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Health condition · Clinically reviewed

Atrioventricular canal defect, one hole, one common valve, one clear plan.

A congenital heart defect where the endocardial cushions fail to fuse. Modern paediatric cardiac surgery in the first six months of life gives most children a normal life expectancy.

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A radiographer guides a patient onto the bed of an advanced 3 Tesla MRI scanner in a London imaging suite

Why trust this guide

  • 01

    Clinically reviewed

    Written by our editorial team and reviewed by a registered UK clinician before publication.

  • 02

    Sourced from guidance

    Checked against NICE, NHS England paediatric cardiac networks and specialist society guidance you can see at the end.

  • 03

    Current for 2026

    Reflects modern UK practice including early surgical repair at 3 to 6 months and lifelong ACHD follow-up.

Key facts

AVCD at a glance.

The essentials, in plain English. What the defect is, why it happens and how it is treated in the UK today.

  • What it is

    A congenital heart defect where the endocardial cushions fail to fuse, leaving a hole between the atria and ventricles and a single common atrioventricular valve.

  • Other names

    Also called atrioventricular septal defect (AVSD) or endocardial cushion defect. Complete, partial, transitional and intermediate variants exist.

  • Down syndrome link

    Around 40 to 50 per cent of babies with a complete AVCD have Down syndrome, and 40 per cent of Down syndrome infants with heart disease have an AVCD.

  • Presentation

    Complete AVCD causes heart failure in the first weeks to months of life; partial AVCD may be silent until school age or later.

  • Treatment

    Surgical repair is the definitive treatment. Complete AVCD is repaired at 3 to 6 months, before pulmonary vascular disease becomes irreversible.

  • Long-term outlook

    Modern surgical results are excellent, but lifelong adult congenital heart disease (ACHD) follow-up is needed for valve function and rhythm.

Types

One defect, four variants.

AVCD sits on a spectrum. The four variants share an embryological origin but differ in the size of the shunt, the valve anatomy and the timing of surgery.

  • Complete AVCD

    A primum atrial septal defect, an inlet ventricular septal defect and a single five-leaflet common atrioventricular valve straddling both ventricles. The Rastelli A, B and C classification describes where the valve chordae attach.

  • Partial AVCD

    An ostium primum atrial septal defect with a cleft in the mitral valve and an intact ventricular septum. Behaves like an ASD and often presents later in childhood or adulthood.

  • Transitional AVCD

    A primum ASD with a small, restrictive inlet VSD and two separate atrioventricular valve orifices. Symptoms and surgery sit between the partial and complete forms.

  • Intermediate AVCD

    Similar to the complete form but with two separate atrioventricular valve orifices. Repair follows the same principles as complete AVCD.

How the diagnosis is made

From fetal scan to a clear surgical plan.

The steps a UK paediatric cardiology team will normally follow, in order, so you know what to expect and why.

  1. 01

    Assessing

    Antenatal or newborn detection

    Many AVCDs are picked up on the 20-week fetal anomaly scan or during newborn examination with a murmur and abnormal pulse oximetry.

  2. 02

    Assessing

    Clinical assessment

    Hyperactive precordium, fixed split second heart sound, systolic ejection murmur and an apical pansystolic murmur from AV valve regurgitation.

  3. 03

    Assessing

    ECG

    A superior QRS axis with left-axis deviation is classic. PR-interval prolongation and right ventricular hypertrophy are common.

  4. 04

    Confirming

    Chest X-ray

    Cardiomegaly and pulmonary plethora reflect the large left-to-right shunt through the combined atrial and ventricular defect.

  5. 05

    Confirming

    Transthoracic echocardiogram

    The gold-standard test. Delineates the atrial and ventricular components, AV valve anatomy, shunt direction and an estimate of pulmonary pressure.

  6. 06

    Confirming

    Cardiac MRI and catheterisation

    MRI quantifies ventricular volumes and shunt. Catheterisation measures pulmonary vascular resistance in older infants and adults where Eisenmenger risk is a concern.

  7. 07

    Planning

    Genetic testing

    Karyotype for Down syndrome is offered to every infant with AVCD. Heterotaxy panels are considered where the anatomy suggests laterality disturbance.

