---
title: Atrioventricular septal defect
description: What an atrioventricular septal defect (atrioventricular canal) is, how its forms differ, how it is diagnosed and which treatment approaches clinical guidelines describe.
type: disease
aliases:
  - AVSD
  - atrioventricular canal defect
  - AV canal
  - endocardial cushion defect
sources:
  - tier: guideline
    org: minzdrav-rf
    title: Дефект предсердно-желудочковой перегородки (Атриовентрикулярный канал)
    year: 2024
    url: https://cr.minzdrav.gov.ru/view-cr/709_2
  - tier: guideline
    org: esc
    title: 2020 ESC Guidelines for the management of adult congenital heart disease
    year: 2020
    doi: 10.1093/eurheartj/ehaa554
    url: https://doi.org/10.1093/eurheartj/ehaa554
  - tier: reference
    org: msd-manuals
    title: Atrioventricular Septal Defect
    year: 2023
    url: https://www.msdmanuals.com/professional/pediatrics/congenital-cardiovascular-anomalies/atrioventricular-septal-defect
sources_checked: 2026-10-13
review: null
---

An atrioventricular septal defect (atrioventricular canal) is a congenital heart defect in which septal tissue is deficient or absent directly above and below a common atrioventricular valve.<Cite n={1} /> This common valve is present in every form of the defect: it lies at one level and may have a single opening or be divided into two.<Cite n={1} />

There are complete, transitional (intermediate) and partial forms.<Cite n={[1, 3]} /> The diagram shows the complete form.

<Diagram name="atrioventricular-septal-defect">
  <p slot="normal">
    Normally the right and left halves of the heart are separate, and blood flows from the atria
    into the ventricles through two separate valves: the tricuspid valve on the right and the mitral
    valve on the left.<Cite n={1} />
  </p>
  <p slot="disease">
    In the complete form there is one large defect in the centre of the heart: directly above the
    common valve is a defect between the atria, below it a defect between the ventricles, and both
    atria connect with the ventricles through this single valve.<Cite n={[1, 3]} /> Blood shunts from
    left to right at the atrial and the ventricular level, and all four heart chambers
    enlarge.<Cite n={3} />
  </p>
</Diagram>

## Why it happens

<Patient>

The defect forms before birth. While the baby's heart develops, areas of tissue called the endocardial cushions should divide the right and left halves of the heart and form two valves: the tricuspid and the <Structure id="mitral-valve">mitral valve</Structure>.<Cite n={1} /> When they develop abnormally, this defect results.<Cite n={[1, 3]} />

The defect is often linked with Down syndrome: most people with the complete form have Down syndrome, while in the partial form it is rare.<Cite n={[1, 2, 3]} /> For this reason, if the defect is found during pregnancy, the Russian Ministry of Health guideline provides for a consultation with a geneticist.<Cite n={1} />

Blood shunts from left to right through the defects, and the lungs receive extra blood.<Cite n={[1, 3]} /> In the complete form, the pressure in the right ventricle and the pulmonary artery approaches or equals the pressure in the systemic circulation.<Cite n={1} /> Resistance in the lung vessels rises quickly, and between 6 and 12 months of age, sometimes earlier, irreversible changes begin in their walls.<Cite n={1} /> Without surgery, the complete form can lead over time to [Eisenmenger syndrome](../eisenmenger-syndrome/): the shunt reverses direction and cyanosis (a bluish colour of the skin and lips) appears.<Cite n={[2, 3]} />

</Patient>

<Student>

Forms according to the Russian Ministry of Health guideline: complete — a primum atrial septal defect (ASD), a non-restrictive inlet ventricular septal defect (VSD) and a single atrioventricular (AV) valve.<Cite n={1} /> Transitional (intermediate) — two separate AV valves with a cleft in the anterior mitral leaflet, a primum ASD and usually a restrictive inlet VSD.<Cite n={1} /> Partial — a primum ASD without a VSD, with a cleft in the anterior mitral leaflet.<Cite n={1} /> According to the ESC, in a complete AVSD the central fusion is not present and there is only one orifice, whereas in the partial form the anterior and posterior bridging leaflets are fused centrally, creating separate left- and right-sided orifices.<Cite n={2} />

