What is a cardiac shunt?
A cardiac shunt is an irregular pattern of blood flow in your heart. You may have a cardiac shunt along with typical blood flow patterns. Or you may have a cardiac shunt in place of a typical blood flow pattern. A shunt is a passage by which blood moves from one area (blood vessel or heart chamber) to another in a pattern that isn't normal.
A cardiac shunt is a congenital heart defect, meaning it’s present at birth. Cardiac shunt symptoms can vary widely. Some people have no signs of a cardiac shunt, while other shunts can be fatal. When babies are born with a severe cardiac shunt, healthcare providers usually treat it in the first few months of life.
How does blood typically flow through your heart?
Usually, blood flows through your heart in a series of steps:
- Oxygen-poor blood enters the right side of your heart.
- Your heart pumps blood into and through your lungs.
- Your lungs fill the blood with oxygen and take out carbon dioxide as you breathe.
- The oxygen-rich blood flows from your lungs to the left side of your heart.
- Blood pumps from your heart into your aorta, the large artery that carries oxygenated blood to the rest of your body.
With a cardiac shunt, blood doesn’t flow through these steps. Oxygenated blood may leak back into your lungs. Or oxygen-poor blood may not reach your lungs.
What are the types of cardiac shunts?
Cardiac shunts may be:
- Left-to-right (acyanotic): This type of shunt doesn't affect the process of oxygenation in your lungs.
- Right-to-left (cyanotic): This type of shunt interrupts blood flow and oxygenation in your lungs. In these situations, you may have lower oxygen saturation in your blood or a bluish tinge to your skin.
Left-to-right cardiac shunt
In left-to-right shunts, blood that’s already oxygenated leaks backward to your lungs. Examples of left-to-right cardiac shunts include:
- Atrial septal defect (ASD).
- Atrioventricular septal defect.
- Patent ductus arteriosus (PDA).
- Total/partial anomalous pulmonary venous return (TAPVR/PAPVR).
- Ventricular septal defect (VSD).
Right-to-left cardiac shunt
In right-to-left shunts, oxygen-poor blood doesn’t always go to your lungs. Instead, it may flow directly back to the rest of your body. Examples of right-to-left cardiac shunts include:
- Double outlet right ventricle.
- Eisenmenger syndrome.
- Hypoplastic left heart syndrome (HLHS).
- Pulmonary arteriovenous malformation.
- Pulmonary atresia.
- Tetralogy of Fallot.
- Transposition of the great arteries.
- Truncus arteriosus.
Circular shunts are severe, life-threatening conditions. In a circular shunt, blood circulates through your heart without sending enough blood to the rest of your body. Circular shunts most commonly appear in severe forms of Ebstein’s anomaly (EA).
How common are cardiac shunts?
Cardiac shunts are the most common type of congenital heart defect. About 1 in every 100 babies are born with a congenital heart defect.
Symptoms and Causes
What causes a cardiac shunt?
Sometimes, cardiac shunts have a genetic component. You may have a cardiac shunt due to a change (mutation) in a specific gene. For example, up to half of people born with Down syndrome also have a type of cardiac shunt.
Some factors during pregnancy can also affect the chances of having a baby with a cardiac shunt. Babies have a higher risk of a cardiac shunt if their birthing parent had:
- Gestational diabetes.
- High exposure to ibuprofen or vitamin A.
- Influenza (flu).
- Marijuana use.
- Rubella (German measles).
What are the symptoms of a cardiac shunt?
Cardiac shunt symptoms can vary significantly. Left-to-right shunts often don’t cause any symptoms until you’re a teenager or adult. When symptoms develop, they may include:
- Shortness of breath (dyspnea).
- Quick fatigue or inability to exercise.
Over time, left-to-right shunts may cause pulmonary hypertension (high blood pressure in your pulmonary arteries).
In right-to-left shunts, babies usually have symptoms that start early. One of the most common symptoms of a right-to-left shunt is a baby that looks blue (cyanosis). Other symptoms include:
- Clubbed fingers or toenails.
- Coughing up blood (hemoptysis).
- Poor weight gain.
- Shortness of breath (dyspnea).
- Repeat infections.
Diagnosis and Tests
How is a cardiac shunt diagnosed?
To diagnose a cardiac shunt, your healthcare provider may use tests such as a:
- Blood test: Blood tests look for changes in your red blood cells.
- Imaging tests: A chest X-ray or CT scan looks for physical changes to your heart’s shape.
- Echocardiogram: An echocardiogram looks at your heart’s structure and function.
- Electrocardiogram (EKG): An electrocardiogram (EKG) looks for signs of pulmonary hypertension or other issues.
- Cardiac catheterization: Cardiac catheterization assesses the pressure in each heart chamber. You may need cardiac catheterization to determine the need for surgery, or if your provider has already recommended surgery to treat the shunt.
Management and Treatment
How is a cardiac shunt treated?
Cardiac shunt treatment varies depending on symptoms and severity. Small shunts may clear up (resolve) without treatment. Your healthcare provider may operate on a larger shunt to redirect blood flow. Common heart shunt surgeries include:
- Norwood procedure: This is an open-heart surgery typically done on newborns. Surgeons create a larger aorta and redirect blood flow. After surgery, the right ventricle can do all the work of pumping blood out to the body.
- Glenn procedure: Your surgeon redirects blood flow, so blood coming from your body goes directly to your lungs.
- Fontan procedure: Your surgeon redirects blood flow so oxygen-poor blood goes directly to your lungs. Post-surgery, oxygen-rich blood goes directly to one heart ventricle. This prevents oxygen-poor and oxygen-rich blood from mixing in your heart’s ventricles.
How can I prevent a cardiac shunt?
There’s no guaranteed way to prevent a cardiac shunt. If you're pregnant, you can increase your overall chances of having a healthy baby by practicing healthy habits. You may:
- Avoid harmful substances, including alcohol, tobacco, illegal drugs and excessive amounts of caffeine.
- Eat a nutritious diet and avoid certain foods, such as rare meat, soft cheeses and unpasteurized animal products, which could raise the risk of infection.
- Exercise regularly.
- Schedule all vaccines, including your flu shot, as recommended by your healthcare provider.
- Sleep at least seven to eight hours nightly. Try to sleep on your left side to increase blood flow.
- Take prenatal vitamins and any other supplements as directed by your healthcare provider.
Outlook / Prognosis
What is the outlook if you have a cardiac shunt?
Cardiac shunts vary widely, and so does the outlook. Larger or more severe cardiac shunts need treatment to avoid complications. Some types require surgical treatment within the first few weeks of birth. If you develop severe pulmonary hypertension, you're more likely to need heart shunt surgery or experience complications.
Many times, shunts that don’t affect the process of blood oxygenation don't cause severe complications. They may not cause symptoms at all or require any treatment.
What else should I ask my healthcare provider?
You may also want to ask your healthcare provider:
- What type of cardiac shunt do I have?
- What tests do I or my baby need to diagnose a cardiac shunt?
- What are the treatment options?
- What can I do to reduce my risk of complications from a cardiac shunt?
- What are the chances that my baby will have a cardiac shunt?
- What can I expect to happen down the road?
A note from Cleveland Clinic
Cardiac shunts are irregular patterns of blood flow in your heart. They’re often genetic, although some are linked to pregnancy factors. Shunt symptoms vary widely. Some types of shunts cause few to no symptoms. Others are severe and can be life-threatening without treatment. If a cardiac shunt is severe, your healthcare provider may operate to create a new path for blood flow.
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