The Aorta

The aorta is the major artery, or high-pressure blood vessel, in the human body. As an artery, it carries oxygen-rich blood from the heart to the body. It starts at the top of the heart at the aortic valve and initially travels upward toward the head. It then curves downward, forming the aortic arch. Several major arteries branch off from the aortic arch. These arteries supply blood to the upper body including torso, arms, neck, and head. Then, it travels towards the feet, passing through the diaphragm into the abdomen. In the abdomen, major arteries branch off to supply the liver (hepatic artery), intestines (mesenteric arteries), and the kidneys (renal arteries). Then the aorta forms two branches, the femoral arteries, that supply the legs and feet.

Like all arteries, the wall of the aorta is elastic, expanding and contracting with each heartbeat. In some people, over time the inner lining of the aorta, or the endothelium, may stiffen and thicken. This may tear, which allows blood under pressure into the intima, or inner wall of the aorta. This may cause the outer wall to expand, forming an aneurysm. If the aneurysm forms in the abdomen, it is known as an abdominal aortic aneurysm, or AAA. Most patients with an AAA have no symptoms, and while an AAA may be felt as a pulsating mass in a thin person, it is undetectable in most. While AAAs typically take years to form, they may sometimes expand quickly and burst. A ruptured AAA is a life-threatening event requiring rapid diagnosis and treatment. Even with today’s modern medical capabilities, a ruptured AAA is often not survivable. So, the key to addressing AAAs is to diagnose and treat them before they rupture.

Risk factors for AAA include male sex, older age (average age at diagnosis is 65 to 75 years), cigarette smoking (80% of patients with AAA have a smoking history), presence of aneurysms in other blood vessels in the body, family history of AAA, high blood pressure, high cholesterol, and peripheral arterial disease. Smoking cessation and control of blood pressure and cholesterol decrease risk. Both the U.S. Preventive Services Task Force and the Society of Vascular Surgeons recommend that men aged 65 to 75, who are current or former smokers, have an abdominal ultrasound to screen for AAA. In this group, about 5% of screenings are positive. Sometimes, an AAA is detected on CT screening of the abdomen when the test is done for other reasons (this is called an incidental finding).

Management of AAA depends on its size, location, and rate of growth. Typically, smaller AAAs are monitored with ultrasound or CT over time to ensure that they are not growing. AAAs that enlarge to 55 mm in diameter in men and 50 mm in women or are rapidly increasing in size (>5 mm in 6 months or >10 mm in one year) have an increased risk of rupture and are usually referred to a vascular surgeon for repair. Repair can be either an endovascular aortic repair (EVAR) which uses catheters, or an open surgical repair, which replaces the aneurysm with a graft. Those who undergo EVAR typically recover faster, but long-term survival is about the same for both treatments.

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