Expansion
Runs within the pericardium from the aortic valve to the sternal angle, with the pulmonary trunk in front
Expansion
- Begins at the aortic valve, at the level of the third left costal cartilage
- Ends at the sternal angle, where it becomes the arch
- Lies entirely within the pericardium, sharing a sleeve of serous pericardium with the pulmonary trunk
Relations:
- Anteriorly and to the left - pulmonary trunk
- Posteriorly - left atrium, right pulmonary artery
- To the right - superior vena cava
- Passing behind it - the transverse sinus
The intrapericardial course is the key clinical fact. A type A aortic dissection involving the ascending aorta can rupture into the pericardial sac, producing tamponade, or extend proximally to disrupt the aortic valve and the coronary ostia, which is why it is a surgical emergency while type B dissections are often managed medically.