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. 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
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 (dyspnea) 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
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.
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.
- Mayo clinic