Aortopulmonary window (radiograph)

The aortopulmonary (aortic-pulmonary or AP) window is a radiological mediastinal space seen on frontal chest x-rays.

Beware that the term aortopulmonary window can also refer to a rare form of congenital heart disease, usually referred to with the acronym APWAPW (insteadinstead ofAP AP window), where there is an opening between the aorta and the pulmonary trunk ⁴.

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

Gross anatomy

Boundaries

The AP window boundaries are ^{1, 2}:

• superior - inferior: inferior wall of the aortic arch
• inferior -: superior wall of the left pulmonary artery
• anterior -: posterior wall of the ascending aorta
• posterior -: anterior wall of the descending aorta
• medial -: trachea; lateral wall of the left main bronchus; oesophagus (anterior to posterior)
• lateral -: pleural surface of the left lung contacting the superior boundary (aortic arch) and extending to the inferior boundary (left pulmonary artery)

Contents

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

• left phrenic nerve
  • left recurrent laryngeal nerve
• left vagus nerve
• left bronchial arteries
• ligamentum arteriosum
• fat
• lymph nodes

Radiographic appearance

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}:

• mediastinal lymphadenopathy (most common ³)
• prominent mediastinal fat (normal variant ³)
• aortic or bronchial artery aneurysms
• malignancy - e.g. nerve sheath tumour