Atrioventricular canal defect (patient information)

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 * Associate Editor(s)-In-Chief: Priyamvada Singh, M.B.B.S. [mailto:psingh@perfuse.org]; Assistant Editor(s)-In-Chief: Kristin Feeney, B.S. [mailto:kfeeney@perfuse.org]

Overview
The term atrioventricular canal defect refers to a collection of abnormalities in the heart's structure that are present at birth. An atrioventricular canal defect may be interchangeably called an endocardial cushion defect or atrioventricular septal defect. Regardless of name, this defect refers to the formation of a hole between the upper chambers of the heart (called atria). It also refers to problems involving the valves that work to maintain blood flow in the heart. Often, these valves overcircualte blood to the lungs causing the heart to be overworked and may even result in tissue enlargement of the heart muscle.

What are the symptoms of Atrioventricular canal defect?
Symptoms associated with an atrioventricular canal defect depend largely on the type of defect: partial or complete. A partial atrioventricular canal defect involves a malformation of the upper two chambers of the heart only. A complete atrioventricular canal defect is a malformation that allows blood to freely circulate amongst all four of the heart's chambers. In both partial and complete defects there is an increased, extra amount of blood that circulates to the lungs.

Complete atrioventricular canal defect: Signs/symptoms of a complete defect usually present within the first few weeks of life. Common symptoms include:
 * Poor appetite
 * Difficulty gaining weight
 * Blue discoloring of the skin (cyanosis)
 * Difficulty breathing/respiratory distress
 * Heart failure (signs include: wheezing, swelling of the legs, ankles, and feet, excessive sweating, sudden gaining of eight, irregular/fast heartbeat)

Partial atrioventricular canal defect: Signs/symptoms of a partial defect usually are asymptomatic (meaning without symptoms) until much later in life into adulthood. Common symptoms include:
 * An abnormal heart rhythm/heartbeat (arrhythmia)
 * Heart failure
 * High blood pressure, specifically within the lungs (pulmonary hypertension)

What causes atrioventricular canal defect?
The exact cause of an atrioventricular canal defect is unknown. There is some evidence to suggest a genetic component, especially in relation to Down syndrome as many Down syndrome patients have heart defects at birth.

Who is at highest risk?
Like most congenital heart defects, it is unclear exactly why certain babies are born with atrioventricular canal defects. There is evidence, however, to suggest that certain factors may increase the risk for a congenital heart defect. Risk factors include:
 * A family history of Down syndrome/chromosomal disorders
 * A family history of congenital heart defect
 * Expectant mothers who:
 * Contract German measles or other viral illnesses in the first trimester
 * Drink too much alcohol during pregnancy
 * Poorly manage diabetes during pregnancy
 * Take certain prescriptions during pregnancy, such as Accutane (a popular acne medicine noted for causing birth defects).

When to seek urgent medical care?
Contact your health care provider immediately if your child develops signs of heart failure, such as:
 * Decreased/poor appetite
 * Shortness of breath
 * Extreme fatigue/easy tiring
 * Swelling in the legs, ankles, or feet
 * A blue discoloration to the skin
 * Failure to thrive/gain weight

Diagnosis
A doctor may diagnose atrioventricular canal defects by:
 * Physical examination: During a physical examination, a defect may present if your baby has trouble breathing, difficult feeding, gaining weight, or if your doctor hears a heart murmur (a heart sound associated with abnormal circulation of blood)
 * Echocardiogram: This kind of non-invasive, painless sonar test can help the doctor closely examine an atrial septal defect. It uses sound waves to produce an image of the ventricles, atrium and great vessels. An echocardiogram can determine if blood is flowing properly from the right to the left systems. Furthermore, the doctor can measure the speed of blood flow through patient's heart and the pulmonary blood pressure using the echocardiogram. This is important to determine if there is excess flow through the lungs and if there is damage to the vessels in the lung.
 * Cardiac catheterization: An invasive procedure in which a small, thin flexible tube is placed into an artery or a vein in the groin and threaded up into the heart. A dye is injected to provide contrast to make heart anatomy visible during imaging. The catheter gives the doctor the ability to measure pressure in the heart chambers and in the blood vessels.

Treatment options
Surgery is the most appropriate course of treatment to fix both, complete and partial atrioventricular canal defects. The surgerical procedure will focus using one or two patches to close the hole in the septum. As the heart heals, the lining of the heart will grow over the patch and permanently close the septum.

In partial atrioventricular canal defects, surgery focuses less on patching and more on the repair of the mitral valve. This repair will allow the valve to close tightly and prevent disruptions in blood circulation, which cause overworking of the heart and ultimate enlargement of the heart muscle tissue. Complete atrioventricular canal defects, the surgery will involve repair of a single valve into two valves, where one will be on the left side and one will be on the right side of the patched septum. If reconstruction and repair is not possible during partial or complete defect surgery, an entire valve replacement may be necessary.

Where to find medical care for Atrioventricular canal defect?
Directions to Hospitals Treating Atrioventricular canal defect

What to expect (Outlook/Prognosis)?
After a successful surgery, the prognosis is good. Children are likely to lead a normal, healthy life without activity restrictions. Care, however, is lifelong and requires yearly follow-ups to track progress and monitor potential complications, such as a leaky heart valve.

Children will also have to take preventative antibiotics prior to any procedures, dental or surgical. These preventative antibiotics help minimize the potential risk of complications such as endocarditis, a bacterial infection occurring within the lining of the heart that can be very severe and life-threatening. Endocarditis is more common:
 * When the child may have lingering defects post-surgery.
 * After surgery with an artificial valve repair.
 * After surgical patching utilizing artificial materials.

Often, adults may not need any additional surgery. Women anticipating childbearing must have an atrioventricular canal defect evaluated by a cardiologist prior to pregnancy.

Prevention
There is no known way to prevent the defect, but some of the complications can be prevented with early detection.