What is AVSD?
An atrioventricular septal defect (AVSD), also called open atrioventricular canal, is a developmental defect of the central part of the heart. In a healthy heart, the septum between the atria, the septum between the ventricles, and two separate valves (mitral and tricuspid) all form independently. In AVSD, these structures do not complete their development: a defect in the lower part of the atrial septum, a defect in the upper part of the ventricular septum, and a shared abnormal valve — all present at once.
As a result, all four chambers of the heart communicate with one another, blood flows in the wrong directions, and the valve does not close fully. This places an enormous burden on the heart and lungs.
AVSD occurs in two forms. Complete AVSD — a large defect in both septa, with the valves forming as a single common defective valve. Partial AVSD — a defect only in the atrial septum with mitral valve regurgitation; the ventricular septum is intact.
"AVSD is a complex defect, but with timely surgery the results are excellent. I perform this operation every week. Parents are often terrified by the diagnosis — but the real situation is considerably more encouraging than they imagine."
AVSD and Down syndrome
AVSD is particularly significant because it is extremely common in children with Down syndrome (trisomy 21). Of children with Down syndrome, 40–50% have a heart defect, and more than half of those defects are AVSD.
This association is so strong that when Down syndrome is diagnosed prenatally or postnatally, the heart must be examined by echocardiography without delay. Early detection means the opportunity for early treatment.
AVSD also occurs in children without Down syndrome. All patients with this diagnosis receive the same high-level cardiac surgical care.
Symptoms in children
Symptoms depend on whether the defect is complete or partial, and on severity. Complete AVSD typically appears in the first weeks of life:
- Heavy sweating during feeding, rapid fatigue, feeding in short bursts with breaks
- Poor weight gain — the child is not growing normally
- Frequent respiratory tract infections, pneumonia
- Shortness of breath, rapid breathing
- In some cases — bluish discolouration of the lips and nail beds (cyanosis)
- Prominent heart murmur — the paediatrician hears it on examination
Partial AVSD may produce milder symptoms and is sometimes detected later in childhood.
Important: If complete AVSD is left untreated, irreversible changes in the pulmonary blood vessels — Eisenmenger syndrome — begin developing within the first 6 months of life. Once this occurs, surgery is no longer possible. This is precisely why, when AVSD is diagnosed in the first months, the operation is performed as soon as possible.
Diagnosis
When AVSD is suspected, the key investigation is echocardiography (echo). It shows the complete anatomy of the defect: the condition of both septa, the structure of the valves, and the direction of blood flow. All the information needed to plan surgery comes from the echo.
Prenatal diagnosis is possible: fetal echocardiography from 18–22 weeks of pregnancy can identify AVSD. This gives parents the opportunity to prepare, plan delivery in a specialised centre, and have cardiac surgical support ready from the child's first minutes of life.
Surgery: when and how
For complete AVSD, the optimal age is 3–6 months. Within this window, irreversible damage to the pulmonary vasculature has not yet occurred, while the child already tolerates surgery much better.
The operation is performed on the open heart under cardiopulmonary bypass. The defects in both septa are closed with patches; the valves are reconstructed with maximum preservation of the child's own tissue. The technical challenge lies in anatomically accurate reconstruction of the valve apparatus — which is highly dependent on surgical experience.
For partial AVSD, timing is more flexible — usually planned between ages 2 and 5, though earlier surgery is possible depending on defect size and symptom severity.
What to expect after surgery
After a successful operation, the majority of children live a normal life. However, children with AVSD need lifelong cardiology follow-up — mitral valve function requires monitoring over time, and in rare cases an additional valve-related procedure may become necessary in the future.
The question of sport is decided individually. Most children can return to normal physical activity within a few months of surgery. Intensive competitive sport is discussed with the cardiologist.
"The conversations with parents of children with AVSD that I remember best are the ones 6 months, 1 year, 3 years after the operation. The child is growing, developing, laughing. Those moments remind me of the value of every surgery."
Questions and answers
Can AVSD close on its own?
No. AVSD does not close spontaneously. It is a defect that requires surgical intervention without fail. Delay can cause irreversible damage to the pulmonary vasculature.
Isn't 3 months too early for surgery?
On the contrary — for complete AVSD, 3–6 months is the optimal window. Waiting increases the risks. Modern paediatric cardiac surgery can operate even on newborns; a three-month-old already tolerates the procedure well.
Are outcomes different in children with Down syndrome?
Surgical outcomes are comparable to those in children without Down syndrome. The success rate is the same. In the long term, valve function is carefully monitored, and most children show a good result.
Will a second operation be needed?
For the majority of children one operation is sufficient. Mitral valve function is monitored over time — in rare cases a valve-related procedure may be needed in the future. I don't want to create unnecessary worry in advance, because for most children this does not happen.
AVSD was found during pregnancy — what should we do?
Confirm the diagnosis with fetal echocardiography. Plan delivery at a specialised perinatal-cardiology centre. Meet with a paediatric cardiac surgeon in advance. A prenatal diagnosis is an advantage, not a setback — it gives you time to prepare.