Education for families living with congenital heart conditions
Heart Up Close
Your Journal
HomeHeart conditions
Choose an explanation

Your child’s diagnosis

Atrial septal defect (ASD)

Your Journal

When to get help

01

How blood flows

Atrial septal defect (ASD)

The same region in both views. The usual view is a comparison, not a treatment result.

Follow the connections

ASD · a connection between atria

ASD · a connection between atriaSimplified isolated defect after birth, showing the common left-to-right pattern after lung resistance falls. Flow amount and direction vary with opening size, pressures, lung resistance and other anatomy; newborn transition and reversed shunts are not shown. Colours show relative oxygen content, not measured saturation. Structural focus: Left atrium, Right atrium, ASD gap. Arrows show direction. This diagram does not measure blood flow, oxygen levels or severity. BodyBodyRight atriumRARight ventricleRVLeft atriumLALeft ventricleLVLungsLungsASD gap
  • Less oxygen
  • Mixed blood
  • More oxygen
RA Right atriumRV Right ventricleLA Left atriumLV Left ventricle

Step 1 of 3

An opening between the collecting chambers

An ASD is an opening in the septum between the left and right atria. Locate the gap between LA and RA.

How to read this map

Follow the arrows to see connections. This is a map, not the shape or position of a heart. Both sides work together; the story follows one part at a time. A crossing with a white gap is not a connection; a dot marks a junction. With story controls focused, use left/right arrows, Home or End.

Simplified isolated defect after birth, showing the common left-to-right pattern after lung resistance falls. Flow amount and direction vary with opening size, pressures, lung resistance and other anatomy; newborn transition and reversed shunts are not shown. Colours show relative oxygen content, not measured saturation.

Colours describe this example: blue means less oxygen, red more oxygen, and purple mixing. Blood is always red in real life. Line widths and animation do not measure flow, pressure, oxygen saturation or severity.

Diagram sources and scope

Simplified isolated defect after birth, showing the common left-to-right pattern after lung resistance falls. Flow amount and direction vary with opening size, pressures, lung resistance and other anatomy; newborn transition and reversed shunts are not shown. Colours show relative oxygen content, not measured saturation.

Original Heart Up Close connection map · Source check: 26 October 2026 · Independent clinical review pending.

Atrial septal defect (ASD)

  1. An opening between the collecting chambers. An ASD is an opening in the septum between the left and right atria. Locate the gap between LA and RA.
  2. Some blood crosses from LA to RA. In this common pattern after birth, some oxygen-rich blood moves through the opening from LA to RA, joining blood returning from the body.
  3. Through the right pump to the lungs. The extra blood travels from RA to RV and then to the lungs again. The amount depends on the opening and how the heart and lung circulation fill and resist flow.

Simplified isolated defect after birth, showing the common left-to-right pattern after lung resistance falls. Flow amount and direction vary with opening size, pressures, lung resistance and other anatomy; newborn transition and reversed shunts are not shown. Colours show relative oxygen content, not measured saturation.

02

Diagnosis and care

Diagnosis and tests

Many children with an ASD feel well. A doctor or nurse may first suspect it after hearing a murmur, an extra sound during the heartbeat. Some ASDs are seen during pregnancy. Others are found much later. Breathlessness, tiredness or slow growth may lead to tests. Even without symptoms, the team needs to check how the opening affects the heart.

An echocardiogram, or echo, is an ultrasound scan of the heart. It shows the opening, nearby parts of the heart and blood flow. An ECG records the heart’s electrical signals. Sometimes the team needs an MRI or CT, scans that give more detailed pictures. They may use a catheter test, which passes a thin tube through a blood vessel towards the heart.

Ask what each test will help them decide.

Care and follow-up

Some small openings get smaller or close on their own. Others need regular checks. The team may suggest closing an opening that allows a lot of extra blood to pass through. A device passed through a thin tube, called a catheter, can close some secundum ASDs. Other types may need surgery. Medicines do not close an ASD.

Ask which option suits your child’s opening and why.

The opening’s position and edges affect treatment choices. Nearby veins and valves, and blood pressure in the lungs, also matter. Checks after closure look at the result and any remaining problems. A primum ASD can also be described as a partial AVSD. This involves the middle of the heart and a valve as well as an opening. Ask the team to explain the full diagnosis.

Daily life

If a child feels well while waiting for a decision, ask what the team is monitoring and when they will reconsider the plan. Ask whether there are any precautions for PE, swimming or sports and how you should explain these to school.

03

Questions to ask

Save the questions you want to take to your next appointment. You can edit them in your Journal.

  • Which type of ASD does our child have, and how does that affect the care you recommend?
  • Is the right side of our child’s heart enlarged, and what does the scan tell you about its workload?
  • Are the heart valves and veins from the lungs connected as expected, or are there other differences we should understand?
  • Could the opening be closed using a device passed through a thin tube, and what makes that suitable or unsuitable for our child?
  • What checks would our child need after treatment, and what would you be looking for at each visit?
Go to Journal panel
Sources and review

Sources checked 9 October 2026. Independent clinical review pending.

Useful next guides

Choose what is relevant to your family.