Right atrial enlargement

Dr David Carroll and Radswiki et al.

Right atrial enlargement is less common, and harder to delineate on chest radiograph, than left atrial enlargement.

Enlargement of the right atrium can result from a number of conditions, including:

  • amplitude of P wave in lead II > 2.5 mm
    • often demonstrate "peaked" morphology
  • initial positive deflection of P wave in lead V1 > 1.5 mm

On a frontal view, the right atrium is visible because of its interface with the right middle lobe. Subtle and moderate right atrial enlargement is not accurately determined on plain films because there is normal variability in the shape of the right atrium. Features are non-specific but include 2, 3:

  • enlarged, globular heart
  • narrow vascular pedicle
  • gross enlargement of the right atrial shadow, i.e. increased convexity in the lower half of the right cardiac border
    • right atrial convexity is more than 50% of the cardiovascular height
    • right atrial margin is more than 5.5 cm from the midline

There are no accepted standard reference measurements, and enlargement is usually determined qualitatively on CT or MRI. RA volume is not routinely recorded on echocardiography. Suggested measurements include 5:

  • right atrial normal size (measured at end systole on four chamber view)
    • long axis: 3.4-5.3 cm
    • short axis: 2.6-4.4 cm
    • area: 10-18 cm2
      • echocardiography estimates tend to be larger than on CT or MRI
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Article information

rID: 12941
System: Cardiac
Section: Gamuts
Synonyms or Alternate Spellings:
  • Enlargement of the right atrium
  • Right atrium enlargement

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Cases and figures

  • Figure 1: normal PA cardiomediastinal outlines
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  • Figure 2: diagram
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  • Figure 3: diagram
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  • Case 1: plain radiograph
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  • Case 1: CT
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  • Case 2: plain radiograph
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  • Case 2: MRI
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