 per 100,000 births.1 Single ventricle defects, including double-inlet left ventricle, hypoplastic left heart syndrome, and tricuspid atresia, occur in 4–8 per 10,000 births.Reference Rao2,Reference O’Leary, Hoffman and Allan3 Infants with single ventricle anatomy are traditionally managed by staged total cavo-pulmonary connection (Fontan), though inter-stage mortality remains high at 5–15%.Reference O’Leary, Hoffman and Allan3 The rare combination of single ventricle anatomy and Scimitar syndrome has been scarcely reported.Reference Co-Vu, Kirkpatrick and Samyn4,Reference McBride, Huddleston and Balzer5,Reference Aron-Said, Opel and Alkon6
We previously reported the largest cohort of single ventricle Scimitar syndrome patients and found that those with severe right lung and pulmonary artery hypoplasia (z score < −2) had significantly worse outcomes with staged palliation.Reference Eckhauser, O’Byrne, Weinberg, Ravishankar, Spray and Gaynor7 This study presents outcomes of patients who underwent primary transplantation or were bridged to transplant.
Materials and methods
This case series included single ventricle patients with Scimitar syndrome treated at the Children’s Hospital of Philadelphia from 2011 to 2022. Patients received a transplant or treatment to optimise them for future transplant. Pulmonary artery z-scores were obtained by echocardiography. Case reports do not meet the definition of research under our institutional protocol and do not require Institutional Review Board approval.
Case series
Patient 1
A term female with hypoplastic left heart syndrome and Scimitar syndrome had severe bilateral pulmonary artery hypoplasia (z score −3 for both) and hypoplastic right lung (Supplementary Figure 1A). Genetic testing, including newborn testing and amniocentesis karyotype and microarray, was negative. She had no pulmonary vein obstruction but had pulmonary hypertension on catheterisation (6 Wood units). She presented cyanotic (oxygen saturation 75%) and in extremis and underwent hybrid stage one palliation consisting of bilateral pulmonary artery banding and placement of a 9 mm x 20 mm Protégé Guidance Positioning System stent at six days of life as a bridge to cardiac transplantation. Despite a technically successful operation, the patient experienced cardiogenic shock and reverse coarctation physiology, causing preferential perfusion of the post-stented ductal region instead of the hypoplastic arch supplying the brain and upper extremities. The ensuing multisystem organ failure resulted in her death at three months of age.
Patient 2
A term female with transposition of the great arteries, double-inlet left ventricle, and Scimitar syndrome (Figures 1, 2, Supplementary Figure 1B) had severe bilateral pulmonary artery hypoplasia (right z score –3.54, left z score –3.04). She had no known genetic mutations on newborn testing of single nucleotide polymorphism microarray, but had severe left bronchus hypoplasia and moderate right pulmonary vein obstruction. After failed medical management of left pulmonary hypertension (7 Wood units), she underwent right pulmonary artery reimplantation and left pulmonary artery banding at age three for lung recruitment and bridge to transplantation. Her right pulmonary artery was reimplanted anterior to the bronchus to alleviate compression and increase flow. She remains well 18 months postoperatively.
Off-axis coronal view demonstrates severe main pulmonary artery dilation. There is a left SVC to coronary sinus. The scimitar vein is observed connecting to the IVC just above the diaphragm. There is moderate discrete stenosis (*) of the scimitar vein at its connection to the IVC. CoS = Coronary Sinus; IVC = Inferior Vena Cava; LA = Left Atrium; LSVC = Left Superior Vena Cava; MPA = Main Pulmonary Artery; RA = Right Atrium; RHV = Right Hepatic Vein.
Figure 1 Long description
The image displays an off-axis coronal view of a heart with severe dilation of the main pulmonary artery. A left superior vena cava is present, draining into the coronary sinus. The scimitar vein is visible, connecting to the inferior vena cava just above the diaphragm. There is moderate discrete stenosis at the connection point of the scimitar vein to the inferior vena cava. The labeled structures include the coronary sinus, inferior vena cava, left atrium, left superior vena cava, main pulmonary artery, right atrium, and right hepatic vein.
Off axis coronal view demonstrates moderate left pulmonary artery hypoplasia without proximal stenosis. The left pulmonary veins connect normally to the left atrium. IVC = Inferior Vena Cava; RA = Right Atrium; RHV = Right Hepatic Vein.
Figure 2 Long description
The image presents a cross-sectional view of the heart and its associated veins. The right atrium (RA) and right hepatic vein (RHV) are clearly labeled. The inferior vena cava (IVC) is also visible, along with the Scimitar vein, which connects to the left atrium. The image highlights the moderate left pulmonary artery hypoplasia without proximal stenosis, indicating a rare congenital heart anomaly known as Scimitar syndrome.
Patient 3
A term male with hypoplastic left heart syndrome, double outlet right ventricle, and Scimitar syndrome had right pulmonary artery hypoplasia (z score –3.08), but normal sized left pulmonary artery size (z score 0.7) (Supplementary Figure 1C). Genetic testing, including newborn screening and single nucleotide polymorphism microarray, was negative. Initial Norwood procedure was performed at six days old. Scimitar vein stenting and aorto-pulmonary collateral embolisation were performed at six months to decrease pulmonary resistance and optimise for future palliation or transplant. At age 14 months, he developed profound cyanosis (oxygen saturation 68%) and underwent redo Blalock–Taussig–Thomas shunt placement before being listed for heart transplant. He underwent transplantation but developed acute rejection resistant to immunosuppression, requiring extracorporeal membrane oxygenation support. Three weeks post-transplant, he developed endocarditis and multiorgan failure, dying six weeks post-transplant.
Discussion
The combination of Scimitar syndrome and single ventricle physiology presents significant challenges. Because of its rarity and variable severity of right lung hypoplasia and pulmonary hypertension, there is no consensus on optimal management or treatment recommendations offered in the current literature. Our prior cohortReference Eckhauser, O’Byrne, Weinberg, Ravishankar, Spray and Gaynor7 concluded that severe hypoplasia (z score < –2) often precludes successful staged palliation, suggesting early transplantation may be preferable. All patients in the current series had right pulmonary artery z-scores ≤ –3. Here, two were listed for transplant: one expired before a donor was available, and the other expired after transplant due to complications. The third patient (Patient 2) underwent a palliative procedure to improve transplant candidacy and remains stable.
These cases highlight the persistent knowledge gaps that exist in determining optimal treatment strategies for this rare and complex population. Despite shifting towards transplantation following prior reports, the outcomes remain grim. Further research is urgently needed to establish best practices for managing patients with combined Scimitar syndrome and single ventricle physiology.
Supplementary material
The supplementary material for this article can be found at https://doi.org/10.1017/S1047951125111025.
Acknowledgements
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