By Mayo Clinic Staff
Atrioventricular canal defect is a combination of heart problems resulting in a defect in the center of the heart. The condition occurs when there's a hole between the heart's chambers and problems with the valves that regulate blood flow in the heart.
Sometimes called endocardial cushion defect or atrioventricular septal defect, atrioventricular canal defect is present at birth (congenital). The condition is often associated with Down syndrome.
Atrioventricular canal defect allows extra blood to flow to the lungs. The extra blood forces the heart to overwork, causing the heart muscle to enlarge.
Untreated, atrioventricular canal defect can cause heart failure and high blood pressure in the lungs. Doctors generally recommend surgery during the first year of life to close the hole in the heart and to reconstruct the valves.
Atrioventricular canal defect can involve only the two upper chambers of the heart (partial) or all four chambers (complete). In either type, extra blood circulates in the lungs.
Complete atrioventricular canal defect
Signs and symptoms usually develop in the first several weeks of life. These signs and symptoms are generally similar to those associated with heart failure and might include:
- Difficulty breathing or rapid breathing
- Lack of appetite
- Poor weight gain
- Pale skin color
- Bluish discoloration of the lips and skin
- Excessive sweating
- Irregular or rapid heartbeat
- Swelling in the legs, ankles and feet
Partial atrioventricular canal defect
Signs and symptoms might not appear until early adulthood and might be related to complications that develop as a result of the defect. These signs and symptoms can include:
- Abnormal heartbeat (arrhythmia)
- Shortness of breath
- High blood pressure in the lungs (pulmonary hypertension)
- Heart valve problems
- Heart failure
When to see a doctor
See your doctor if you or your child develops signs or symptoms of atrioventricular canal defect.
Atrioventricular canal defect occurs before birth when a baby's heart is developing. Some factors, such as Down syndrome, might increase the risk of atrioventricular canal defect. But the cause is generally unknown.
The normal-functioning heart
The heart is divided into four chambers, two on the right and two on the left.
The right side of your heart moves blood into vessels that lead to the lungs. There, oxygen enriches the blood. The oxygen-rich blood flows back to your heart's left side and is pumped into a large vessel (aorta) that circulates blood to the rest of your body.
Valves control the flow of blood into and out of the chambers of your heart. These valves open to allow blood to move to the next chamber or to one of the arteries, and close to keep blood from flowing backward.
What happens in atrioventricular canal defect
In partial atrioventricular canal defect:
- There's a hole in the wall (septum) that separates the upper chambers (atria) of the heart
- Often the valve between the upper and lower left chambers (mitral valve) also has a defect that causes it to leak (mitral valve regurgitation)
In complete atrioventricular canal defect:
- There's a large hole in the center of the heart where the walls between the atria and the lower chambers (ventricles) meet. Oxygen-rich and oxygen-poor blood mix through that hole.
- Instead of separate valves on the right and left, there's one large valve between the upper and lower chambers.
- The abnormal valve leaks blood into the ventricles.
- The heart is forced to work harder and enlarges.
Factors that might increase a baby's risk of developing atrioventricular canal defect before birth include:
- Down syndrome
- German measles (rubella) or another viral illness during a mother's early pregnancy
- Alcohol consumption during pregnancy
- Poorly controlled diabetes during pregnancy
- Smoking during pregnancy
- Certain medications taken during pregnancy — talk to your doctor before taking any drugs while you're pregnant or trying to become pregnant
- Having a parent who had a congenital heart defect
Complications of atrioventricular canal defect can include:
- Enlargement of the heart. Increased blood flow through the heart forces it to work harder than normal, causing it to enlarge.
- Pulmonary hypertension. When the heart's left ventricle weakens and can't pump out enough blood, pressure builds and backs up through blood vessels in the lungs, causing high blood pressure in the lungs.
- Respiratory tract infections. Atrioventricular canal defect can cause recurrent bouts of lung infections.
- Heart failure. Untreated, atrioventricular canal defect usually results in the heart's inability to pump enough blood to meet the body's needs.
Complications later in life
Treatment greatly improves the outlook for children with atrioventricular canal defect. However, some children who have corrective surgery may still be at risk later in life of:
- Leaky heart valves
- Narrowing of the heart valves
- Abnormal heart rhythm
- Breathing difficulties associated with lung damage
Common signs and symptoms of these complications include:
- Shortness of breath
- Rapid, fluttering heartbeat
Additional surgery might be needed to correct complications of atrioventricular canal defect.
You or your child might be referred to a doctor trained in heart conditions (cardiologist).
What you can do
- Write down symptoms you or your child experiences, including any that may seem unrelated to the reason why you scheduled the appointment.
- Make a list of all your medications, vitamins and supplements.
- Write down key medical information, including other conditions.
- Write down key personal information, including any recent changes or stressors in your life.
- Write down questions to ask your doctor.
