---
title: Atrial septal defect
description: What an atrial septal defect is, why it happens, how it is found and which treatment approaches clinical guidelines describe.
type: disease
preset: atrial-septal-defect
aliases:
  - ASD
  - hole in the heart
sources:
  - tier: guideline
    org: minzdrav-rf
    title: Дефект межпредсердной перегородки
    year: 2023
    doi: 10.15829/1560-4071-2023-5588
    url: https://cr.minzdrav.gov.ru/view-cr/46_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: statpearls
    title: Atrial Septal Defect
    year: 2025
    url: https://www.ncbi.nlm.nih.gov/books/NBK535440/
sources_checked: 2026-10-11
review: null
---

An atrial septal defect (ASD) is a congenital heart defect: there is a hole in the <Structure id="interatrial-septum">wall (septum) between the right and left atria</Structure>, and blood passes through it from one atrium to the other.<Cite n={1} /> A patent foramen ovale is not counted as an ASD.<Cite n={1} />

<Diagram name="atrial-septal-defect">
  <p slot="normal">Normally there is no hole in the wall between the atria.<Cite n={1} /></p>
  <p slot="disease">With an ASD, blood flows through the hole from the left atrium into the right, so the right side of the heart and the lungs receive extra blood.<Cite n={[1, 3]} /></p>
  <p slot="treated">After treatment the hole in the wall between the atria is closed: either with a device (occluder) passed to the heart through a blood vessel, or during open-heart surgery, where the defect is stitched shut or closed with a patch.<Cite n={1} /> The method of closure is chosen by doctors: a cardiologist and a cardiac surgeon.<Cite n={1} /> After either method, some blood may still pass between the atria (a residual shunt).<Cite n={1} /></p>
</Diagram>

## Why it happens

<Patient>

The defect forms before birth, when the wall between the atria does not develop completely.<Cite n={1} /> It sometimes occurs together with genetic syndromes such as Down syndrome, and the risk may be raised by rubella, alcohol or drugs (such as cocaine) in the mother during pregnancy.<Cite n={3} /> Blood flows through the hole from the <Structure id="left-atrium">left atrium</Structure> into the right, so the right side of the heart and the lungs receive extra blood.<Cite n={[1, 3]} />

Small defects often close on their own in the first year of life.<Cite n={3} /> ASD is more common in females.<Cite n={1} />

</Patient>

<Student>

The defect results from underdevelopment of the septum primum, septum secundum and endocardial cushions during embryonic development.<Cite n={1} /> The Russian Ministry of Health guideline distinguishes secundum ASD (80% of all ASDs), primum ASD (15%), sinus venosus defect, coronary sinus defect and common atrium.<Cite n={1} />

Right atrial pressure is lower than left atrial pressure, so blood is shunted from left to right.<Cite n={3} /> A persistent left-to-right shunt leads to pulmonary circulation overload (hypervolaemia) and pulmonary hypertension.<Cite n={1} />

The size of a secundum ASD can change with age: spontaneous closure occurs in 56% of patients with a 4–5 mm defect, 30% with 6–7 mm and 12% with 8–10 mm.<Cite n={1} />

</Student>

## Symptoms

<Patient>

ASD often causes no symptoms, especially in childhood.<Cite n={[1, 3]} /> Some people have tiredness and breathlessness on exertion, frequent colds and other respiratory infections, or slightly slower physical development.<Cite n={1} /> Adults may notice an irregular or skipping heartbeat and palpitations.<Cite n={1} /> Symptoms usually become more noticeable between the ages of 20 and 40.<Cite n={1} />

Over time ASD can lead to complications: high pressure in the lung blood vessels, heart rhythm problems, failure of the right side of the heart, and stroke.<Cite n={3} />

</Patient>

<Student>

Auscultation reveals a grade 2–3/6 systolic murmur in the second left intercostal space at the sternal border and fixed splitting of the second heart sound over the pulmonary artery.<Cite n={[1, 3]} /> Symptoms become more pronounced in the third and fourth decades of life.<Cite n={1} />

Complications:

- pulmonary arterial hypertension develops mainly in the third and fourth decades; its prevalence among adults with ASD is 8–10%;<Cite n={1} />
- with severe pulmonary hypertension and a veno-arterial (right-to-left) shunt, cyanosis may appear; Eisenmenger syndrome is a late complication;<Cite n={[1, 3]} />
- atrial arrhythmias (atrial flutter and atrial fibrillation) usually arise in adulthood;<Cite n={1} />
- paradoxical embolism from peripheral venous thrombi is a risk factor with defects of any size.<Cite n={1} />

