Atrioventricular canal defect

Overview

Atrioventricular canal defect is a mix of problems affecting the center of the heart. The heart condition is present at birth. That means it's a congenital heart defect. Children born with this condition have a hole in the wall between the heart's chambers. They also have problems with the valves that control blood flow in the heart.

Atrioventricular canal defect allows extra blood to flow to the lungs. The extra blood forces the heart to work too hard, causing the heart muscle to grow larger.

Untreated, atrioventricular canal defect can cause heart failure and high blood pressure in the lungs. Treatment usually involves surgery during the first year of life to close the hole in the heart and to repair the valves.

Other names for this condition are:

• Atrioventricular septal defect (AVSD)
• Endocardial cushion defect

Symptoms

Atrioventricular canal defect can involve only the two upper chambers of the heart or all four chambers. In both types, extra blood flows into the lungs. Symptoms depend on whether the defect is partial or complete.

Complete defect

The condition affects all of the heart's chambers. Symptoms of a complete atrioventricular canal defect usually develop in the first weeks of life. Symptoms are generally similar to those of heart failure. They may include:

• Blue or gray skin color due to low oxygen levels
• Difficulty breathing or rapid breathing
• Excessive sweating
• Fatigue
• Irregular or rapid heartbeat
• Lack of appetite
• Poor weight gain
• Swelling in the legs, ankles and feet
• Wheezing

Partial defect

The condition affects only the two upper heart chambers. Symptoms of a partial atrioventricular canal defect may not appear until early adulthood. The symptoms may be due to complications such as heart valve problems, high blood pressure in the lungs or heart failure. Symptoms may include:

• Fatigue and weakness
• Nausea and lack of appetite
• Persistent cough or wheezing
• Rapid or irregular heartbeat, also called an arrhythmia
• Reduced ability to exercise
• Shortness of breath
• Swelling in the legs, ankles and feet
• Chest pressure or pain

Causes

Atrioventricular canal defect occurs before birth when a baby's heart is developing. Experts aren't sure of the cause. Having Down syndrome might increase the risk.

How the heart works

To understand congenital heart defects, it may be helpful to know how the heart typically works.

The heart is divided into chambers. The two upper chambers are called the atria. The two lower chambers are called the ventricles.

The right side of the heart moves blood into vessels that lead to the lungs, where the blood receives oxygen. The oxygen-rich blood flows back to the heart's left side and into the body's main artery, called the aorta. From there, the blood flows to the rest of the body.

Valves control blood flow into and out of the heart chambers. These heart valves open to let blood in and close to keep blood from flowing backward.

What happens in atrioventricular canal defect

In a partial atrioventricular canal defect:

• There's a hole in the heart's wall between the upper chambers.
• There are also changes in the tricuspid and mitral valves.
• The changes prevent the valves from closing all the way.
• Blood can move the wrong way through the irregular valve opening.
• The mitral valve between the upper and lower left chambers is most often affected.

In a complete atrioventricular canal defect:

• There's a large hole in the center of the heart. The hole is where the walls between the upper and the lower chambers meet.
• Oxygen-rich and oxygen-poor blood mix through the hole.
• There's one large valve between the heart's upper and lower chambers, instead of separate ones.
• Blood leaks through the one large valve into the lower heart chambers.
• The heart must work harder to pump blood. The heart becomes larger.

Risk factors

Things that might increase the risk of atrioventricular canal defect include:

• Genetics. Congenital heart disease appears to run in families. It's associated with many genetic syndromes. For instance, children with Down syndrome often have heart problems present at birth.
• German measles, also called rubella. Having rubella during pregnancy may affect how the baby's heart develops while in the womb.
• Diabetes. Poorly controlled diabetes during pregnancy may affect a baby's heart development. Gestational diabetes generally doesn't increase the risk of congenital heart disease.
• Alcohol use. Drinking alcohol while pregnant has been linked to an increased risk of heart defects in the baby.
• Smoking. If you smoke, quit. Smoking during pregnancy increases the risk of congenital heart defects in the baby.
• Some medicines. Taking certain medications while pregnant may cause heart problems and other birth defects in the baby. Always tell your health care provider about the medications you take.

Complications

Possible complications of atrioventricular canal defect include:

• Enlargement of the heart. Increased blood flow through the heart forces it to work harder than normal, causing it to become larger.
• High blood pressure in the lungs. This condition is also called pulmonary hypertension. A hole in the heart lets oxygen-rich blood mix with oxygen-poor blood. The lungs get too much blood. Pressure builds up in the lungs.
• Respiratory tract infections. A hole in the heart can lead to repeated lung infections.
• Heart failure. If atrioventricular canal defect is not treated, the heart can't pump enough blood to meet the body's needs.

Treatment greatly improves the outlook for children with atrioventricular canal defect. But complications may still occur later in life. They may include:

• Breathing problems due to lung damage
• Irregular heart rhythms
• Leaky heart valves, also called valve regurgitation
• Narrowing of the heart valves

Pregnancy

Those who had atrioventricular canal defect surgery before permanent lung damage occurred are often able to have a successful pregnancy. Pregnancy is not recommended if you had serious heart or lung damage before atrioventricular canal defect surgery.

Before becoming pregnant, talk to a heart doctor trained in congenital heart disease about the possible risks and complications. This type of care provider is called an adult congenital cardiologist. Together you can discuss and plan for any special care needed during pregnancy.