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What is atrioventricular canal defect?

Atrioventricular canal defect (AV 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 chambers need to be separated so oxygenated blood from the lungs doesn’t mix with unoxygenated blood from the rest of the body.

AV canal defect mixes the blood and prevents it from circulating to the correct place in the correct sequence. 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. The AV canal defect lets blood flow from the left to the right chambers and then into the lung 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 pressure in those blood vessels. This can lead to pulmonary hypertension into adulthood, as well as permanent damage. There also may be regurgitation (leaking) that can create heart failure symptoms.

AV canal defects often are associated with trisomy 21 (Down syndrome), though some patients may have normal chromosomes. Others may have additional heart problems. Adults with AV canal defect may have a hole between the heart’s upper chambers (atrial septal defect), a hole separating the lower chambers (ventricular septal defect) and/or abnormalities of the tricuspid and mitral valves.

Symptoms

Adult symptoms of an unrepaired AV canal defect may include:

  • Pulmonary hypertension
  • Shortness of breath
  • Palpitations
  • Problems with exercise
  • Heart murmurs due to valve leaks and blood flow across the hole

Symptoms in children include:

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

Diagnosis

A cardiologist can evaluate you with noninvasive tests such as:

  • Electrocardiogram
  • Holter monitor
  • Exercise stress tests
  • Echocardiograms
  • Heart catheterization (to determine whether the patient will have surgery)

Treatments

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 also may require medications.

Surgery on children usually is performed when an infant is approximately 3-6 months old, sometimes earlier, depending on the case. Lifelong surveillance is required due to related valve problems and possible development of left ventricular outflow obstruction.

How well the repaired valves perform must be monitored long term. Some valves later will need to be replaced with a mechanical one, because usually a valve can’t be further repaired. In other patients, further surgery can be used to patch leaks.

What to expect after treatment

Once the defect has been repaired and healed, patients usually can return to normal activity without any particular precautions necessary, without increasing their risk. Heart failure and pulmonary hypertension patients, though, may have some limitations placed on them.

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