Aortopulmonary window (radiograph)
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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 - unfortunately - 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:
- superior: 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; esophagus (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)
A variety of structures traverse the AP window 1-3:
- left phrenic nerve
- left vagus nerve
- left recurrent laryngeal nerve
- left bronchial arteries
- ligamentum arteriosum
- lymph nodes
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:
- 1. Gibbs JM, Chandrasekhar CA, Ferguson EC et-al. Lines and stripes: where did they go?-From conventional radiography to CT. Radiographics. 2007;27 (1): 33-48. Radiographics (full text) - doi:10.1148/rg.271065073 - Pubmed citation
- 2. Marano R, Liguori C, Savino G et-al. Cardiac silhouette findings and mediastinal lines and stripes: radiograph and CT scan correlation. Chest. 01;139 (5): 1186-96. doi:10.1378/chest.10-0660 - Pubmed citation
- 3. Whitten CR, Khan S, Munneke GJ et-al. A diagnostic approach to mediastinal abnormalities. Radiographics. 2007;27 (3): 657-71. Radiographics (full text) - doi:10.1148/rg.273065136 - Pubmed citation
- 4. Ghaderian M. Aortopulmonary window in infants. Heart Views. 2012;13 (3): 103-6. Heart Views (full text) - doi:10.4103/1995-705X.102153 - Free text at pubmed - Pubmed citation