Understanding Abdominal Aortic Aneurysms
September 19, 2012
By Harvey B. Simon, M.D.
For your father, the initials AAA may represent his favorite auto club. But for your doctor, the initials stand for an abdominal aortic aneurysm. It is a widening of the body's largest artery, the aorta.
Doctors often refer to AAAs as time bombs. They are often entirely silent. There are usually no symptoms until they burst with a big bang.
Seventy-five percent of victims die before they even get to the operating room. And only about half of people survive surgery. All in all, AAAs kill over 9,000 Americans a year mostly men.
But even if AAAs are time bombs, they usually have long fuses. Doctors can detect them long before they explode.
Anyone can develop an AAA, but several factors increase risk:
New research links AAAs with high total cholesterol and low HDL ("good") cholesterol levels. Surprisingly, perhaps, diabetes is not an AAA risk factor, although it is an important risk factor for other cardiovascular diseases.
These same factors increase the risk for atherosclerosis ("hardening of the arteries"). Indeed, many people with AAAs also have atherosclerosis of other arteries, especially in their heart and legs. More than a third of patients with AAAs also have heart disease. This makes surgical repair tricky.
As an aneurysm gets bigger it can produce pain in the abdomen or back. It may feel like a pulsating sensation or gnawing ache deep in the abdomen or in the mid-back.
When an AAA breaks, it causes severe abdominal and low back pain, a sharp fall in blood pressure and collapse. Most people die.
The simplest way for a doctor to detect an AAA is to feel a pulsating swelling in his patient's abdomen, often just to the left of the belly button. Unfortunately, however, a doctor's physical exam will miss most AAAs except in thin people with sizable aneurysms. An X-ray is not much help either. Few AAAs have enough calcium in their walls to show up on an X-ray.
Ultrasound will detect 95% of all AAAs. It's simple, relatively inexpensive and an entirely safe test. And it's rare for the test to miss an AAA large enough to cause trouble.
Newer tests, such as computed tomography angiography (CTA) and magnetic resonance angiography (MRA), are also very accurate, but they are much more expensive and time-consuming than ultrasounds. Most doctors reserve CTAs and MRAs for pre-surgery evaluations; patients get an injection of dye for these tests.
If ultrasounds are so accurate and AAAs so worrisome, shouldn't everyone have the test as part of an annual physical? Most experts recommend a screening ultrasound for men at age 65 to 75. Some experts also suggest screening for men and women with a strong family history of the problem. Needless to say, anyone with symptoms that suggest an AAA should have an ultrasound as soon as possible.
AAAs make doctors and patients very nervous. It's understandable for a man to want his AAA repaired before it ruptures, but it's not that simple. Surgery is difficult and risky, even when the aneurysm is intact and stable.
The good news is that doctors can now identify the AAAs at highest risk of rupturing. The key factor is size. As an AAA gets larger, its walls get thinner and weaker, much as a balloon thins out as it's inflated.
And even though small aneurysms carry some risk of rupture, research shows that repairing aneurysms smaller than 5.5 cm (2.2 inches) does not improve survival. But even if small AAAs don't call for repair, they certainly require attention.
AAAs rupture because their walls are thin and weak. Immediate surgery is the only treatment for a ruptured aneurysm. But even with prompt diagnosis and expert surgery, only about half the patients survive. To prevent a disastrous rupture, doctors can place a graft inside the aneurysm. This helps support its walls.
There are two ways to do this:
Which type of repair is best? There's no simple answer. In the first weeks and months after AAA repair, endovascular stent graft is the winner.
By two years, however, the overall survival for the two procedures is similar. And over time patients with endovascular stent grafts are more likely to need repeat procedures than patients with surgical grafts.
Until new research is completed, the choice between surgical and endovascular AAA repair will depend on the patient's overall health and preferences and on the experience and skill of his medical team.
Prevention is the best medicine. Men can reduce their chances of getting an AAA. And they can help prevent a small AAA from growing enough to need repair or to risk a life-threatening rupture.
Harvey B. Simon, M.D., is an Associate Professor of Medicine at Harvard Medical School and a member of the Health Sciences Technology Faculty at Massachusetts Institute of Technology. He is the founding editor of the Harvard Men's Health Watch newsletter and author of six consumer health books, including The Harvard Medical School Guide to Men's Health (Simon and Schuster, 2002) and The No Sweat Exercise Plan, Lose Weight, Get Healthy and Live Longer (McGraw-Hill, 2006). Dr. Simon practices at the Massachusetts General Hospital; he received the London Prize for Excellence in Teaching from Harvard and MIT.