Increased cardiothoracic ratio (summary)

Dr Henry Knipe and Dr Jeremy Jones et al.

Increased cardiothoracic ratio describes widening of the cardiac silhouette on a chest radiograph. This is only of use when making assessment of a PA chest x-ray since the AP chest x-ray causes artefactual magnification of the heart and the cardiothoracic ratio is altered.

Reference article

This is a summary article; read more in our article on increased cardiothoracic ratio.


  • pathophysiology
    • enlargement of the heart
      • may be global or specific chamber enlargement
  • radiographic features
    • PA chest x-ray
      • a cardiothoracic ratio over 50% describes cardiomegaly
        • measure the heart at its widest point
        • measure the thorax at its widest point
        • divide the cardiac dimension by the thoracic dimension
    • AP chest x-ray
      • the mediastinum is magnified
        • increased cardiothoracic ratio is much less specific
Medical student radiology curriculum
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Article information

rID: 51429
Systems: Chest, Cardiac
Synonyms or Alternate Spellings:

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Cases and figures

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    Normal cardiothor...
    Case 1: normal
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    Cardiothoracic ra...
    Case 2: increased CTR (cardiomegaly)
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