Cor Triatriatum

Cor triatriatum is a heart defect that’s present at birth (congenital), in which a membrane divides one of your child’s top heart chambers (atria) into two separate sections. This membrane makes it harder for blood to flow normally through your child’s heart. The membrane may have an opening that lets some blood through. But if there isn’t one, or if the opening is small, blood can back up in your child’s heart. This may lead to heart failure and other complications.

On an echo test, cor triatriatum makes it look like your child has three atria, rather than the expected two. That’s how the condition gets its name. Cor triatriatum comes from the Latin for “heart with three atria.”

There are two main types of this condition based on where the membrane is located. With cor triatriatum sinister, the membrane is in the left atrium. With cor triatriatum dexter, the membrane is in the right atrium.

This is a rare condition. Experts estimate that cor triatriatum accounts for 1 to 4 in every 1,000 cases of congenital heart disease.

Symptoms of cor triatriatum

Symptoms usually appear in infancy or early childhood. Your child may have:

• Trouble breathing or fast breathing
• Slower weight gain than expected
• Extreme sleepiness
• A cough that produces blood
• Swelling in their legs, feet or belly

Call a healthcare provider right away if you notice any of these symptoms.

Rarely, this condition causes no symptoms until adulthood. These may include:

• Chest pain or discomfort
• Coughing up blood
• Fainting
• Heart palpitations
• Tiring easily
• Trouble breathing, especially during physical activity or when lying down
• Swelling in the legs or belly

Cor triatriatum causes

Changes that occur during fetal development cause cor triatriatum. These changes result in a membrane forming in one of the top heart chambers.

Experts are still exploring exactly which changes cause cor triatriatum sinister. A leading theory is that the common pulmonary vein doesn’t merge with the left atrium as it should. Something goes wrong in the process. This causes the membrane to form.

With cor triatriatum dexter, fetal heart tissue that normally goes away on its own instead stays in place and forms the membrane. 

Cor triatriatum has no known genetic causes. There’s also no evidence that it’s passed down within families (hereditary).

Associated heart defects

Some babies with cor triatriatum also have other heart defects. These include:

• A hole between their top heart chambers (atrial septal defect)
• Pulmonary veins that connect to the wrong side of their heart (total or partial anomalous pulmonary venous return)

Complications of this condition

Cor triatriatum disrupts normal blood flow through your child’s heart. This can lead to serious complications, like:

• Abnormal heart rhythms in their top chambers (atrial arrhythmias)
• Leaky heart valve on the right side of their heart (tricuspid regurgitation)
• Problems with their heart’s pumping ability (heart failure)
• Raised pressure in their pulmonary arteries (pulmonary hypertension)
• Sudden stopping of their heart (cardiac arrest)

How doctors diagnose this condition

Healthcare providers diagnose cor triatriatum with a physical exam and testing. Your child’s provider will:

• Listen to their heart and lungs with a stethoscope
• Look for visible signs of heart problems, like swelling in your child’s belly or legs
• Run imaging tests to see the structure of your child’s heart and check for complications

Your child may need one or more of these tests:

• Chest X-ray
• Echocardiogram (echo)
• Heart CT scan
• Heart MRI scan

Healthcare providers sometimes diagnose cor triatriatum in adults. This can happen if symptoms develop or signs appear on an imaging test done for another reason.

Cor triatriatum types

There are two main types of cor triatriatum:

• Cor triatriatum sinister: The membrane is located in the left atrium. One section contains the pulmonary veins. These vessels receive blood from the lungs. The other contains the mitral valve. This “door” sends blood down to the left ventricle. Most people have this type.
• Cor triatriatum dexter: The membrane is located in the right atrium. This type is very rare.

Cor triatriatum sinister further breaks down into three groups. These are based on what the membrane looks like:

• Group 1: There’s no opening in the membrane to let blood flow from the left atrium to the left ventricle. Blood must take a different route instead — possibly through a patent foramen ovale. This is a hole between the top chambers that normally closes after birth.
• Group 2: There is one or more openings in the membrane. But they’re very small. This means it’s hard for blood to flow down to the left ventricle.
• Group 3: There’s one hole and it’s large enough for blood to easily pass through.

Groups 1 and 2 are more severe and cause symptoms early in life. These are the most common groups. Group 3 is milder and less common. It usually doesn’t cause symptoms until adulthood, if at all.

How is cor triatriatum treated?

Surgery is the main treatment for cor triatriatum. Your child’s care team will describe the exact details. These can vary based on the anatomy of your child’s heart, including any other heart defects they have.

In general, a surgeon will remove the membrane that divides the left or right atrium. This allows blood to flow better through your child’s heart. They may also repair other heart issues at the same time.

Adults who are diagnosed but don’t have symptoms may not need surgery right away. Healthcare providers monitor the condition and decide the best time for surgery.

When should I call a healthcare provider?

Seek medical attention right away if your child has trouble breathing or any other symptoms of cor triatriatum. Keep in mind that there are many possible causes for these issues. Your child doesn’t necessarily have a heart defect. But if they do, seeking care quickly can help them get the care they need.

If you suspect you may have cor triatriatum or another undiagnosed heart defect as an adult, reach out to a healthcare provider.

What can I expect if my child has cor triatriatum?

Your child’s outlook depends on many factors, including any other heart defects they have. Their care team can give you the best sense of what you might expect.

In general, many children and adults do well after surgery to treat cor triatriatum. Surgery can help blood flow normally through the heart and relieve symptoms. Anyone with this condition needs routine follow-up visits with a heart doctor (cardiologist) throughout their life.