What Is Scimitar Syndrome?

  • Barbara TimkovaBachelor in Biomedical Sciences- BSc (Hons), Queen Mary University of London


Scimitar syndrome is a rare heart defect that infants are born with. It results in an anomalous pulmonary venous return of oxygenated blood from the left lung is being returned to the wrong side of the heart. The majority of babies are treated with heart surgery, though some patients will never require surgical treatment.1 

An interdisciplinary team approach involving a paediatrician, paediatric cardiologist, cardiac surgeon, and radiologist is necessary for treating a patient with scimitar syndrome. 

Scimitar syndrome can have severe consequences if it isn't detected in the early stages, particularly in the infantile form.1 

The surgical approach is made easier by an early diagnosis thanks to advanced imaging. This lowers the rates of morbidity and death following corrective surgery. A longer follow-up is required. Though some patients may develop the symptoms later in adolescence, which is in general less problematic and can be treated by various surgical approaches.1

Background information

Scimitar syndrome is a rare disorder of a physical abnormality present from birth (also called "congenital venolabar” disorder). The pulmonary vein from the right lung is unusually connected to the heart, allowing oxygenated blood from the lung to return to the wrong side of the heart (to right side instead of the left side). This causes an overburden and an abnormal enlargement of the right half of the heart, which, in time, could prompt heart failure.1

Incidence of Scimitar syndrome

The incidence of scimitar syndrome is approximately 1-3 in 100,000 life births1, which makes it a relatively rare heart defect. However, it is believed that the incidence is higher. Females are predominant, with a female-to-male ratio of 2 to 1.1

 History of scimitar syndrome

  • The first case of scimitar syndrome was described in 1836 by George Cooper when conducting an autopsy of a 10-month-old infant
  • The first imaging diagnosis was described by Dotter et al. in 1949
  • The first surgical intervention involved a resection of the left lower lung in 1950
  • The first ever corrective surgery was performed in 19561

Why "scimitar"?

The name originates from the curvilinear shadow made by the anomalous scimitar vein on the chest radiograph.4

The term “scimitar” itself means “a sword with a curved blade that is sharp only on its outer edge and gets wider towards its pointed end."3

Causes and risk factors

Causes of scimitar syndrome

It is currently not fully understood how the development of scimitar syndrome occurs. Yet, it is believed that it is connected to an embryological error in the fundamental development of the lung bud in the early stages of embryogenesis.1

Possible risk factors

Some factors may indeed increase the chances of being born with scimitar syndrome.

These factors include:

  • Genetics
  • Smoking or drinking during pregnancy
  • Taking anti-acne medications like Isotretinoin during pregnancy5

Symptoms and diagnosis

Immediate symptoms after birth

Sometimes, babies can show scimitar syndrome symptoms right after being born.

These symptoms include:

  • Irregular/rapid breathing
  • Grey or pale skin
  • Excessive swelling around eyes, legs and stomach5

Symptoms in adulthood

It can also be seen that some babies can grow into adulthood without showing any of the symptoms. Therefore, the majority of adults with scimitar syndrome remain without symptoms.

Those showing the symptoms usually experience:

Characteristics of skimitar syndrome patients

Most of the people born with this syndrome share common characteristics:

  • Displacement of the heart to the right (dextraposition)
  • An unusual systemic blood supply to the right lung
  • Associated with right lung and pulmonary artery hypoplasia
  • Right lung anomalous curved venous drainage, either fully or partially, to the inferior vena cava1


Pre-born ultrasound diagnosis 

The earliest detection of a heart defect was identified in week 20. However, the baby cannot be diagnosed before being born because of the need for further examinations by specialists.6

Diagnosis after birth

Doctors or healthcare providers can use different methods to diagnose a patient with scimitar syndrome. 

