Aortopulmonary window also refers to a congenital cardiac defect called aortopulmonary septal defect. There is a deficiency in the septum between the aorta and pulmonary artery, resulting in a communication between the two.

The aortopulmonary window is a small space between the aortic arch

Aortic arch

The arch of the aorta or the transverse aortic arch is the part of the aorta that begins at the level of the upper border of the second sternocostal articulation of the right side, and runs at first upward, backward, and to the left in front of the trachea; it is then directed backward on the left...

 and the pulmonary artery

Pulmonary artery

The pulmonary arteries carry deoxygenated blood from the heart to the lungs. They are the only arteries that carry deoxygenated blood....

 that is visible in the lateral chest radiograph. It contains the ligamentum arteriosum

Ligamentum arteriosum

The ligamentum arteriosum is a small ligament attached to the superior surface of the pulmonary trunk and the inferior surface of the aortic arch...

, the recurrent laryngeal nerve

Recurrent laryngeal nerve

The recurrent laryngeal nerve is a branch of the vagus nerve that supplies motor function and sensation to the larynx . It travels within the endoneurium...

, lymph node

Lymph node

A lymph node is a small ball or an oval-shaped organ of the immune system, distributed widely throughout the body including the armpit and stomach/gut and linked by lymphatic vessels. Lymph nodes are garrisons of B, T, and other immune cells. Lymph nodes are found all through the body, and act as...

s, and fatty tissue. The space is bounded anteriorly by the ascending aorta

Ascending aorta

The ascending aorta is a portion of the aorta commencing at the upper part of the base of the left ventricle, on a level with the lower border of the third costal cartilage behind the left half of the sternum; it passes obliquely upward, forward, and to the right, in the direction of the heart’s...

, posteriorly by the descending aorta

Descending aorta

The descending aorta is part of the aorta, the largest artery in the body. The descending aorta is the part of the aorta beginning at the aortic arch that runs down through the chest and abdomen. The descending aorta is divided into two portions, the thoracic and abdominal, in correspondence with...

, medially by the left main bronchus

Left main bronchus

The left main bronchus is smaller in caliber but longer than the right, being nearly 5 cm long...

, and laterally by mediastinal pleura

Mediastinal pleura

Different portions of the parietal pleura have received special names which indicate their position: thus, that portion which lines the inner surfaces of the ribs and Intercostales is the costal pleura; that clothing the convex surface of the diaphragm is the diaphragmatic pleura; that which rises...

.

"Aortopulmonary window" also refers to a congenital heart defect similar in some ways to truncus arteriosus

Truncus arteriosus

Truncus arteriosus may refer to:*Persistent truncus arteriosus, a rare congenital heart disease*Truncus arteriosus , part of an embryo's developing circulatory system...

. Truncus arteriosus involves a single valve; aortopulmonary window is a septal defect.