Blood Test May Help Find Heart Disease

As cholesterol builds up on artery walls, it forms plaques which cause the inner lumen (opening) of the arteries to become smaller, and blood pressure goes up. Now, a new test may help predict dangerous plaque ruptures in those clogged arteries - ruptures that can lead to heart attack or stroke.

The inexpensive, easy
blood test measures circulating levels of an inflammation-linked compound called C-reactive protein (CRP), and it is becoming more commonly used nationwide.

CRP is a marker of inflammation, the process by which the body responds to injury and disease. As arteries get clogged with cholesterol and placed under increasing strain, inflammation often occurs.

"Even people with relatively low cholesterol levels, if they have a high CRP they may still be at high risk for heart trouble," says Dr. James O'Keefe, a spokesman for the American College of Cardiology (ACC) and director of preventive cardiology at the Mid-America Heart Institute in Kansas City.

New Test Complements Standard Testing

Another expert, former American Heart Association (AHA) president Dr. Sidney Smith, stresses that the CRP screen should complement - not replace - traditional diagnostic tests such as screens for cholesterol and high blood pressure.

"At this point in time, it looks as if it will provide important additive information, additional data that will be very helpful," he says.

Dr. Smith, director of cardiovascular science and medicine at the University of North Carolina at Chapel Hill, was also a co-author of AHA recommendations on CRP screening, issued in 2003.

At that time, the AHA advised "against screening of the entire adult population for [CRP]." Instead, it recommended physicians use the test at their own discretion, noting that it is probably most useful in patients already diagnosed with various risk factors for heart disease.

"It may be that CRP helps cause the inflammation, but mostly it's a marker for it," Dr. O'Keefe says. CRP is not restricted to heart disease. In fact, it is found at relatively high levels in people with chronic inflammatory illnesses such as rheumatoid arthritis or inflammatory bowel disease.

However, "We've learned over the past decade that the process of atherosclerosis [hardening of the arteries] develops over years, and that inflammation seems to be a very important part of causing the atherosclerotic lesion to ulcerate and then 'clot off,' " Dr. Smith notes.

"So it's this combination of the atherosclerotic process and the presence of an active inflammatory state that seems to identify people that are at higher risk," says Dr. Smith.

Dr. O'Keefe agrees. "I like to use the analogy of a pimple on your skin," he says. In pimples, as in diseased arteries, inflammation swells the affected tissue, often to the bursting point.

Of course, when pimples burst, the effects are mostly cosmetic and fleeting. But when plaques in the inner lining of arteries burst, "it exposes [fatty] material and sends it into the bloodstream, making the blood more likely to clot - and that's how a heart attack happens," Dr. O'Keefe explains.

That is why the CRP test - which costs about $12 - may be especially helpful for patients already at high cardiovascular risk due to factors such as high blood cholesterol, hypertension, obesity, smoking, or a family history of heart disease.

Like the AHA , the ACC has yet to designate the CRP test as a standard, first-line screen for heart disease, but Dr. O'Keefe says that "as more and more information comes out, I'm sure they will in the near future."

Elevated CRP May Predict Heart Trouble

He points to two separate articles, published this past January in the New England Journal of Medicine . Both studies found that "elevated CRP is as strong a predictor as LDL 'bad' cholesterol, in predicting who's going to get heart trouble," Dr. O'Keefe notes.

Even individuals with low cholesterol might benefit from the CRP test, Dr. O'Keefe adds.

"There's data to suggest that [patients with high CRP] can reduce their risk for heart attack by treating their already low cholesterol with a statin drug, to lower it further. Because statins also lower inflammation, as well," he says.

Most Americans may not need to turn to medications to lower arterial inflammation, however, since the very behaviors that drive up cholesterol and high blood pressure - smoking, lack of exercise, and poor diet - appear to send CRP skyward, too.

"The most important risk factor of all is obesity," Dr. O'Keefe warns. "Chronic excess weight, especially around the midsection, increases C-reactive protein. Lean people tend to have lower CRP, so my advice is to exercise more, lose weight, and eat a healthy diet."

Always consult your physician for more information.