Aortic Dissection
Medical Author: Benjamin C. Wedro, MD, FAAEM
Medical Editor: Melissa Conrad Stöppler, MD
Introduction to aortic dissection
The aorta is the large blood vessel that leads from the heart and carries
blood to the rest of the body. The aorta originates at the aortic valve at the
outlet of the left ventricle of the heart. It ascends in the chest to an arch
where blood vessels branch off to supply blood flow to the arms and head. It
then begins to descend through the chest and into the abdomen, where it splits
into two iliac arteries that provide blood flow to the legs. Along its descent,
more small arteries branch out to supply blood to the stomach, intestine, colon,
kidneys, and the spinal cord.
The aorta has a thick wall, with three layers of muscle that allow the blood
vessel to withstand the high pressure that is generated when the heart pumps
blood to the body. The three layers are the tunica intima, tunica media, and the
tunic adventitia. The intima is the inside layer that is in contact with the
blood, the media is in the middle, and the adventitia is the outermost layer.
In an aortic dissection, a small tear occurs in the tunica intima (the
inside layer of the aortic wall in contact with blood). Blood can enter this
tear and cause the intima layer to strip away from the media layer, in effect
dividing the muscle layers of the aortic wall and forming a false channel, or
lumen. This channel may be short or may extend the full length of the aorta. A
distal (further along the course of the aorta than the initial tear) tear in the
intima layer can let blood re-enter the true lumen of the aorta.
In some cases the dissection will cross all three layers of the aortic wall
and cause immediate rupture. In most other cases the blood is contained between
the wall layers.
Picture of Aortic Dissection
While there have been different classifications historically, the Stanford
classification is most commonly used to classify aortic dissection.
- Type A dissections involve the ascending aorta and arch
- Type B involves the descending aorta.
A patient can have a combination of both.
Some patients may experience an aortic dissection without pain, and it may be
found incidentally on imaging studies performed for other purposes.
Next: What are the causes of aortic dissection? »
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