Typical timeline: from newborn diagnosis to definitive surgery within the first six months.

Symptoms

What AVCD actually looks like.

Feeding, breathing and growth are the early clues in infants. Adults with unrepaired disease present with breathlessness, arrhythmia or cyanosis.

  • Poor feeding and failure to thrive

    The classic early sign of complete AVCD. Babies tire quickly at the breast or bottle, feed for shorter periods and gain weight slowly.

  • Tachypnoea and sweating

    Rapid, laboured breathing with sweating during feeds reflects heart failure from the large left-to-right shunt.

  • Recurrent chest infections

    Pulmonary over-circulation makes lower respiratory infections more frequent and more severe than expected for age.

  • Hepatomegaly

    An enlarged liver is a bedside sign of right-sided congestion and heart failure in infants with a large AVCD.

  • Murmur on auscultation

    A fixed split second sound, a pulmonary flow murmur and an apical pansystolic murmur of AV valve regurgitation are the classic mix.

  • Cyanosis and clubbing (late)

    Late signs suggesting pulmonary vascular disease and shunt reversal. A red flag for possible Eisenmenger physiology.

  • Adult ACHD presentation

    Partial or unrepaired AVCD in adults presents with exertional breathlessness, arrhythmia, right-heart failure or a stroke from paradoxical embolism.

  • Red flag - Eisenmenger physiology

    Deep cyanosis, syncope, haemoptysis or right heart failure in an unrepaired adult AVCD. Surgical closure is then contraindicated.

Treatment

How AVCD is treated in the UK.

Definitive surgical repair in a paediatric cardiac surgery centre, supported by heart-failure medicines, nutrition and lifelong congenital cardiology follow-up.

  • Surgical repair of complete AVCD

    Patch closure of the atrial and ventricular defects with division of the common valve into two functional AV valves and cleft closure, at 3 to 6 months of age.

  • Surgical repair of partial AVCD

    Primum ASD closure with cleft mitral valve repair, usually at 2 to 5 years or earlier if symptomatic or the shunt is large.

  • Pulmonary artery banding

    A palliative option in very small or unwell infants to protect the lungs and buy time before definitive repair.

  • Diuretics

    Furosemide and spironolactone unload the failing heart and improve feeding and breathing while awaiting surgery.

  • ACE inhibitor and digoxin

    Standard heart-failure medicines used pre-operatively to reduce afterload and support cardiac output in infants with a large shunt.

  • High-calorie nutrition

    Fortified feeds and, where needed, nasogastric feeding protect growth in the months before surgery.

  • Endocarditis prophylaxis

    Antibiotic cover is recommended for the first six months after repair and lifelong where prosthetic material or residual defects remain.

  • Pulmonary hypertension therapies

    For adults with Eisenmenger physiology, disease-targeted therapies (endothelin antagonists, PDE-5 inhibitors, prostacyclins) improve symptoms and survival.

Where surgery happens

UK paediatric cardiac surgery centres.

Complex neonatal and infant repair is concentrated in a small number of high-volume paediatric cardiac surgery units, including Great Ormond Street, Alder Hey, Birmingham Children's, Bristol Royal Hospital for Children, Leeds and the Royal Hospital for Sick Children in Edinburgh.

What this guide is based on

The sources behind every claim on this page.

UK national guidance and specialist society standards, current at the time of last review.

Key references

Guidelines and standards we relied on.

A quiet reminder

This guide is for information, not medical advice.

Your paediatric cardiologist or ACHD consultant knows your child and history and can tell you which parts apply to your family. If in doubt, get seen.

  • NICE. Congenital heart disease in children and young people: pathways of care.

  • NHS England. Paediatric and Congenital Cardiac Services (Specialised Commissioning).

  • European Society of Cardiology. Guidelines for the management of adult congenital heart disease.

  • British Congenital Cardiac Association. Standards for the management of atrioventricular septal defects.

Red flags

When AVCD needs urgent attention.

Most AVCD is picked up early and repaired safely. These are the situations that need same-day cardiology or emergency review.

  • Cyanosis in a newborn

    Any newborn with persistent central cyanosis needs urgent paediatric cardiology assessment and echocardiography to look for a duct-dependent lesion or complex AVCD.

