Increased cardiothoracic ratio (summary)

Last revised by Jeremy Jones on 24 May 2018
This is a basic article for medical students and other non-radiologists

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

Reference article

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

  • pathophysiology
    • enlargement of the heart
      • global or specific chamber enlargement
  • role of imaging
    • identify the increased CTR
    • determine whether this represents cardiomegaly
    • look for any signs of heart failure
  • use a PA chest x-ray
  • a cardiothoracic ratio above 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
  • do NOT use an AP chest x-ray
    • the mediastinum is magnified
    • an increased cardiothoracic ratio is much less specific

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Cases and figures

  • Case 1: normal
    Drag here to reorder.
  • Case 2: increased CTR (cardiomegaly)
    Drag here to reorder.
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