Atrioventricular Septal Defect: What You Need to Know

What Is an Atrioventricular Septal Defect?

An atrioventricular septal defect is a structural heart problem present at birth. It is also called an atrioventricular canal defect, AV canal defect, or endocardial cushion defect.

A healthy heart has four chambers. The right and left atria are the two upper chambers, while the right and left ventricles are the two lower chambers. Walls called septa separate the right side from the left, and valves keep blood moving in the correct direction.

In AVSD, the tissue near the center of the heart does not develop normally. This may leave openings between the chambers and create abnormalities in the mitral and tricuspid valves. Instead of traveling neatly along separate routes, oxygen-rich and oxygen-poor blood may mix. Extra blood can then move toward the lungs, forcing the heart and pulmonary blood vessels to handle more work than intended.

The CDC estimates that approximately 1 in 1,587 babies in the United States is born with AVSD. That works out to more than 2,000 affected babies in an average year.

Types of Atrioventricular Septal Defect

AVSD is a spectrum rather than a one-size-fits-all diagnosis. The child’s cardiologist will describe the anatomy in detail because the exact structures involved determine the timing and type of treatment.

Complete AVSD

Complete atrioventricular septal defect is the most extensive form. There is a large central opening where the walls between the atria and ventricles should meet. Instead of having separate mitral and tricuspid valves, the heart has one common atrioventricular valve.

Blood can pass between all four chambers, and the common valve may leak. This sends excessive blood toward the lungs and can lead to symptoms of heart failure during early infancy. The phrase “heart failure” sounds terrifying, but in babies it usually means the heart is struggling to keep up with increased workloadnot that it has suddenly stopped working.

Partial or Incomplete AVSD

Partial AVSD typically includes an opening between the upper chambers, usually a primum atrial septal defect, along with an abnormality of the left atrioventricular valve. The valve may have a cleft or split that allows blood to leak backward.

Because there may be no large opening between the ventricles, symptoms can be milder and appear later. Some children are diagnosed after a doctor hears a heart murmur during an otherwise routine visit.

Transitional AVSD

A transitional defect lies between the partial and complete forms. It may include an opening between the atria, one or more small openings between the ventricles, and abnormalities of the atrioventricular valves.

Balanced and Unbalanced AVSD

Doctors may also describe an AVSD as balanced or unbalanced. In a balanced AVSD, the common valve directs blood relatively evenly into both ventricles. In an unbalanced defect, one ventricle receives much more blood and may grow larger while the other remains underdeveloped.

Unbalanced AVSD can require a more complex treatment strategy. Some children may be candidates for repair using both ventricles, while others need staged procedures designed for single-ventricle circulation.

What Causes AVSD?

AVSD develops during the earliest stages of pregnancy as the fetal heart is forming. In most cases, no single action, food, event, or parental decision can be identified as the cause. Parents did not create the defect by lifting something heavy, missing a prenatal vitamin, or having one stressful Tuesday.

Researchers believe that a combination of genetic and environmental factors may affect heart development. AVSD has a particularly strong association with Down syndrome, also known as trisomy 21. However, many babies with AVSD do not have Down syndrome, and most babies with Down syndrome do not have this specific defect.

AVSD can also occur with heterotaxy syndrome, other chromosome differences, or additional congenital heart abnormalities. When appropriate, a care team may recommend genetic counseling and testing to clarify whether the heart defect is part of a broader condition.

Factors associated with a higher overall risk of congenital heart defects include poorly controlled diabetes during pregnancy, smoking, alcohol exposure, rubella infection, and certain medications. An association does not mean that one factor definitely caused an individual child’s AVSD.

Symptoms and Warning Signs

The symptoms depend on whether the defect is complete or partial, how much blood flows through the openings, how severely the valve leaks, and whether other heart conditions are present.

Symptoms in Babies With Complete AVSD

Babies with complete AVSD may initially appear stable. During the first several weeks of life, however, resistance in the lung blood vessels naturally falls. More blood then crosses the defect and travels toward the lungs, making symptoms more noticeable.

• Fast or labored breathing
• Sweating, especially during feeding
• Tiring before finishing a bottle or nursing session
• Slow weight gain or poor growth
• Frequent respiratory infections
• Pale, cool, or clammy skin
• Rapid heartbeat
• Swelling in more advanced cases

Symptoms in Partial AVSD

A child with partial AVSD may have few obvious symptoms during infancy. As the years pass, a significant opening or leaky valve can cause fatigue, shortness of breath during activity, reduced exercise tolerance, an irregular heartbeat, or recurrent respiratory infections.

Severe breathing difficulty, blue or gray lips, extreme sleepiness, fainting, or an inability to feed requires urgent medical evaluation. Parents should follow the emergency instructions provided by their child’s cardiac team rather than trying to perform an internet diagnosis at 2 a.m.the internet has many talents, but listening to a baby’s heart is not one of them.