</Student>

## How it is diagnosed

<Patient>

The doctor listens to the heart: a murmur is often heard with ASD.<Cite n={1} /> Next come an ECG and a chest X-ray, and the key test is an ultrasound scan of the heart (echocardiogram).<Cite n={[1, 3]} /> In adults, blood oxygen levels are checked with a pulse oximeter (a sensor on the finger) at rest and during exercise.<Cite n={1} /> If the defect is hard to see on a standard scan, the scan is done through the oesophagus (gullet), and before surgery a heart MRI may be arranged if the ultrasound results are unclear.<Cite n={1} />

</Patient>

<Student>

The ECG is checked for signs of right heart overload: right axis deviation and incomplete or complete right bundle branch block.<Cite n={1} /> The main diagnostic method is transthoracic echocardiography with colour Doppler.<Cite n={[1, 3]} /> Transoesophageal echocardiography is used when the defect cannot be clearly located; contrast-enhanced MRI is used when echocardiography is inconclusive and surgery is being planned.<Cite n={1} />

Cardiac catheterisation is performed when the estimated pulmonary artery systolic pressure is above 40 mm Hg, to determine pulmonary vascular resistance (PVR) and the reversibility of pulmonary hypertension.<Cite n={1} /> The European guideline states that in patients with shunt lesions and non-invasive signs of elevated pulmonary artery pressure, invasive measurement of PVR is mandatory.<Cite n={2} />

</Student>

## How it is treated

<Patient>

Medicines do not close the defect, so medication on its own is not recommended for an isolated ASD; in babies with heart failure, the doctor may prescribe medicines that ease its symptoms.<Cite n={1} /> If the hole is overloading the right side of the heart, it is closed.<Cite n={1} /> The most common type, secundum ASD, is closed without opening the chest if the size and shape of the defect allow: a special device (occluder) is passed through a blood vessel to the heart.<Cite n={1} /> Other types of defect are closed with open-heart surgery.<Cite n={[1, 3]} />

Surgery for an isolated ASD is not recommended in children under one year old, and closure through a blood vessel is preferably done after the age of 1.5–2 years.<Cite n={1} /> If the pressure in the lung blood vessels has become very high and irreversible, the defect can no longer be closed.<Cite n={[1, 2]} /> After surgery, physical activity is limited for a while, and after any method of closure people have regular check-ups with a cardiologist.<Cite n={1} /> Whether to close the defect, and how, is decided by the doctor together with the patient or the parents.

</Patient>

<Student>

Closure is recommended regardless of symptoms when there is right ventricular volume overload and either no signs of pulmonary hypertension on non-invasive testing or, on invasive assessment, a PVR index < 3 WU·m², Qp/Qs > 1.5 and a PVR to systemic vascular resistance ratio < 0.3.<Cite n={1} /> The ESC (using Wood units not indexed to body surface area), when Qp:Qs > 1.5, gives closure class I with PVR < 3 WU, class IIa with 3–5 WU, class IIb (fenestrated closure only) with PVR ≥ 5 WU that falls below 5 WU on targeted PAH treatment, and class III with PVR ≥ 5 WU despite treatment.<Cite n={2} /> Desaturation on exercise and Eisenmenger syndrome are contraindications to closure.<Cite n={[1, 2]} /> In paradoxical embolism, once other causes have been excluded, closure is recommended (class IIa) regardless of defect size, provided there is no pulmonary arterial hypertension and no left ventricular disease.<Cite n={1} />

Transcatheter closure is the preferred method for secundum ASD up to 36 mm with rims of at least 5 mm.<Cite n={1} /> Sinus venosus defects, coronary sinus defects and primum ASD are closed surgically.<Cite n={[1, 3]} /> The best results are achieved with intervention before the age of 25, and in older patients the decision on surgery takes age into account.<Cite n={[1, 2]} /> Closure is beneficial at any age, but closure after 40 apparently does not affect the rate of arrhythmias.<Cite n={1} />

After surgery, physical activity is restricted for up to 3 months from discharge; after surgical or transcatheter closure, prophylaxis of infective endocarditis is given for 6 months, and ECG and echocardiography are performed at follow-up visits.<Cite n={1} />

</Student>

## When to see a doctor

Take a child to a doctor if they tire quickly and get breathless on exertion, often have respiratory infections, or are behind in physical development.<Cite n={1} /> An adult should see a cardiologist if they have breathlessness and tiredness on exertion, an irregular or skipping heartbeat, or palpitations.<Cite n={1} /> People whose defect has already been closed need to attend their planned check-ups.<Cite n={1} /> If a doctor hears a heart murmur and suspects ASD, an ultrasound scan of the heart (echocardiogram) is recommended, even if there are no complaints.<Cite n={1} />

ASD can be complicated by stroke.<Cite n={3} /> If there are signs of a stroke (sudden weakness or numbness on one side of the body, difficulty speaking, a drooping face), call your local emergency number (112 in the EU, 911 in the US and Canada, 999 in the UK) straight away. As with any heart condition, call an ambulance for fainting, chest pain or severe breathlessness: this is the site's general safety rule, repeated at the bottom of every page.

<Quiz />