Your baby was just diagnosed with Down syndrome. The pediatric cardiologist mentioned a heart defect. You're sitting in a hospital room trying to decode terms like AVSD, septal defect, and surgical repair while processing a diagnosis you didn't expect.

Approximately 50% of infants with Down syndrome have a congenital heart defect. That statistic doesn't tell you what you need to know right now: which defects are most common, whether surgery is inevitable, what the procedure involves, or what survival outcomes look like in 2026.

Here's what you need to understand about the three most common heart defects in Down syndrome, how they're diagnosed, what the surgical timeline looks like, and what modern outcomes mean for your child's long-term health.

The Most Common Heart Defects in Down Syndrome

Three defects account for the majority of congenital heart disease in children with Down syndrome: atrioventricular septal defect (AVSD), ventricular septal defect (VSD), and atrial septal defect (ASD).

Atrioventricular septal defect (AVSD) is the most common. It's a hole in the center of the heart where the upper chambers (atria) and lower chambers (ventricles) meet. In a typical heart, these chambers are separated by tissue. In AVSD, that separation didn't form completely during fetal development. Blood flows between chambers that should remain separate, forcing the heart to work harder and allowing oxygen-rich and oxygen-poor blood to mix.

AVSD occurs in approximately 40–45% of children with Down syndrome who have heart defects. The condition is sometimes called endocardial cushion defect or AV canal defect, different names for the same structural problem.

Ventricular septal defect (VSD) is a hole between the two lower chambers. Blood flows from the left ventricle (which pumps oxygen-rich blood to the body) back into the right ventricle (which pumps blood to the lungs). Small VSDs may close on their own. Larger ones require surgical repair.

Atrial septal defect (ASD) is a hole between the two upper chambers. Blood flows from the left atrium to the right atrium, increasing the volume of blood the right side of the heart must pump to the lungs. Like VSDs, small ASDs sometimes close without intervention. Larger defects need repair.

Your pediatric cardiologist will explain which defect your child has, how large it is, and whether it's isolated or part of a more complex structural issue. These distinctions matter for surgical planning.

How Heart Defects Are Diagnosed

Most heart defects in infants with Down syndrome are detected through routine screening, not because the baby shows obvious symptoms.

An echocardiogram is the standard diagnostic tool. It's an ultrasound of the heart that shows chamber size, valve function, and blood flow patterns. The test is noninvasive, doesn't hurt, and takes 30–60 minutes. A pediatric cardiologist reviews the images and determines whether a defect is present, what type it is, and how it's affecting your baby's heart function.

The American Academy of Pediatrics recommends that all infants with Down syndrome receive an echocardiogram within the first month of life, even if they appear healthy. Some heart defects cause no symptoms in newborns but can lead to complications if left untreated.

You may hear the term "cardiac catheterization" mentioned. This is a separate procedure used when the echocardiogram suggests a complex defect or when the cardiologist needs more detailed measurements before surgery. A thin tube (catheter) is inserted through a blood vessel and guided to the heart. It's more invasive than an echo but provides information that imaging alone can't capture.

When Surgery Happens

Not every heart defect requires immediate surgery. The timing depends on the type of defect, its size, and how it's affecting your baby's ability to gain weight and maintain oxygen levels.

For AVSD, surgery typically happens between 3 and 6 months of age. Waiting too long allows the increased blood flow to the lungs to cause permanent damage to the blood vessels. Operating too early increases surgical risk in a very small infant. The window exists because most babies are large enough by 3 months to tolerate the procedure, but the defect hasn't yet caused irreversible lung damage.

VSD repair timing varies. Small defects that aren't causing symptoms may be monitored for the first year to see if they close on their own. Larger VSDs that lead to poor weight gain, rapid breathing, or frequent respiratory infections are repaired earlier, often between 3 and 6 months.