How AVSD Is Diagnosed

Prenatal Ultrasound and Fetal Echocardiography

Some atrioventricular septal defects are identified during a routine prenatal ultrasound. When a heart abnormality is suspected, a fetal echocardiogram provides detailed images of the baby’s heart structure, valves, rhythm, and blood flow.

A prenatal diagnosis gives families time to meet pediatric cardiologists, discuss genetic testing, choose an appropriate delivery hospital, and learn what care may be needed after birth. It does not always mean that an emergency procedure will be required immediately after delivery.

Physical Examination

After birth, a clinician may hear a heart murmur or notice fast breathing, slow growth, or other signs of increased blood flow to the lungs. A murmur is a sound created by turbulent blood flow. It is a clue, not a complete diagnosis.

Echocardiogram

An echocardiogram uses sound waves to create moving pictures of the heart. It is the primary test for confirming AVSD and showing the size of the openings, valve anatomy, valve leakage, ventricular balance, heart function, and blood-flow pattern.

Additional Tests

An electrocardiogram can reveal heart rhythm patterns and signs of chamber strain. A chest X-ray may show an enlarged heart or increased blood flow in the lungs. Pulse oximetry measures oxygen saturation. Cardiac MRI, CT imaging, or cardiac catheterization may be used when additional anatomical or pressure information is needed.

Treatment Before Surgery

Medicine cannot close an AVSD, but it can help control symptoms while a baby grows and the surgical team prepares for repair.

Diuretics may help the body remove excess fluid and reduce congestion in the lungs. Other heart medications may be prescribed based on the child’s symptoms and ventricular function. Families should give every dose exactly as directed and contact the care team before changing or stopping medication.

Nutrition is another major part of treatment. Feeding can feel like a workout for a baby with congenital heart disease. A child may need fortified breast milk, higher-calorie formula, smaller and more frequent feedings, or temporary support through a feeding tube. These strategies conserve energy and promote growth before surgery.

Surgery for Atrioventricular Septal Defect

Surgery is the definitive treatment for both complete and clinically significant partial AVSD. The exact schedule is individualized according to symptoms, valve leakage, lung pressure, weight gain, associated conditions, and the anatomy seen on imaging.

Complete AVSD is generally repaired during early infancy, often within the first several months of life. Earlier surgery may be necessary when symptoms are difficult to control or pulmonary pressure is rising. Partial AVSD may be repaired later when the child is stable, although important valve leakage or other concerns can move the operation forward.

What Happens During the Operation?

The operation is performed through an incision in the chest with support from a heart-lung machine. The surgeon closes the septal openings using one or two patches. The common atrioventricular valve is then divided or reconstructed to create effective right- and left-sided valves.

The goal is not merely to plug a hole. The surgeon must also produce valves that close well without becoming too narrow and preserve unobstructed blood flow through the heart. Every AVSD has its own anatomical personality, and some are considerably more opinionated than others.

Hospital Recovery

After surgery, the child typically spends time in a cardiac intensive care unit. Breathing support, drainage tubes, intravenous medicines, temporary pacing wires, and multiple monitors are common. They can look alarming, but each has a specific job.

As recovery progresses, breathing support and medications are reduced. Feeding resumes gradually, and the medical team watches closely for rhythm problems, infection, fluid buildup, valve leakage, and changes in heart function. The length of hospitalization varies widely.

Possible Complications and Long-Term Follow-Up

Most children do well after AVSD repair, but surgery creates a repaired heart rather than a heart that never had a congenital defect. Regular follow-up with a pediatric cardiologistand later an adult congenital heart disease specialistis important.

Potential long-term concerns include:

• Leakage of the left atrioventricular valve
• Narrowing of an atrioventricular valve
• A small residual opening near a surgical patch
• Narrowing of the path from the left ventricle to the aorta
• Abnormal heart rhythms
• Heart block requiring a pacemaker
• Pulmonary hypertension
• Reduced heart-pumping function

Some patients eventually need another catheter procedure or operation, most commonly to address valve leakage or narrowing. This possibility does not mean the original repair failed. A child’s heart grows, repaired tissue changes, and valves that worked well in infancy may require attention years later.

Follow-up may include echocardiograms, electrocardiograms, ambulatory rhythm monitoring, exercise testing, or cardiac MRI. Patients should not disappear from cardiology care simply because they feel well.

Life After AVSD Repair

Many children with a successfully repaired atrioventricular septal defect attend school, play with friends, travel, and participate in age-appropriate physical activities. Restrictions depend on residual valve problems, heart function, pulmonary pressure, rhythm issues, and other diagnoses.

Routine dental care matters because healthy teeth and gums reduce the chance that bacteria will enter the bloodstream. Antibiotics before certain dental procedures are recommended only for specific high-risk situations, so families should follow their cardiologist’s individualized advice rather than assuming they are always necessary.