The most common methods include:

  • Chest x-ray to produce a picture inside the body of the heart, lungs and vessels
  • CT scan to produce detailed images of the body's organs
  • Angiography to check the blood vessels1

The importance of early detection 

Experts say that it is important to detect a baby with scimitar syndrome as early as possible, allowing the medical therapy to start promptly. Early detection benefits the baby's optimal growth until further interventions.1

Treatment and complications

Surgical approach

Depending on the anatomical and pathologic characteristics of each patient, the surgical strategy for treating scimitar syndrome differs. In general, it includes a correction of the blood flow to and from the heart. 

Surgical treatment can be achieved by:

  • Resecting the right lung drained by the atypical scimitar vein
  • Correction resulting in a re-routed blood flow1 

Corrective surgical techniques can be achieved by:

  • Creating a tunnel within a heart to redirect blood flow
  • direct reimplantation of the abnormal pulmonary venous drainage to the left atrium, either with or without cardiac arrest1

There are many other surgical approaches that are highly specific to the patient's needs. 

Surgery complications

Possible complications include:

  • Mortality
  • Need for re-interventions
  • Complications during the surgery
  • Decrease of blood flow to the right lung
  • Pulmonary vein obstruction1


Can I reduce the risk of having a baby with scimitar syndrome? 

Because the heredity of scimitar syndrome is not yet understood6, it is not possible to prevent having a baby with scimitar syndrome. 

You can increase your chances of having a healthy baby by:

  • stop drinking any alcohol
  • stop smoking
  • take suggested vitamin supplies
  • Have enough movement
  • Avoid stress7


In the past, the infantile form had a poor future. These days, the results of corrective surgery are usually favourable, with a low risk of morbidity and death following the procedure as a result of early diagnosis and a well-established surgical technique.1


Scimitar syndrome is an uncommon congenital cardiac condition. Both the pulmonary arteries and the right lung are affected. Some infants might not exhibit any signs of the illness, and others may require heart surgery within the first two months of being born. In order to treat the narrowing of the redirected veins, babies who need early surgery can require further procedures and examinations. Adults with scimitar syndrome can lead normal lives without requiring surgery in certain cases, although they may have symptoms like lung infections. 


  1. Diaz-Frias J, Widrich J. Scimitar syndrome. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2023 [cited 2023 Oct 22]. Available from: http://www.ncbi.nlm.nih.gov/books/NBK546602/
  2. Scimitar syndrome | children’s wisconsin [Internet]. [cited 2023 Oct 22]. Available from: https://childrenswi.org/medical-care/herma-heart/for-medical-professionals/pediatric-heart-surgery/scimitar-syndrome
  3. Scimitar [Internet]. 2023 [cited 2023 Oct 25]. Available from: https://dictionary.cambridge.org/dictionary/english/scimitar
  4. Dasari N, Valapala VNG, Anim R. Scimitar syndrome – An incidental diagnosis in a case of fibroadenoma. Radiology Case Reports [Internet]. 2022 Jun 1 [cited 2023 Oct 25];17(6):2231–4. Available from: https://www.sciencedirect.com/science/article/pii/S1930043322002515
  5. Clinic [Internet]. [cited 2023 Oct 26]. Scimitar syndrome: causes, symptoms and treatment. Available from: https://my.clevelandclinic.org/health/diseases/22747-scimitar-syndrome
  6. Scimitar syndrome - an overview | sciencedirect topics [Internet]. [cited 2023 Oct 26]. Available from: https://www.sciencedirect.com/topics/medicine-and-dentistry/scimitar-syndrome
This content is purely informational and isn’t medical guidance. It shouldn’t replace professional medical counsel. Always consult your physician regarding treatment risks and benefits. See our editorial standards for more details.

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Barbara Timkova

Bachelor in Biomedical Sciences- BSc (Hons), Queen Mary University of London

I am a biomedical student interested in medical genetics, specifically in genetics behind cancer. I have a strong background of volunteering in hospitals, vaccination centres and in organizing fundraising events for cancer research.

I also help in recruiting blood and bone marrow donors for leukaemia patients. The favourite part of my degree is working in labs because I can apply my knowledge and observe the cells with my own eyes.

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