Atrioventricular (AV) canal defect

Atrioventricular septal defect (AVSD), also known as atrioventricular canal defect, refers to a large hole in the center of the heart that prevents the separation of all four heart chambers and requires surgical repair.

The heart’s left side should pump blood out into the rest of the body, and the right side should send blood only to the lungs. In patients with AV septal defects, blood flows from the left to the right chambers and then into the lungs through the arteries. As a result, the heart and lungs work harder because of the extra blood going into the lungs, and lung congestion can occur because of high flow in those blood vessels.

This can lead to pulmonary hypertension into adulthood, as well as permanent lung damage. There also may be regurgitation (leaking) that can create heart failure symptoms.

AV septal defects often are associated with trisomy 21 (Down syndrome) or other genetic problems, though many patients will have normal chromosomes. Others may have additional heart problems. Patients with AV septal defect may have a hole between the heart’s upper chambers (atrial septal defect) without a hole separating the lower chambers (ventricular septal defect) and vice versa. They may also have abnormalities of the tricuspid and mitral valves.

Symptoms of AV septal defect in infants and children include:

• Poor weight gain
• Sweating during feeding
• Tachypnea (rapid and shallow breathing)
• Congestive heart failure symptoms

Though AV septal defects are diagnosed prenatally and in infancy, adults with unrepaired AV septal defects can experience symptoms, which include: 

• Heart murmurs due to valve leaks and blood flow across the hole
• Shortness of breath
• Decreased exercise capacity
• Palpitations

A cardiologist can evaluate your child for AV septal defect with noninvasive tests, such as:

• Electrocardiogram
• Echocardiograms
• Holter monitor
• Exercise stress tests
• Cardiac MRI

Sometimes, invasive tests are needed as well, including heart catheterization to determine whether the patient is a surgical candidate. 

Prior to surgical intervention, medical therapy may be employed to treat congestive heart failure symptoms and encourage infant weight gain. Patients with valve regurgitation will likely need heart failure medications to help their hearts pump better and/or lower their blood pressure. Patients with pulmonary hypertension may also require medications.

Surgery for AV septal defect is usually performed in infancy approximately 3-6 months of age. Once the defect has been repaired and healed, patients can usually return to normal activity without any particular precautions, and most children do very well after these repairs. Lifelong surveillance is required to assess the valve, the possible development of blockage in flow from the heart, and the development of heart rhythm (electrical) problems.

How well the repaired valves perform must be monitored long term. Some valves may need to be replaced with a mechanical one and occasionally can be repaired.