Author: David Fitzgerald, MD and Destiny F. Chau MD - Arkansas Children’s Hospital /University of Arkansas for Medical Sciences - Little Rock, AR
An 18-year-old woman with a history of exertional dyspnea and frequent lower respiratory tract infections undergoes bronchoscopy that demonstrates abnormal right lower lobe bronchial architecture. A chest x-ray demonstrates a nonspecific irregularity over the right lower lung field with dextroposition of the heart, and an echocardiogram reveals right heart dilation. Which of the following congenital heart defects is the MOST likely diagnosis?
EXPLANATION
Scimitar syndrome is a subtype of partial anomalous pulmonary venous return (PAPVR) in which the right pulmonary vein drains abnormally to the inferior vena cava (IVC), typically near the level of the diaphragm. It is associated with varying degrees of right lung hypoplasia and cardiac dextroposition. The name, Scimitar syndrome, is owed to the crescent shape of the anomalous right pulmonary vein resembling the curved blade of a scimitar sword. The incidence is approximately one to three per 100,000 live births, and accounts for 0.5 to 1% of all congenital heart disease.
Scimitar syndrome can present in infancy or early adulthood. In infants, the median age at diagnosis is estimated to be seven months old. Among neonates diagnosed with Scimitar syndrome, up to 75% have associated anomalies, which include right lung hypoplasia, dextrocardia, right pulmonary artery hypoplasia, collateral blood vessels from infra-diaphragmatic aorta to the right lower lobe of the lung, secundum atrial septal defect (ASD), and diaphragmatic hernia. More severe cases are typically diagnosed within the first two months of life due to the presence of pulmonary hypertension, heart failure, and recurrent pulmonary infections. The adult form is typically milder in clinical presentation with the Scimitar vein often found incidentally in otherwise healthy patients. Symptomatic young adults usually present with recurrent pulmonary infections and exertional dyspnea from pulmonary sequestration. The characteristic Scimitar vein is often demonstrated on chest x-ray (CXR) (see Figure 1).
Figure 1. Chest radiograph demonstrating Scimitar vein. https://commons.wikimedia.org/wiki/File:Scimitar_syndrome_chest_xray.jpg, licensed under the Creative Commons Attribution-Share Alike 4.0 International license.
The Scimitar vein produces a left to right shunt leading to excessive pulmonary blood flow and right heart dilation. Medical management centers on reducing excessive pulmonary blood flow to slow the progression to pulmonary hypertension and heart failure. Patients with the infantile form who exhibit signs of pulmonary hypertension require surgical correction. Other indications for surgical correction include a Qp:Qs greater than 1.5 in an asymptomatic patient, recurrent pneumonia, and heart failure.
Any preoperative anesthetic evaluation should include a review of cardiac imaging and functional studies given the high association of Scimitar syndrome with other congenital cardiac defects. Evaluation should also include the presence and severity of pulmonary hypertension, quantification of left to right shunt, baseline cardiopulmonary status, and degree of pulmonary hypoplasia. While the adolescent and adult forms tend to be milder in clinical presentation, the presence of recurrent infections, lung hypoplasia and longstanding pulmonary circulatory overload should be closely evaluated prior to anesthetic administration.
This patient’s history, clinical presentation, CXR, echocardiography and bronchoscopy strongly suggest a diagnosis of Scimitar syndrome. Though both sinus venosus atrial septal defect and Ebstein’s anomaly lead to right heart dilation, neither defect is typically associated with right lung hypoplasia.
REFERENCES
Midyat L, Demir E, Aşkin M, et al. Eponym. Scimitar syndrome. Eur J Pediatr. 2010;169(10): 1171-1177. doi:10.1007/s00431-010-1152-4.
Brown D, Geva T. Anomalies of the Pulmonary Veins. In: Shaddy R, Penny D, Feltes T, Cetta F and Mital S, eds. Moss and Adams’ Heart Disease in Infants, Children and Adolescents including the Fetus and Young Adult. 10th Edition. Philadelphia: Wolters Kluwer; 2022: 854-856.
Chowdhury UK, Anderson RH, Sankhyan LK, et al. Surgical management of the scimitar syndrome. J Card Surg. 2021; 36(10):3770-3795. doi:10.1111/jocs.15857
Stout KK, Daniels CJ, Aboulhosn JA, et al. 2018 AHA/ACC Guideline for the Management of Adults With Congenital Heart Disease: Executive Summary: A Report of the American College of Cardiology/American Heart Association Task Force on Clinical Practice Guidelines [published correction appears in J Am Coll Cardiol. 2019 May 14;73(18):2361]. J Am Coll Cardiol. 2019;73(12):1494-1563. doi:10.1016/j.jacc.2018.08.1028
