Aortopulmonary window (radiograph)

Dr Henry Knipe et al.

The aortopulmonary (aortic-pulmonary or AP) window (also known as APW, but see 'Terminology' below) is a radiological mediastinal space seen on frontal chest radiographs.

The term should also not be confused with an aortopulmonary septal defect, which is occasionally also called an aortopulmonary window, referring to a rare form of congenital heart disease where there is an opening between the aorta and the pulmonary trunk 4. It is usually referred to with the acronym APW instead of AP window.

Also, be careful not to confuse the AP window with the aortic-pulmonary stripe

The AP window boundaries are 1,2:

A variety of structures traverse the AP window 1-3:

The AP window normally has a concave lateral border. A straight lateral border can be considered normal if unchanged from the previous chest x-ray. A newly straightened or convex lateral border is considered abnormal and has a number of causes 1,2:


Article information

rID: 23507
System: Chest
Synonyms or Alternate Spellings:
  • Aortopulmonary window (APW)
  • Aortic-pulmonary window
  • AP window

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Cases and figures

  • Case 1: convex AP window from lymphadenopathy
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  • Case 2: loss of AP window to pleural tumor
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