Atrioventricular Septal Defect

Atrioventricular septal defect is a congenital heart defect, meaning it is present at birth. It involves a combination of structural problems affecting the center of the heart. Children born with this condition have a hole in the wall that separates the heart chambers, along with abnormalities of the heart valves that regulate blood flow.

Because of this defect, extra blood flows to the lungs. The increased blood flow forces the heart to work harder than normal, which can cause the heart muscle to enlarge over time. If left untreated, atrioventricular septal defect may lead to heart failure and high blood pressure in the lungs. Treatment most often involves surgery during the first year of life to close the hole and repair the affected valves.

This condition is also known as atrioventricular canal defect or endocardial cushion defect.

Symptoms

Atrioventricular septal defect may involve only the two upper chambers of the heart or all four chambers. In both forms, excess blood flows into the lungs. Symptoms depend on whether the defect is partial or complete.

In a complete defect, all four chambers of the heart are involved. Symptoms usually appear within the first weeks of life and often resemble signs of heart failure. These may include:

• Blue or gray skin color due to low oxygen levels

• Difficulty breathing or rapid breathing

• Excessive sweating

• Fatigue

• Rapid or irregular heartbeat

• Poor appetite

• Poor weight gain

• Swelling of the legs, ankles or feet

• Wheezing

In a partial defect, only the two upper chambers of the heart are affected. Symptoms may not appear until adolescence or adulthood and are often related to complications such as valve problems, pulmonary hypertension or heart failure. Symptoms may include:

• Fatigue and weakness

• Nausea and loss of appetite

• Persistent cough or wheezing

• Rapid or irregular heartbeat

• Reduced ability to exercise

• Shortness of breath

• Swelling of the legs, ankles or feet

• Chest pressure or pain

Causes

Atrioventricular septal defect develops before birth while the baby’s heart is forming. The exact cause is not clearly known. Genetic factors appear to play a role, and the condition is commonly associated with Down syndrome.

In a normally developing heart, four chambers and separate valves form to ensure blood flows in the correct direction. In atrioventricular septal defect, the walls between the chambers and the valves do not form properly. This allows blood to mix between chambers and flow abnormally through the heart, increasing strain on the heart and lungs.

Risk factors

Several factors may increase the risk of atrioventricular septal defect, including:

• Genetic conditions, especially Down syndrome

• A family history of congenital heart disease

• Rubella infection during pregnancy

• Poorly controlled diabetes during pregnancy

• Alcohol use during pregnancy

• Smoking during pregnancy

• Use of certain medications during pregnancy that affect fetal development

Complications

If untreated, atrioventricular septal defect can lead to serious complications. These may include:

• Enlargement of the heart due to increased workload

• High blood pressure in the lungs, known as pulmonary hypertension

• Recurrent respiratory tract infections

• Heart failure caused by the heart’s inability to pump enough blood

Although treatment greatly improves outcomes, complications can still occur later in life. These may include breathing problems from lung damage, irregular heart rhythms, leaky heart valves, and narrowing of the heart valves.

Pregnancy may be possible for individuals who had corrective surgery before permanent lung damage developed. Pregnancy is generally not recommended for those with severe heart or lung complications. Consultation with a cardiologist experienced in congenital heart disease is important before planning a pregnancy.

Prevention

There is no known way to prevent atrioventricular septal defect. Some congenital heart defects are inherited. People with a personal or family history of congenital heart disease may benefit from genetic counseling and cardiology evaluation before becoming pregnant.