Children's Heart Institute
Atrioventricular (AV) Canal Defects
Atrioventricular (AV) Canal defects are complicated defects of the heart. The right side of the heart collects unoxygenated blood from the body in a thin-walled chamber called the right atrium. The blood then goes through a valve (which keeps blood flowing in one direction) into the main pumping chamber, called the right ventricle. Similarly, when oxygenated blood returns from the lungs to the heart it collects in the left atrium and goes through a valve into the left ventricle. The left ventricle pumps the oxygenated blood to the body.
Usually, there is a wall between the two atria, called the atrial septum, and between the two ventricles, called the ventricular septum. The two valves which separate the two atria from the two ventricles are adjacent to each other. There is a point in the middle of the heart where the atrial septum, the two valves, and the ventricular septum come together. In children with AV Canal defects, it is this point which is not formed properly.
The most common form of AV Canal defects is the complete form, where a large portion of atrial septum and ventricular septum are missing. In addition, the two valves which are adjacent to each other are connected, leaving one opening between all four chambers. It is possible to have "incomplete" defects where only some of the area is properly formed and some is deficient. A large number of patients with Down's syndrome have AV Canal defects, although a number of children without Down's will develop an AV Canal defect.
Children with AV Canal defects have a large hole between the left side and right side of their hearts. Since the resistance of flow to the lungs is less than the resistance of flow to the body, blood in the heart tends to cross over from the left (body) side of the heart to the right (lung) side. Before surgery, children may have much too much blood flow to their lungs. This may cause problems with breathing and weight gain. The timing of surgery often depends on how much of a problem the extra blood flow is causing the child.
Surgery for AV Canal defects is usually performed at 3-8 months of age. Surgery involves a vertical incision in the middle of the chest. It is necessary to place the child on the heart-lung machine. During surgery, a patch is placed which separates the two atria and two ventricles from each other, and also divides the two valves.
Most children do very well after surgery for AV Canal defects. However, it is recognized that the surgery is complex and a small percentage of children after AV Canal surgery will have problems, usually with the left-sided valve (the valve between the left atrium and left ventricle). Despite the repair, the valve is not truly normal and is prone to leaking. Approximately 10% of children who have a repair of an AV Canal can expect to need further surgery at some time in their lives, usually to further repair the left-sided heart valve.
Pediatric Cardiology ClinicUniversity of Texas Health Science Center Professional Building
6410 Fannin, Suite 500
Houston, TX 77030
Phone: (832) 325-6516
Pediatric Cardiovascular Surgery ClinicUniversity of Texas Health Science Center Professional Building6410 Fannin, Suite 950Houston, TX 77030
Phone: (713) 500-7339
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