What Is Scimitar Syndrome?

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Scimitar syndrome is a rare, congenital (present at birth) heart defect that occurs in 1 to 3 out of every 100,000 live births. Babies with scimitar syndrome have an underdeveloped right lung and an underdeveloped right pulmonary artery.

They also have one or more pulmonary veins that carry blood into the right side of the heart instead of the left. This alters the natural flow of the circulatory system and inhibits the body's ability to acquire and use freshly oxygenated blood.

In some babies with scimitar syndrome, the right pulmonary artery is shaped like a scimitar (a curved sword). The heart may also be situated in a right-sided, abnormal position within the chest.

This article will discuss the causes and symptoms of scimitar syndrome, as well as the diagnostic procedure, treatment options, and prognosis.

A healthcare provider uses a stethoscope to check the heart health of a baby

AnnaStills / Getty Images

Underlying Anatomy

The heart, veins, and arteries are components of the circulatory system. The circulatory system's job is to supply oxygen and nutrients to the muscles, tissues, and organs of the body. The veins carry oxygen-depleted blood from the body to the heart.

The heart pumps oxygen-poor blood through the pulmonary arteries into the lungs, where it receives fresh oxygen. The pulmonary veins then carry the freshly oxygenated blood to the left side of the heart, where it gets pumped back out into the body.

History of Scimitar Syndrome

Scimitar syndrome was first identified during an infant autopsy in 1836. The first imaging diagnosis was made in 1949. Corrective surgery on an infant with this condition was first performed in 1950.

Types of Scimitar Syndrome

Since symptom severity varies significantly between infants and adults, this condition is classified into infantile and adult forms, as follows:

  • Infantile form: This form is categorized by the early onset of severe symptoms. Babies with the infantile form of scimitar syndrome have a mortality rate of up to 45%.
  • Adult form: This form is usually asymptomatic and typically requires no treatment. Adult form scimitar syndrome is often discovered during imaging exams for other conditions.


Scimitar syndrome symptoms range from nonexistent (asymptomatic) to severe in babies. Babies born with serious symptoms or cardiac complications, such as pulmonary hypertension (higher than normal pressure in the pulmonary artery) or pulmonary vein stenosis (narrowing), may be diagnosed in infancy.

Symptoms in babies include:

  • Cyanosis (blue or gray skin, lip, or nail color due to lack of oxygen)
  • Trouble breathing
  • Recurrent pneumonia (lung infection)
  • Tachypnea (rapid, shallow breathing)
  • Heart failure (the heart does not pump enough blood for the body's needs)

In adults, scimitar syndrome is typically asymptomatic but may cause complications, including heart failure, over time.

Symptoms in adults can include:


The cause or causes of scimitar syndrome are not known or fully understood. No specific gene has been identified to be at fault. However, heredity may play a role.

A 2022 case study identified three members of the same family with scimitar syndrome. The researchers concluded that scimitar syndrome may be inherited in some instances through an autosomal dominant inheritance pattern.

This inheritance pattern requires only one copy of a mutated (changed) gene from one parent. A child with a parent who has the mutated gene has a 50% chance of inheriting the same mutation. "Autosomal" means the gene is on a chromosome other than the sex chromosomes, X or Y. Therefore, children of any sex are equally at risk.


Diagnosis of scimitar syndrome is usually made through imaging tests, such as a chest X-ray or computed tomography (CT) scan. These tests provide images of the size, shape, and positioning of the pulmonary arteries, lungs, and heart.

Babies may be given imaging tests if they have symptoms of scimitar syndrome. They may also be tested if their weight gain and physical growth are significantly slower than normal (failure to thrive).

Asymptomatic adults or adults with mild symptoms may learn they have scimitar syndrome for the first time after having an imaging test for another purpose.


Scimitar syndrome Is repaired surgically in babies. Several surgical techniques can be utilized to reroute the pulmonary vein and correct blood flow. Part of the lung may also be removed as part of treatment.

One surgical technique is called a baffling procedure. The surgeon will artificially construct a tunnel within the heart or blood vessels that enables the redirection of blood flow. Alternatively, blood flow may be rerouted through the implantation of the anomalous veins directly into the left side of the heart.

Treatment for scimitar syndrome is not typically required in asymptomatic adults. Adults with ongoing or severe symptoms may also require surgery.


In symptomatic infants, treatment is required in order to achieve a good prognosis. A successful surgery typically enables long-term survival and healthy life.

Surgery for scimitar syndrome can, however, be challenging and difficult, especially for young babies. Complications, such as narrowing of the pulmonary vein (pulmonary vein stenosis) and surgical mortality (death), are possible.

For these reasons, the timing of the surgery is crucial and must be weighed against multiple factors, such as your baby's current condition.


Your coping ability will be significantly enhanced if you lean on or create a support system. Your baby's healthcare providers can be part of this team. Make sure to ask as many questions as you need and get second opinions as necessary.

If you have people in your life, such as a partner, trusted family members, or friends, make them part of your team. Don't underestimate the power of a shoulder to lean on.

Working with a therapist or a support group of people going through similar experiences can be highly beneficial.

Coping requires that you take care of yourself. Do your best to get enough sleep and exercise daily. Try to eat healthy food, rather than fast food, during this time.

Meditation, yoga, and activities that provide stress relief will also be beneficial.


Scimitar syndrome is a type of rare congenital heart defect. Babies born with this condition may be asymptomatic, or have severe symptoms which require surgical correction.

Adults with this condition are often asymptomatic. If symptoms such as persistent lung infections occur, surgery may also be necessary to correct scimitar syndrome in this population.

A Word From Verywell

If you're the parent or caregiver of a baby with scimitar syndrome, you may find yourself in the unwanted position of having to make scary decisions about their care. You may also need to find the balance between taking care of your baby and taking care of yourself. None of this is easy.

Try to remember and believe that there is no one and nothing to blame for this situation. Nothing you did or didn't do created scimitar syndrome in your child. Life is full of challenges. You may never have visualized this one, but with support, you can get through this time.

7 Sources
Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
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  2. Genetic and Rare Diseases Information Center. Pulmonary venous return anomaly.

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  5. Althomali SA, Alhefny AA, Almalki MS. Uncommon presentation of adult-form scimitar syndrome associated with single left pulmonary vein in a pregnant woman. BMJ Case Rep. 2017;2017:bcr2017219952. doi:10.1136/bcr-2017-219952

  6. Mahendran Arjun, Saidi Arwa, Maegawa Gustavo, et al. Scimitar syndrome: a family matter. JACC. 2020;75(11_Supplement_1):2409. doi:10.1016/S0735-1097%2820%2933036-9

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By Corey Whelan
Corey Whelan is a freelance writer specializing in health and wellness conntent.