Scimitar Syndrome

Scimitar syndrome is a rare congenital heart defect. Babies with scimitar syndrome are born with an underdeveloped right lung and pulmonary artery. They often need surgery to repair their heart. Many adults live healthy lives with scimitar syndrome. If they experience severe shortness of breath or repeat lung infections, they may need surgery.


What is scimitar syndrome?

Scimitar syndrome is a congenital (present at birth) heart defect. It’s a type of partial anomalous pulmonary venous return (PAPVR).

In scimitar syndrome, people have:

  • Hypoplastic (underdeveloped) right lung.
  • Hypoplastic (underdeveloped) right pulmonary artery (the blood vessel that carries blood to their lungs).

In about 1 in 3 people with scimitar syndrome, their right pulmonary vein is shaped like a scimitar, a curved Middle Eastern sword. Healthcare providers can see this shape on imaging.


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How does a healthy heart pump blood?

A healthy heart takes in blood from your body and pumps it to your lungs. In your lungs, blood collects oxygen to carry back to your heart and the rest of your body.

A network of blood vessels called the circulatory system carries blood throughout your body. Blood circulates through two types of blood vessels:

  • Arteries carry oxygen-rich blood from your heart to other parts of your body.
  • Veins carry oxygen-poor blood from other parts of your body back to your heart.

How do the pulmonary arteries and veins work?

Your pulmonary arteries and veins carry blood in and out of your lungs. The process has a few steps:

  1. Your pulmonary arteries carry oxygen-poor blood from the right side of your heart to your lungs.
  2. Your lungs oxygenate the blood.
  3. Your pulmonary veins carry this oxygen-rich blood back to the left side of your heart.
  4. The left side of your heart pumps out this blood to the rest of your body.

How does scimitar syndrome affect my body?

In scimitar syndrome, one or more of your pulmonary veins carries blood into the right side of your heart instead of the left side.

Sometimes, your right lung may also receive blood from your aorta instead of your pulmonary arteries. Your aorta is supposed to carry blood to the rest of your body.

How common is scimitar syndrome?

Scimitar syndrome is rare. Only about 1 to 3 out of every 100,000 babies are born with the condition. It’s twice as common in females as in males.


Symptoms and Causes

What causes scimitar syndrome?

Often, experts don’t know exactly what causes scimitar syndrome. Some factors can increase the risks that your baby will have a congenital heart defect. These risks include:

  • Genetics.
  • Medications like the acne medicine isotretinoin (Accutane®).
  • Environmental factors like smoking or drinking alcohol during pregnancy.

What are the symptoms of scimitar syndrome?

Sometimes, babies show scimitar syndrome symptoms immediately after birth. These symptoms include:

  • Difficulty breathing while feeding.
  • Pale or grayish skin (cyanosis).
  • Rapid breathing.
  • Swelling (edema) in their legs, belly or around their eyes.

Other times, babies may grow into adulthood without showing any symptoms. Most adults with scimitar syndrome remain asymptomatic (show no symptoms). Adults who do have symptoms commonly experience:

Diagnosis and Tests

What tests are used to diagnose scimitar syndrome?

Healthcare providers may use several tests to identify scimitar syndrome. These imaging tests tell providers about the size of your right lung and right pulmonary artery:

  • Chest X-rays use radiation to take images of your heart, lungs, airways and blood vessels.
  • CT scans take X-rays from multiple angles to create detailed images of the inside of your body.
  • MR angiography uses radio waves, magnets and a computer to assess your blood vessels.
  • Transthoracic echocardiograms (TTE) use ultrasounds to evaluate your heart and chest wall.

Your provider may also do cardiac catheterization, where they inject dye to look at your blood vessels and measure the pressures in your lungs and your body.

Management and Treatment

How is scimitar syndrome treated?

Healthcare providers treat scimitar syndrome with surgery. If a provider spots the condition in a baby, they usually operate within the first two months of life. Adults who have scimitar syndrome only need surgery if they have severe symptoms like repeat lung infections.

During surgery, a cardiac surgeon (heart doctor who does surgery) may:

  • Reroute the pulmonary vein to the left side of your heart using patches.
  • Reroute the pulmonary vein to the left side by implanting it directly into the left side of your heart.
  • Remove the hypoplastic lung (pneumectomy).


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

There's no way to prevent having a child with scimitar syndrome. You can increase your chances of having a healthy baby by:

  • Avoiding harmful substances like alcohol, recreational drugs or nicotine, during pregnancy.
  • Discussing the risks and benefits of any medications with your healthcare provider.
  • Getting a rubella vaccine, as rubella infection can affect your baby’s heart development.
  • Managing chronic conditions like diabetes.
  • Taking folic acid and other prenatal vitamins as directed.

Outlook / Prognosis

What is the outlook for people with scimitar syndrome?

People who have surgery for scimitar syndrome typically have excellent long-term outcomes. Most people experience no further symptoms of scimitar syndrome after surgery. Some people, especially babies and young children, may develop some narrowing of the rerouted pulmonary vein, which could require additional treatment.

Some adults with scimitar syndrome experience no symptoms. However, many adults who have scimitar syndrome have other heart conditions that require treatment. These conditions may affect their quality of life. Adults may eventually need surgery if they begin showing symptoms of scimitar syndrome like severe shortness of breath or lung infections. Adults also may require special studies to determine whether they have elevated lung artery pressures.

What conditions are related to scimitar syndrome?

Many people with scimitar syndrome have other cardiovascular problems. Some are born with multiple heart conditions. Or scimitar syndrome may lead to other complications.

People with other heart conditions may have:

  • Atrial septal defects (ASD): Holes between the two upper chambers of your heart.
  • Horseshoe lung: When two parts of your lungs connect atypically.
  • Pulmonary hypertension: When the pressures in your lung arteries are very high.
  • Pulmonary sequestration (accessory lung): A piece of disconnected lung tissue that doesn’t function or has an abnormal blood supply.
  • Tetralogy of Fallot: A common defect that requires treatment in infancy to provide blood to your lungs.
  • Ventricular septal defects (VSD): A hole between the two pumping chambers of your heart.

Living With

What else should I ask my doctor?

You may want to ask your healthcare provider:

  • What is the most likely cause of scimitar syndrome?
  • Do I need surgery for scimitar syndrome?
  • What happens if I don’t have surgery?
  • How can I manage my heart health with scimitar syndrome?
  • What are the chances that I'll have a child with scimitar syndrome if I have the condition?
  • What are the chances that I'll have a second child with scimitar syndrome?

A note from Cleveland Clinic

Scimitar syndrome is a rare congenital heart defect. It affects the right lung and pulmonary arteries. Some babies may show no symptoms of the condition. Others may need surgery in their first two months of life. Babies that need early surgery may need additional surgery to address the narrowing of the rerouted veins. Some adults who have scimitar syndrome may live healthy lives without needing surgery. Most adults who have surgery for scimitar syndrome have excellent outcomes with typical life expectancy.

Medically Reviewed

Last reviewed by a Cleveland Clinic medical professional on 04/11/2022.

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