An unequal position of the common AV valve above the ventricles is accompanied by a variable degree of ventricular hypoplasia (unbalanced AVSD); according to the Russian guideline, it occurs in 7–10% of patients with AVSD.<Cite n={[1, 2]} /> The defect accounts for 3–6% of all congenital heart defects.<Cite n={1} /> It is most often combined with a secundum ASD and a patent ductus arteriosus; [tetralogy of Fallot](../tetralogy-of-fallot/) can also occur.<Cite n={[1, 2]} />

In the partial form, the shunt is at the atrial level only; the haemodynamics are similar to a secundum ASD, with the additional finding of variable degrees of AV valve regurgitation.<Cite n={[1, 3]} /> The risk of irreversible pulmonary hypertension is then much lower than when a VSD is also present.<Cite n={1} /> In children with Down syndrome, the risk of irreversible pulmonary vascular disease is higher, and it may develop earlier.<Cite n={[1, 3]} />

</Student>

<HeartModel highlight={['interatrial-septum', 'interventricular-septum', 'mitral-valve', 'tricuspid-valve']} />

## Symptoms

<Patient>

In the complete form with a large shunt, signs of [heart failure](../heart-failure/) appear early — by 4 to 6 weeks of age.<Cite n={3} /> Parents may notice breathlessness, including during feeding and crying, sweating during feeds, refusing the breast, poor weight gain, frequent respiratory infections and a fast heartbeat.<Cite n={1} /> Without surgery, most children with the complete form die in the first 3–5 years of life.<Cite n={1} />

The partial form, when the left valve leaks only mildly, resembles an [atrial septal defect](../atrial-septal-defect/) and rarely causes problems before the age of one.<Cite n={[1, 3]} /> Symptoms increase with age; according to the ESC, most adults with an unoperated partial form have symptoms by the age of 40.<Cite n={2} /> These include reduced exercise tolerance, breathlessness, tiredness, palpitations and heart rhythm disturbances.<Cite n={[2, 3]} /> Cyanosis usually means that pulmonary hypertension has developed or that the defect is combined with other heart defects.<Cite n={1} />

</Patient>

<Student>

On auscultation there is a systolic murmur of varying intensity and an accentuated second heart sound over the pulmonary artery; as pulmonary hypertension progresses, the murmur may become softer.<Cite n={1} /> With persistently raised pulmonary vascular resistance, especially in Down syndrome, there may be no murmur, but a loud single S2 is present.<Cite n={3} /> With a large VSD component or significant AV valve regurgitation, tachypnoea, tachycardia and hepatomegaly are common.<Cite n={3} />

In the partial form, deterioration, usually in adulthood, is often linked with atrial fibrillation due to persistent volume overload.<Cite n={1} />

</Student>

## How it is diagnosed

<Patient>

The main test is an ultrasound scan of the heart (echocardiography) with Doppler: it shows the defects, the structure of the valve, how much it leaks, the direction of the shunt and how the ventricles work.<Cite n={[1, 2, 3]} /> An ECG and a chest X-ray are also done: the X-ray shows an enlarged heart and increased lung markings.<Cite n={[1, 3]} /> If there are signs of high pressure in the pulmonary artery, it is measured through a catheter to find out whether the changes in the lung vessels are reversible and whether surgery is possible.<Cite n={[1, 2]} />

</Patient>

<Student>

Echocardiography is the key diagnostic technique: it assesses each anatomic component of the defect, the AV valves, the severity and exact substrate of AV valve regurgitation, the magnitude and direction of intracardiac shunting, the function of both ventricles, pulmonary artery pressure and left ventricular outflow tract obstruction (LVOTO).<Cite n={2} />

The ECG shows left-axis deviation, often a prolonged PR interval (first-degree [AV block](../av-block/)) and signs of right ventricular hypertrophy (rsR′).<Cite n={[1, 3]} /> The ESC explains the prolonged AV conduction and left-axis deviation by the posterior displacement of the bundle of His and the left bundle branch.<Cite n={2} /> The chest X-ray shows cardiomegaly, increased pulmonary vascular markings and a prominent pulmonary artery segment.<Cite n={[1, 3]} />

Cardiac MRI is indicated when additional quantification of the ventricles, AV valve regurgitation or shunting is required for decision making; cardiac catheterisation is required in case of non-invasive signs of raised pulmonary artery pressure.<Cite n={2} /> The Russian guideline recommends invasive pulmonary artery pressure measurement with drug testing in patients older than 6 months with severe pulmonary hypertension, to establish the reversibility of pulmonary vascular disease and operability.<Cite n={1} />