ASD repair is usually delayed. Most ASDs are repaired between 2 and 4 years of age unless symptoms develop earlier. The defect rarely causes problems in infancy, and delaying surgery allows the child to grow larger, which reduces surgical risk.

Your cardiologist will explain the specific timeline for your child. These are general patterns, not rigid rules.

What the Surgery Involves

Open-heart surgery to repair a septal defect involves opening the chest, stopping the heart temporarily, and routing blood through a heart-lung bypass machine while the surgeon closes the hole.

For AVSD repair, the surgeon reconstructs the center of the heart using a patch (usually made from the pericardium, the sac around the heart) and repairs the valves between the chambers. The goal is to separate the upper and lower chambers completely and restore normal blood flow.

VSD and ASD repairs are simpler. The surgeon closes the hole with a patch or, in some cases, with stitches alone if the defect is small.

The surgery takes 3–6 hours depending on complexity. Your child will spend 1–3 days in the pediatric intensive care unit (PICU) afterward, then move to a regular hospital room for another 3–5 days before going home.

Recovery at home takes 4–6 weeks. You'll be instructed to avoid activities that put pressure on the chest (no rough handling, no lifting the baby under the arms) and to watch for signs of infection at the incision site. Your child will need follow-up echocardiograms to ensure the repair is holding and the heart is functioning normally.

Survival Outcomes and Long-Term Outlook

Surgical outcomes for congenital heart defects in children with Down syndrome have improved dramatically over the past three decades.

In the 1980s, survival rates for AVSD repair in children with Down syndrome were approximately 70–80%. Today, survival rates exceed 95% at experienced pediatric cardiac surgery centers. Improvements in surgical technique, anesthesia, and post-operative care account for the difference.

Most children who undergo successful repair live normal lifespans with no restrictions on physical activity. Some will need lifelong cardiology follow-up to monitor for valve problems or arrhythmias, but these complications are manageable.

The presence of a repaired heart defect does not preclude participation in sports, school activities, or independent living. Your child's cardiologist will provide specific guidance based on the type of defect and the quality of the repair, but the default assumption is full participation unless a specific contraindication exists.

Questions to Ask Your Pediatric Cardiologist

You're entitled to clear answers. These questions help you understand your child's specific situation:

• What type of defect does my child have, and how large is it?
• Is this an isolated defect or part of a more complex structural problem?
• What's the timeline for surgery, and what determines that timing?
• What are the risks specific to my child's age and overall health?
• What will recovery look like, both in the hospital and at home?
• What follow-up care will my child need after surgery?
• Are there any activity restrictions after recovery?

Your cardiologist should be able to answer each of these in language you can understand. If the explanation doesn't make sense, ask again. You're making decisions about your child's care based on this information.

What Happens If Surgery Isn't Recommended

Not every heart defect requires surgical repair. Small VSDs and ASDs sometimes close on their own or remain small enough that they don't interfere with heart function.

Your cardiologist will monitor the defect with periodic echocardiograms, typically every 6–12 months during infancy, then less frequently as your child grows. If the defect closes or remains stable, no further intervention is needed.

If symptoms develop later (poor growth, fatigue during physical activity, frequent respiratory infections), surgery may be recommended at that point. The decision to wait is based on evidence that the defect isn't causing harm and that delaying surgery reduces risk without increasing the chance of complications.

What You Need to Know Right Now

Your baby's Down syndrome diagnosis came with a cardiac screening recommendation for a reason. Heart defects are common in this population, but they're also well understood and highly treatable.

If the echocardiogram shows a defect, you'll work with a pediatric cardiologist to determine the best course of action. That may mean surgery in the first year of life, or it may mean monitoring the defect to see if it resolves on its own.

Modern surgical outcomes for AVSD, VSD, and ASD are excellent. Children who undergo successful repair typically live full, active lives with no long-term restrictions. The conversation you're having now with your cardiologist is about timing, preparation, and ensuring your child gets the care they need when they need it.