What Is an Atrioventricular Canal Defect?

The term "atrioventricular canal defect" refers to specific and profound malformations of the heart that occur before birth. In its classic form, this set of defects involves communications or holes between the right and left sides of the heart, in addition to mild to major deformations of the tricuspid and mitral valves. Symptoms of heart failure from this condition tend to appear within the first few months of life. Early surgery often fully repairs these defects and gives children normal and healthy lives.

Ordinarily, a wall called the septum, which prevents blood from communicating between the right and left-sided chambers, divides the two sides of the heart. When an atrioventricular canal defect is present, the septum has not formed properly and large septal holes between the atria and the ventricles allow blood to move from side to side. Moreover, the valves controlling blood between each atrium and ventricle, the tricuspid and mitral valves, usually do not work properly, either. The result is greater blood flow to the lungs, which may permanently damage them, and poor oxygenation of the body’s tissues.

There is a variant of this condition called partial atrioventricular canal defect. In this presentation, only the atria, which are the top two heart chambers, and possibly the mitral and tricuspid valve are affected. Sometimes this condition is so mild that it isn’t detected until late childhood or early adulthood. Other times, unusual heart sounds or failing health on the part of the child brings this condition to light earlier.

With classic atrioventricular canal defect, a number of symptoms tend to present in early life. A baby may have trouble eating, and be slow to gain weight. Rapid breathing could be accompanied by cyanosis, where fingers, toes and skin have a bluish or pale color. A doctor is likely to note that the baby has an unmistakable heart murmur. Additional symptoms could include fluid retention and heavy perspiration.

The next step in diagnosing atrioventricular canal defect is to refer the patient to a pediatric cardiologist. These specialists examine the child and may order several additional tests. Among them are a pediatric echocardiogram, which is essentially a sonogram of the baby’s heart. X-rays, computerized tomography, and catheterization could also be advised. These tests help visualize the heart, make a correct diagnosis, and determine what repairs are possible.

Ideally, surgery for atrioventricular canal defect takes place soon after diagnosis. The precise repair may vary with presentation of the defect, degree of mitral and tricuspid valve involvement, and any possible damage to the lungs. Generally, the repair takes place immediately to prevent lung damage, but sometimes this is not possible. When lung damage is severe, a total repair isn’t always feasible. In most other cases, surgeons can fully patch any holes, repair or replace the valves, and restore full function to the heart.

A child with early surgical intervention may face an uncomplicated course. As kids age, they might require minor repairs of leaky valves, and all of them will need to take antibiotics prior to dental procedures to prevent bacterial endocarditis. In most other ways, a child with atrioventricular canal defect has a good chance of living a normal life.