</Student>

## How it is treated

<Patient>

Treatment is surgical: the defect itself is the reason for surgery, and it cannot be closed with a device passed through a blood vessel.<Cite n={[1, 2]} /> The surgeon closes the defects with a patch and divides the common valve into two — a right and a left valve — while taking care not to damage the heart's conduction system.<Cite n={1} /> The surgeon chooses the operative technique.<Cite n={1} />

The timing of surgery depends on the form of the defect and the child's condition.<Cite n={1} /> The complete form is usually repaired in the first months of life, and earlier if heart failure is severe.<Cite n={[1, 3]} /> When and how to operate is decided by the cardiologist and the cardiac surgeon.<Cite n={1} />

Before surgery, heart failure is treated with medicines, mainly diuretics; if they do not help, surgery is done regardless of age and weight.<Cite n={1} /> If the changes in the lung vessels are irreversible, including in Eisenmenger syndrome, surgery is contraindicated.<Cite n={[1, 2]} />

With timely surgery the outlook is good, and most people whose recovery after surgery was uncomplicated have no limits in daily life.<Cite n={1} /> The most common problem after surgery is a leaking left valve; if the leak is significant, another operation may be needed.<Cite n={[1, 2]} /> A residual defect, narrowing of the outflow from the left ventricle and complete [AV block](../av-block/), which needs a permanent pacemaker, can also occur.<Cite n={1} /> This is why lifelong follow-up by a cardiologist is needed — both after surgery and without it, including in specialised centres for adults with congenital heart disease.<Cite n={[1, 2]} />

Pregnancy is usually well tolerated after complete repair with no significant residual problems, but it is not recommended when the pressure in the lung vessels is high.<Cite n={2} /> Children of people with this defect have congenital heart defects more often.<Cite n={1} />

</Patient>

<Student>

The aims of surgery according to the Russian guideline: close the interatrial and, if present, the interventricular communication, avoid damage to the AV node and the bundle of His, and create two competent AV valves without haemodynamically significant stenosis.<Cite n={1} /> Techniques include the two-patch, the single-patch and the modified single-patch repair; the choice depends on the surgeon's preference and experience.<Cite n={1} /> In the partial form, repair consists of closure of the primum ASD and repair of the mitral valve.<Cite n={1} />

Pulmonary artery banding as a first stage is not recommended, except in small children in an extremely severe condition.<Cite n={1} /> In an unbalanced form not suitable for a biventricular or one-and-a-half ventricle repair, staged surgery is performed, ultimately with a Fontan procedure.<Cite n={[1, 3]} />

ESC, for adults with balanced AVSD: in the partial form, surgical closure is recommended in patients with significant right ventricular volume overload; valve surgery, preferably AV valve repair, is recommended in symptomatic patients with moderate to severe AV valve regurgitation; surgery should be performed by a congenital cardiac surgeon.<Cite n={2} /> The left AV valve differs from the mitral valve and is more difficult to repair.<Cite n={2} />

LVOTO is rarely found before surgery and usually develops after it, in the early or the late postoperative period.<Cite n={1} />

</Student>

## When to call an ambulance

In a child with this defect, worsening heart failure is a reason for hospital admission: with severe heart failure, many organs are quickly affected.<Cite n={1} /> Its signs are breathlessness at rest or when crying and feeding, a fast heartbeat, sweating and poor appetite.<Cite n={1} /> If these signs are getting worse quickly — the child is breathless even at rest or stops feeding from the breast or bottle — call your local emergency number (112 in the EU, 911 in the US and Canada, 999 in the UK).<Cite n={1} />

After surgery, during the first 30 days after discharge, fluid around the heart and [cardiac tamponade](../cardiac-tamponade/) can occur; a fever or unusual symptoms — chest or abdominal pain, vomiting, increasing tiredness — should be reported to the cardiologist.<Cite n={1} /> The most severe rhythm disturbance with this defect is complete AV block;<Cite n={1} /> fainting is a reason to call an ambulance straight away. As with any heart condition, call your local emergency number (112 in the EU, 911 in the US and Canada, 999 in the UK) for fainting, chest pain or severe breathlessness: this is the site's general safety rule, repeated at the bottom of every page.

<Quiz />