As teenagers become more independent, they should gradually learn the name of their heart condition, what surgery they had, which medicines they take, and when to seek care. Adults with repaired AVSD should receive guidance about exercise, employment, contraception, pregnancy, and genetic counseling from clinicians experienced in adult congenital heart disease.

Questions to Ask the Cardiology Team

• Is the AVSD complete, partial, transitional, balanced, or unbalanced?
• How much are the atrioventricular valves leaking?
• Is the pressure in the lung arteries elevated?
• What symptoms should prompt an urgent call or emergency visit?
• Does my child need medication or higher-calorie nutrition?
• When is surgery likely to be recommended?
• What type of repair does the surgeon expect to perform?
• What are the center’s typical outcomes for this anatomy?
• How often will echocardiograms and follow-up visits be needed?
• Should our family meet with a genetic counselor?

The Family Experience: What the AVSD Journey May Feel Like

No two families experience atrioventricular septal defect in exactly the same way. Still, certain moments are familiar to many parents: the shock of hearing the diagnosis, the strange new vocabulary, feeding challenges, the wait for surgery, and the mixture of relief and nervousness that follows discharge.

Learning the Diagnosis

A prenatal or newborn diagnosis can turn an ordinary day into a blur of diagrams, acronyms, and appointments. Parents may hear “complete AV canal,” “valve regurgitation,” and “pulmonary overcirculation” before they have figured out where to park at the hospital. Writing questions in a phone or notebook helps because even the most organized brain can become surprisingly slippery during a stressful consultation.

Many families find it useful to ask the cardiologist to draw the defect and explain it twice: once in medical terms and once in everyday language. Requesting clarification is not being difficult. It is participating in the child’s care.

Managing Feeding at Home

Feeding is often the first daily challenge. A baby may begin eagerly, then breathe faster, sweat, or fall asleep after taking only part of the expected amount. Parents sometimes feel as though every ounce has become a final exam.

A written feeding plan can reduce uncertainty. Families may track intake, wet diapers, weight, breathing, and medication doses. The goal is not to produce a museum-quality spreadsheet. It is to notice meaningful changes and give the clinical team useful information.

Parents should report worsening breathing, repeated vomiting, fewer wet diapers, major declines in intake, or poor weight gain. Needing fortified milk or a feeding tube is not a parental failure. It is medical support for a baby whose heart is using extra energy.

Preparing for Surgery

The weeks before surgery may feel both too long and too short. Parents often want the repair completed while simultaneously wishing they could postpone the day forever. Both reactions are normal.

Practical preparation can restore a sense of control. Families can arrange care for siblings, confirm insurance details, prepare transportation, pack comfortable clothing, and identify one person who will update relatives. That last step can prevent parents from sending the same emotionally exhausting text message 37 times.

Before the operation, families should understand the planned repair, the expected intensive-care course, pain management, feeding goals, visiting rules, and the complications the team will monitor.

Seeing the Child After Surgery

The first visit to the cardiac intensive care unit can be emotionally intense. Swelling, tubes, dressings, monitors, and ventilator equipment may make the child look unfamiliar. Asking a nurse to explain each line and machine can make the scene less frightening.

Recovery rarely follows a perfectly straight line. A baby may have an excellent morning and a difficult evening. Feeding can improve slowly. Oxygen or medication may be reduced and then briefly restarted. These changes do not automatically mean that something has gone seriously wrong.

Going Home and Moving Forward

Discharge is exciting, but it may also remove the comforting wall of hospital monitors. Parents frequently check breathing, skin color, temperature, and the surgical incision more often than necessary during the first nights at home.

A clear discharge plan should cover medications, wound care, lifting precautions, feeding, bathing, pain control, warning signs, and follow-up appointments. Keeping the cardiology number in an easy-to-find place is more useful than relying on memory during a stressful moment.

Over time, many families notice that heart care becomes part of life rather than the center of every day. Appointments remain important, but so do first words, messy birthday cake, playground negotiations, school projects, and all the ordinary childhood chaos that once seemed impossibly far away.

Conclusion

Atrioventricular septal defect is a complex congenital heart condition involving openings between the heart chambers and abnormalities of the atrioventricular valves. Complete AVSD often causes symptoms during early infancy and generally requires surgical repair within the first several months of life. Partial defects may be quieter but still need careful evaluation and treatment.

Early diagnosis, symptom management, nutritional support, skilled surgery, and lifelong congenital cardiology care give many children the opportunity to grow into active adults. The path may include intimidating terminology and uncertain days, but families do not have to travel it alone. A specialized heart team can explain the anatomy, personalize the treatment plan, and help transform a frightening diagnosis into a manageable medical journey.

Note: This article provides general educational information and is not a substitute for diagnosis or treatment from a pediatric cardiologist or other qualified healthcare professional. Contact the child’s medical team promptly about new, severe, or worsening symptoms.