Biatrial Enlargement

To best understand ECG features of biatrial enlargement, it is recommended that you first review ECG changes seen in left atrial enlargement and right atrial enlargement.

Biatrial Enlargement Definition
  • Biatrial enlargement is diagnosed when criteria for both right and left atrial enlargement are present on the same ECG.
  • The diagnosis of biatrial enlargement requires criteria for LAE and RAE to be met in either lead II, lead V1 or a combination of leads

ECG Criteria for Biatrial Enlargement

The spectrum of P-wave changes in leads II and V1 with right, left, and biatrial enlargement is summarised below:

In lead II

Bifid P wave with

  • Amplitude ≥ 2.5mm AND
  • Duration ≥ 120 ms
In V1/V2

Biphasic P waves with

  • Initial positive deflection ≥ 1.5mm tall AND
  • Terminal negative deflection ≥ 1mm deep AND
  • Terminal negative deflection ≥ 40 ms duration
Combination criteria
  • P wave positive deflection ≥ 1.5 mm in leads V1 or V2 AND
  • Notched P waves with duration >120 ms in limb leads, V5 or V6

P wave changes with Biatrial Enlargement
P wave morphology LAE RAE BAE Wagner 2007

Causes of Biatrial Enlargement

Combination of both left and right atrial enlargement.

Right atrial enlargement

  • Pulmonary hypertension due to:
  • Chronic lung disease (cor pulmonale)
  • Tricuspid stenosis
  • Congenital heart disease (pulmonary stenosis, Tetralogy of Fallot)
  • Primary pulmonary hypertension

Left Atrial Enlargement

  • Mitral valve disease
  • Aortic valve disease
  • Hypertension
  • Aortic stenosis
  • Mitral incompetence
  • Hypertrophic cardiomyopathy (HOCM)

ECG Examples

Example 1
Biatrial enlargement ECG LITFL

Biatrial enlargement:

  • Lead II: Bifid P wave with Amplitude ≥ 2.5mm AND Duration ≥ 120 ms
  • P wave positive deflection ≥ 1.5 mm in lead V2
  • Leads V5 and V6: Notched P waves with duration >120 ms in limb leads

Example 2
ECG biatrial enlargement 1

Biatrial enlargement due to idiopathic cardiomyopathy:

  • Biphasic P waves in V1 with a very tall positive deflection (almost 3 mm in height!) and a negative deflection that is both deep (> 1 mm) and wide (> 40 ms).

Example 3

ECG biatrial enlargement 2

Biatrial enlargement:

  • P waves in lead II are tall (> 2.5mm) and wide (> 120 ms).
  • P waves in V2 are tall (> 1.5 mm), while the terminal negative portion of V1 is deep (> 1mm) and wide (> 40 ms).


Advanced Reading



LITFL Further Reading


MBBS (UWA) CCPU (RCE, Biliary, DVT, E-FAST, AAA) Adult/Paediatric Emergency Medicine Advanced Trainee in Melbourne, Australia. Special interests in diagnostic and procedural ultrasound, medical education, and ECG interpretation. Editor-in-chief of the LITFL ECG Library. Twitter: @rob_buttner

Emergency Physician in Prehospital and Retrieval Medicine in Sydney, Australia. He has a passion for ECG interpretation and medical education | ECG Library |

One comment

  1. I need to thank you for the ECG Library. It’s helping me a lot! I’m from Brazil, still on my way through med school. And at every cardiology class, I feel stupid looking at the ECGs and listening to the teacher. He talks as if we students understand ECG, but we don’t. And now I get it. It’s a huuuge subject, and a difficult one to explain. So… Just wanted to say thanks, because these posts have been really helpful to me, and the links and references… amazing! Now I’m actually learning ECG!

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