Biatrial Enlargement

Attention! Before reading this page, check out our introduction to the P wave for an explanation of the basics of atrial enlargement.


Biatrial enlargement is diagnosed when criteria for both right and left atrial enlargement are present on the same ECG.

The spectrum of P-wave changes in leads II and V1 with right, left and bi-atrial enlargement is summarised in the following diagram:

Reproduced from Wagner et al. (2007)

Electrocardiographic Criteria

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.

In lead II

Bifid P wave with:

Amplitude ≥  2.5mm


Duration  ≥ 120 ms

In V1

Biphasic P waves with:

Initial positive deflection  ≥ 1.5mm tall


Terminal negative deflection ≥ 1mm deep


Terminal negative deflection ≥ 40 ms duration

Combination criteria 

P wave positive deflection  ≥ 1.5 mm in leads V1 or V2


Notched P waves with duration >120 ms in limb leads, V5 or V6


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)

 Example ECGs

Example 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 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).

Related Topics

Further Reading

Author Credits


  • Chung DC, Nelson HM. ECG – A Pictorial Primer [internet]. Accessed 12/12/2011.
  • Edhouse J, Thakur RK, Khalil JM. ABC of clinical electrocardiography. Conditions affecting the left side of the heart. BMJ. 2002 May 25;324(7348):1264-7. Review. PubMed PMID: 12028984; PubMed Central PMCID: PMC1123219 [Full Text].
  • Harrigan RA, Jones K. ABC of clinical electrocardiography. Conditions affecting the right side of the heart. BMJ. 2002 May 18;324(7347):1201-4. Review. PubMed PMID: 12016190; PubMed Central PMCID: PMC1123164 [Full Text].
  • Jenkins RD, Gerred SJ. ECGs by Example. Second Edition. Elsevier Churchill Livingstone 2005.
  • Surawicz B, Knilans TK. Chou’s Electrocardiography in Clinical Practice. 6th Edition. Saunders Elsevier 2008.
  • Wagner, GS. Marriott’s Practical Electrocardiography (11th edition), Lippincott Williams & Wilkins 2007.

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