  • Failure to thrive with tachypnoea

    A baby who sweats and tires during feeds and drops through the weight centiles needs urgent cardiac review, not reassurance.

  • Recurrent chest infections

    Repeated hospital admissions for bronchiolitis or pneumonia in an infant should prompt an ECG, chest X-ray and echocardiogram.

  • Missed antenatal diagnosis

    Around a third of AVCDs are missed on the 20-week scan. A postnatal murmur or abnormal saturations should never be dismissed as innocent.

  • Late presentation over one year

    Repair after 12 months carries a rising risk of irreversible pulmonary vascular disease. Urgent catheterisation is needed to assess suitability for surgery.

  • Eisenmenger physiology

    Deep cyanosis and clubbing in an unrepaired adult mean pulmonary pressures are systemic. Closure is contraindicated and specialist PAH care is needed.

  • Complete heart block after repair

    A recognised complication of surgery. New syncope, bradycardia or fatigue in a repaired patient needs urgent ECG and pacemaker assessment.

  • New arrhythmia in ACHD

    Atrial flutter or fibrillation in a repaired AVCD raises stroke risk and needs prompt anticoagulation and rhythm management.

  • Pregnancy in unrepaired AVCD

    Any pregnancy in a woman with unrepaired or partially repaired AVCD needs pre-conception counselling and joint obstetric-cardiac care.

Living with it

A treatable defect, with a lifelong plan.

Four things that make the biggest difference over a lifetime with AVCD: a named specialist centre, feeding support before surgery, structured transfer to adult care and clear advice on pregnancy, sport and dentistry.

A quiet reminder

Follow-up never really stops.

Even after a textbook repair, valve function and rhythm are watched for life at an adult congenital heart disease service.

  1. 01 Team

    A named specialist centre

    Care is delivered by one of the UK paediatric cardiac networks (Great Ormond Street, Alder Hey, Birmingham Children's, Bristol Royal Hospital for Children, Leeds and Edinburgh Royal).

  2. 02 Growth

    Feeding and growth support

    A dietician and specialist nurse help protect growth before surgery. Small, fortified feeds and, where needed, tube feeding are common.

  3. 03 Transition

    Paediatric to adult transfer

    A structured move from paediatric cardiology to an adult congenital heart disease (ACHD) service happens between 16 and 18 years of age.

  4. 04 Life

    Pregnancy, sport and dentistry

    Most repaired patients can exercise, work and start a family. Pregnancy planning, sport advice and endocarditis cover for dentistry are all covered at follow-up.

Frequently asked

Everything we get asked about AVCD.

Quick answers on types, the Down syndrome link, timing of surgery and long-term follow-up.

  • What is an atrioventricular canal defect?

    It is a congenital heart defect in which the endocardial cushions fail to fuse in early pregnancy, leaving a combined atrial and ventricular septal defect and a single common atrioventricular valve. It is also called an atrioventricular septal defect (AVSD) or endocardial cushion defect.

  • Why is it linked to Down syndrome?

    The endocardial cushions form under tight genetic control, and trisomy 21 disrupts that process. Around 40 to 50 per cent of babies with a complete AVCD have Down syndrome, and roughly 40 per cent of Down syndrome babies with congenital heart disease have an AVCD.

  • When is surgery done?

    A complete AVCD is repaired at 3 to 6 months of age, before the lungs develop irreversible pulmonary vascular disease. Partial AVCD is usually repaired between 2 and 5 years, earlier if the shunt is large or the child is symptomatic.

  • What does the operation involve?

    The surgeon closes the atrial and ventricular components with patches, divides the common atrioventricular valve into two functional valves and closes any cleft in the mitral valve. It is a high-volume paediatric cardiac procedure with excellent published outcomes.

  • What are the long-term complications?

    The commonest is regurgitation of the left atrioventricular valve, which can need re-operation. Complete heart block, residual shunts, left ventricular outflow tract obstruction and arrhythmia are also recognised.

  • Do adults with a repaired AVCD need ongoing care?

    Yes. Everyone with a repaired AVCD needs lifelong follow-up at an adult congenital heart disease (ACHD) centre for valve function, rhythm and pulmonary pressures. Endocarditis prophylaxis, pregnancy counselling and sport advice are part of that care.

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