Aortic Dissection: Catastrophe for the Aorta

Aortic dissection is the most common catastrophe affecting the aorta, which is the large artery through which blood leaves the heart to deliver oxygenated blood to the rest of the body. It occurs in about 24 people per million each year in the U.S. It is caused when the inner layer of the aortic wall tears and then peels or separates away from the next layer of the aorta. This creates two channels; the original aortic channel for blood flow (the true lumen) is still present while the peeling away of the outer layer in the dissection creates a new additional aortic flow channel (the false lumen).

This double-barrel flow pattern in the dissected aorta can cause serious problems downstream. The dissection or separation can result in a significant decrease in blood flow to various organs and tissues supplied by the involved branches. Branches that may be affected include the kidney (renal) arteries, the gut (mesenteric) arteries, leg arteries, and others.

The main risk factor for an aortic dissection is a history of high blood pressure (hypertension). Over time, hypertension weakens the aortic wall, making it more likely to have a spontaneous tear involving the inner lining of the aorta. The tear exposes the middle of the wall to aortic blood pressure. This creates a separation that unzips the aorta between the layers which are pulled apart by the dissection process. As the dissection progresses through the aorta, it may extend into critical aortic branches, causing poor blood flow to various organs. The result of this may be kidney failure or death of the intestines, increased risk of stroke, leg pain, and death.

In all cases, the first treatment for patients with aortic dissection is aggressive control of blood pressure with medications. In some patients, the exact type of aortic dissection, including how much of the aorta is involved, the effects of the dissection on various parts of the body, and the resulting symptoms, may require additional therapy to prevent or manage complications. This may include a surgical repair to replace the site of the initial tear.

In cases where surgery is not advised, the risk of death within the first 30 days after an aortic dissection occurs is in the range of 10% to 17%. There is a tendency for the aortic false lumen to grow over time. This expansion may progress to an aneurysm (an abnormally enlarged size, usually greater than twice the normal vessel diameter) with an increased risk of rupture. This degree of aortic enlargement occurs in about one third of patients within two years after the diagnosis of aortic dissection and continues to carry significant risk, requiring close monitoring.

Patients who have medical management of their symptoms must be followed regularly by their physician. Blood pressure must be controlled at all times. If surgery is performed, patients must still keep their blood pressure within normal levels and be seen regularly by their health-care provider.

About the Author: Michael D. Dake, MD, is Professor of Radiology and Internal Medicine at the University of Virginia School of Medicine and Chairman, Department of Radiology at the University of Virginia Health System. He has published numerous articles and is a noted national speaker.