Aortic dissection is a tear in the wall of the vessel causing blood to flow between the layers of the aorta. Blood vessels have three layers of tissue starting from the inner layer that is closest to the blood and go to the outer layer. A tear can begin in the inner layer of aorta, called the intima, and the blood will fill into the next layer, called the media, and possibly the outer layer called the adventitia. There can also be a complete ruture of the aorta, where blood is spilling out into the body cavity. A dissection increase in length along the aorta. If the dissection goes in the direction of blood flow toward the iliac bifurcation, it is called an anterograde dissection. If the dissection goes against the blood and back toward the heart, it is called a retrograde dissection. There are also different classifications of aortic dissection depending upon where in the aorta the dissection occurred. An aortic dissection is a medical emergency. It can be caused by hypertension, connective tissue disorders, stenosis of the aortic valves, and chest trauma. 72 -80% of patients with an aortic dissection have a history of high blood pressure. The majority of patients will have severe stabbing chest pain with a aortic dissection. This is sometimes confused with the signs of a heart attack. Surgery is usually the solution for an acute dissection. Patient who have a dissetion and are also having high blood pressure should be given medication to keep their blood pressure under control and not further complicate the dissection.
The above picture MRI reconstruction of of the aorta and it's branches down to the kidneys. You can see the dissection in the arch.