- Find out if your family has a history of heart disease.
Questions to ask your doctor
Preparing a list of questions can help you make the most of your time with your doctor, and ensure that you cover all of the points that are important to you. For atrioventricular canal defect, some basic questions to ask your doctor include:
- What's the most likely cause of my symptoms or my baby's symptoms?
- What tests are needed? Is there any special preparation for them?
- What kind of treatment do you recommend?
- How can we manage other health problems together with atrioventricular canal defect?
In addition to the questions that you've prepared to ask your doctor, don't hesitate to ask other questions during your appointment.
What to expect from your doctor
Your doctor is likely to ask you a number of questions. Being ready to answer them may leave time to go over points you want to spend more time on. You may be asked questions such as:
- When did you first notice symptoms? Are they continuous or occasional?
- Does anything seem to improve or worsen these symptoms?
- Is there a family history of congenital heart disease?
- Did you have diabetes or a viral infection, such as measles, during your pregnancy?
- Were any medications taken during pregnancy?
- Was there tobacco or alcohol use during pregnancy?
Atrioventricular canal defect might be detected before birth through ultrasound and special heart imaging.
After birth, signs and symptoms of complete atrioventricular canal defect are usually noticeable within the first few weeks. When listening to your baby's heart, your doctor might hear an abnormal whooshing sound (heart murmur) caused by turbulent blood flow.
If your baby is experiencing the signs and symptoms of atrioventricular canal defect, your doctor might recommend:
- Electrocardiogram (ECG or EKG). Electrical signals are recorded as they travel through the heart. Your doctor can look for patterns that indicate abnormal heart function.
- Echocardiogram. Sound waves produce live-action images of the heart. Echocardiogram can reveal a hole in the heart and abnormal heart valves, as well as abnormal blood flow through the heart.
- Chest X-ray. The image can show evidence of an enlarged heart.
- Cardiac catheterization. A thin, flexible tube (catheter) is inserted into a blood vessel in the groin and up to the heart. A dye injected through the catheter makes the heart structures visible on X-ray pictures. The catheter also allows the doctor to measure pressure in the chambers of the heart and in the blood vessels.
Surgery is needed to repair complete and partial atrioventricular canal defects. The procedure involves closing the hole in the septum with one or two patches. The patches stay in the heart permanently, becoming part of the septum as the heart's lining grows over them.
For a partial atrioventricular canal defect, surgery also involves repair of the mitral valve, so it will close tightly. If repair isn't possible, the valve might need to be replaced.
For a complete atrioventricular canal defect, surgery also includes separation of the single valve into two valves, on the left and right sides of the repaired septum. If separating the single valve isn't possible, heart valve replacement might be needed.
If the heart defect is repaired successfully, your child will likely lead a normal life, often with no activity restrictions.
However, your child will need lifelong follow-up care with a cardiologist trained in congenital heart disease. Your cardiologist will likely recommend a follow-up exam once a year or more frequently if problems, such as a leaky heart valve, remain.
Your child might also need to take preventive antibiotics before certain dental and other surgical procedures if he or she:
- Has remaining heart defects after surgery
- Received an artificial heart valve
- Received artificial (prosthetic) material during heart repair
The antibiotics are used to prevent a bacterial infection of the lining of the heart (endocarditis).
Many people who have corrective surgery for atrioventricular canal defect don't need additional surgery. However, some complications, such as heart valve leaks, may require treatment.
Women who had an atrioventricular canal defect that was surgically corrected before any permanent lung damage occurred can generally expect to have normal pregnancies. However, pregnancy isn't recommended if serious heart or lung damage occurred before surgery.
Evaluation by a cardiologist is recommended for women with repaired or unrepaired atrioventricular canal defect before they attempt pregnancy.
Caring for a child with a congenital heart defect can be scary and challenging. To help make it easier:
- Seek support. Ask for help from family members and friends. Talk with your child's cardiologist about support groups and other types of assistance that are available near you.
- Record your baby's health history. Write down your child's diagnosis, medications, surgery and other procedures and the dates they were performed, the operative report from your child's surgeon, and any other important information about your child's care. This information will be useful for doctors who are unfamiliar with your baby. It will also help your child transition from pediatric to adult doctors.
- Talk about your concerns. Many children will have no limitations. But talk with the cardiologist about activities that are safe for your child. If some are off-limits, encourage your child in other pursuits rather than focusing on what he or she can't do.
Although every circumstance is different, remember that many children with congenital heart defects grow up to lead healthy lives.
Atrioventricular canal defect generally can't be prevented.
Heredity may play a role in some heart defects. If you have a family history of heart defects or if you already have a child with a congenital heart defect, talk with a genetic counselor and a cardiologist before getting pregnant again.
Immunization of children with rubella vaccine has been one of the most effective preventive strategies against congenital heart defects.
Aug. 14, 2015
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