Blood test may show risk of heart attack

A previously obscure and rarely performed blood test appears to be as powerful as cholesterol measurements in estimating a person's risk of having a heart attack or stroke, according to new research.

The test measures levels of C-reactive protein (CRP), produced by the body as part of the process of inflammation. Elevated concentrations of CRP appear to identify individuals at increased risk of cardiovascular disease even when their cholesterol levels are normal.

The research, published in today's New England Journal of Medicine, is the strongest evidence to date supporting the emerging theory that inflammation plays a crucial role in determining whether or when a heart attack or stroke occurs.

Although the precise role CRP plays is unknown, it is a reliable marker for the presence and intensity of an inflammatory process.

"The implications are very big for detection and prevention" of cardiovascular disease, said Paul Ridker, a cardiologist at Harvard Medical School.

In practical terms, the new findings are likely to launch a debate about whether — or how soon — routine CRP measurement should become a part of the complex calculation of a heart attack risk that now goes on in thousands of doctors' offices every day.

In addition to varying naturally among individuals, bloodstream CRP levels are elevated in smokers, diabetics and people who are overweight. It can be reduced in a variety of ways, including with exercise and weight loss, and by taking certain drugs, including the cholesterol-lowering medicines known as statins. Some experts believe the test may provide a rough "global summary" of a person's cardiovascular risk

"I look at it today as more important than LDL," said Eric Topol, head of cardiology at the Cleveland Clinic, referring to low-density lipoprotein, the so-called "bad cholesterol." "I'm not turning my back on LDL, but if I was allowed only one test, I would use CRP," said Topol, one of the country's leading heart researchers.

Others, however, think enough questions remain unanswered — particularly the issue of whether CRP-lowering interventions are helpful — to keep it out of workaday medicine for the time being.

"It's a very exciting area for research ... but at present I don't think it should be part of clinical practice," said Daniel Levy, director of the Framingham Heart Study, the 54-year-old research project that's been the main wellspring of insight into risk factors for heart disease.

Biologists have known since the 1950s that virtually everyone develops thickened, cholesterol-filled patches in some of their arteries, starting in early adulthood. Heart attacks and strokes occur when one of those "plaques" breaks open, causing a blood clot to form and blocking the flow of blood and delivery of oxygen. If the obstruction isn't quickly cleared, the tissue downstream — heart muscle or brain cells — dies.

Research in the past decade suggests that inflammation — the complicated marshalling of immune-system cells and chemicals at the site of an injury tends to make plaques unstable. It appears that people with elevated CRP either have plaques that are more inflamed, or have a jumpier inflammatory response that makes their plaques more prone to rupture.

In the new research, Ridker and his colleagues at Brigham and Women's Hospital, in Boston, studied about 28,000 women ages 45 or older participating in the Women's Health Study. During an eight-year period, those whose CRP levels were in the top 20 percent for the entire group had 4.5 times the risk of suffering a heart attack or stroke as those in the bottom 20 percent. For LDL cholesterol, the risk to people in the top bracket was 2.2 times that of people in the bottom.