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Screenings by age and gender

Enlarged left atrium seen by chance on an echo

An echocardiogram (heart ultrasound) done for another reason may report a "mildly enlarged", "dilated" or "borderline" left atrium. The left atrium is the upper chamber on the left side of the heart, which collects blood from the lungs before it passes to the main pumping chamber. In a large community study it was enlarged in about 6% of adults aged 35 and over, more often with age. (Ou 2016)(Ancona 2014) This page covers what the report means and the checks guidance lists, not treatment.

What the report means

  • What it is. The left atrium is larger than the reference range. Its size reflects how hard the main pumping chamber is to fill and how long pressure in the left atrium has been raised. (Ancona 2014)
  • What goes with it. In the community study, an enlarged left atrium was more common with older age, female sex, higher systolic blood pressure, a higher body mass index and diabetes; body mass index had the strongest link. (Ou 2016)
  • Other causes. It is also seen with atrial fibrillation, heart valve disease, high blood pressure, heart failure and cardiomyopathy. (Ancona 2014) In people who do a lot of endurance training, some enlargement is expected. (Spencer 2024)

How the size is measured

  • Volume for body size. The usual measure is the left atrial volume divided by body surface area (LAVi, in mL/m2). A single front-to-back diameter is an older measure that underestimates the volume. (Ancona 2014)(BSE 2020)
  • American and European bands. The American Society of Echocardiography and the European imaging association use 16 to 34 mL/m2 as normal, 35 to 41 as mildly, 42 to 48 as moderately and over 48 as severely enlarged, the same for women and men. (Spencer 2024)
  • British bands. The British Society of Echocardiography calls 34 mL/m2 or less normal, 34 to 38 borderline, and over 38 enlarged. A borderline value on its own counts as normal. (BSE 2020)

How common it is by age

In the community study of 10,574 adults, an enlarged left atrium by diameter was found in: (Ou 2016)

  • 3.6% of people aged 35 to 44
  • 5.4% aged 45 to 54
  • 8.9% aged 55 to 64
  • 11.4% aged 65 and over

The link to atrial fibrillation

  • A marker, not a diagnosis. A larger left atrium is linked to a higher chance of atrial fibrillation (an irregular heartbeat) and stroke. (Ancona 2014)
  • Size alone adds little to prediction. In 1,786 Framingham adults with a mean age of 66, 145 developed atrial fibrillation over 8.3 years; adding left atrial size to the usual risk models did not make them predict atrial fibrillation better. (Sardana 2018) In 1,866 Copenhagen adults followed for 16.5 years, left atrial volume was not linked to stroke once other factors were counted, while how well the atrium emptied was. (Larsen 2022)
  • Atrial fibrillation can be silent. The NHS says it sometimes causes no symptoms and is found at a routine check or during tests for something else. (NHS) Its risk rises with age, especially over 65. (MedlinePlus)

Checks guidance lists next

  • Blood pressure. The USPSTF recommends blood pressure screening for all adults. (USPSTF 2021) See blood pressure screening.
  • Pulse check. NICE advises feeling the pulse for an irregular beat when atrial fibrillation is suspected, including in people with breathlessness, palpitations, fainting or dizziness, chest discomfort, or a stroke or mini-stroke. (NICE NG196)
  • ECG. If the pulse is irregular, NICE advises a 12-lead ECG to make the diagnosis, with or without symptoms. (NICE NG196)
  • Screening without symptoms. For adults 50 and older without symptoms, the USPSTF finds the evidence insufficient to recommend for or against screening for atrial fibrillation. (USPSTF 2022) See atrial fibrillation screening.

How it ties to your age-based checks

An enlarged left atrium found by chance is a good time to make sure your routine checks are up to date:

Other heart findings have their own pages: thick heart muscle on an ECG or echo, mild leaky heart valve on an echocardiogram, mitral valve ring calcium and enlarged heart on a chest X-ray.

Who it applies to

Adults told that an echocardiogram done for another reason shows a mildly enlarged or borderline left atrium. Children, and people already followed by a heart specialist for atrial fibrillation, valve disease or heart failure, are outside this page.

The NHS says to see a GP if you think you have symptoms of atrial fibrillation or have palpitations that keep happening or get worse. It says to call 999 (911 in the US) if you have a fast or irregular heartbeat with chest pain, shortness of breath, fainting or dizziness, weakness or numbness on one side of the face or body, loss of sight, or confusion or difficulty speaking. (NHS)

Routine age-based screening

A finding on an echocardiogram does not replace the routine screenings for your age. See screenings by age and gender.

Where they differ:

  • Where enlarged starts. The American and European imaging societies call a volume index over 34 mL/m2 enlarged. (Spencer 2024) The British Society of Echocardiography calls 34 to 38 borderline and only over 38 enlarged, because healthy people in a large European study had larger values than earlier work suggested. (BSE 2020)
  • Age. British guidance says left atrial volume does not change with normal ageing, so the same limits apply at every age. (BSE 2020) Population studies still find enlargement more often in older adults, alongside higher blood pressure and weight. (Ou 2016)
  • Diameter or volume. Some studies define enlargement by diameter (over 4.0 cm in men, 3.8 cm in women). (Ou 2016) British guidance does not advise using diameter routinely. (BSE 2020)
  • Checking for atrial fibrillation. NICE advises a pulse check when atrial fibrillation is suspected, such as with symptoms. (NICE NG196) The USPSTF makes no recommendation for or against screening adults 50 and older who have no symptoms. (USPSTF 2022)

Your doctor decides what your result means for you.

Questions people ask

How common is an enlarged left atrium?

In a community study of 10,574 adults aged 35 and over, 6.4% had an enlarged left atrium by diameter, rising from about 3.6% at 35 to 44 to about 11.4% at 65 and over. (Ou 2016)

What do the numbers on my echo report mean?

The size is usually given as a volume divided by body size (mL/m2). The American and European imaging societies call up to 34 normal, 35 to 41 mildly enlarged, 42 to 48 moderately and over 48 severely enlarged. British guidance calls 34 to 38 borderline and over 38 enlarged. (Spencer 2024) (BSE 2020)

Does it mean I have atrial fibrillation?

No. An enlarged left atrium is linked to a higher chance of atrial fibrillation later, but it is not the same thing. A pulse check and a 12-lead ECG are how atrial fibrillation is found. (Ancona 2014) (NICE NG196)

Can exercise make the left atrium bigger?

Yes. In people who do a lot of endurance training, some enlargement of the left atrium is expected as part of the "athlete's heart". (Spencer 2024)

What checks are usual next?

Guidance lists a blood pressure check for all adults, and a pulse check with a 12-lead ECG if the pulse is irregular or there are symptoms such as palpitations or breathlessness. Your doctor decides. (USPSTF 2021) (NICE NG196)

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