March 22, 2000 (Cleveland) -- As many as half of all first heart attack victims are thin nonsmokers with good cholesterol levels. So why do they have heart attacks? That's a question that has bedeviled heart experts for decades, but now they think they may have found a clue: a substance in the blood called C-reactive protein (CRP).
CRP is produced in the liver as part of a response to inflammation in the body. Researchers have speculated for years that inflammation in some way has a role in the development of heart disease. They also have known that CRP levels are higher in people with heart disease, but just recently they developed a new test that detects levels of "high-sensitivity CRP" in the blood. Called hs-CRP, this is the substance that now has cardiology researchers' hearts racing.
Researchers studying data collected from a study of more than 20,000 postmenopausal women say that an elevated level of hs-CRP can predict a first heart attack, and it can make that prediction even in a woman whose LDL -- or bad cholesterol -- is at 130, the recommended goal level. This, says Jonathan Abrams, MD, an expert in prevention of heart disease, is big, big news. These results may change the way heart specialists assess the risk of heart attack, he says.
One of the researchers who is studying the role of hs-CRP, Paul M. Ridker, associate professor of medicine at Harvard School of Medicine in Boston, tells WebMD that this latest study actually compared the reliability of 12 different "markers" for heart disease. Among those were cholesterol, cigarette smoking, obesity, and diabetes -- all known risk factors for heart disease. "High-sensitivity CRP was the strongest single predictor," he says. Ridker reports that the risk of heart attack was more than four times higher for women with the highest levels of hs-CRP, compared to those with the lowest levels.
Ridker says this finding means that it may be time to consider using powerful cholesterol-lowering drugs, called statins, in women with elevated hs-CRP. Some large studies of these drugs have found that they can reduce the number of heart attacks among people with only moderate elevations in cholesterol. Because elevated hs-CRP appears to increase risk even in women whose "LDL is at goal levels, it may be that initiating statin therapy could prevent first heart attack."
Abrams, who is a professor of medicine at the University of New Mexico and a leader in preventive cardiology, tells WebMD that the study is a "blockbuster." Abrams served on an American Heart Association task force that issued the latest guidelines on risk factors just two months ago, but at that time, this information wasn't published. "At the time, CRP wasn't ready for prime time, but now if it's not ready, it is definitely in the wings. This paper raises the real possibility of altering policy and guidelines. If one recommends [cholesterol] profiles on healthy adults, why not include hs-CRP?"
Another researcher not affiliated with the study, David M. Herrington, MD, MHS, tells WebMD that "the data clearly show that using hs-CRP helps identify people who are at high risk. What we don't know is whether or not these people will favorably respond to one or more forms of treatment." Herrington is associate professor of medicine at Wake Forest University School of Medicine in Winston-Salem, N.C.
William W. O'Neill, MD, director of cardiology at William Beaumont Hospital in Detroit, says the most exciting aspect of this latest report is the very real possibility that hs-CRP may finally help cardiologists identify the "30% to 50% of first heart attack victims who don't fit any of the established risk categories." But, he says, "it is still unknown if lowering [cholesterol] will lower CRP."
Herrington says there may be another use for hs-CRP testing in postmenopausal women. "Estrogen actually makes CRP go up, so if a woman already has elevated CRP it may be useful to advise her to avoid estrogen," says Herrington.
Finally, Abrams says that adding hs-CRP should not have a big economic impact. "I'm told the test only costs $20 or so," he says.
- As many as half of all first-time heart attack victims do not fit into any of the known risk categories, but researchers are finding more evidence that a form of C-reactive protein (CRP) can better predict who will have a heart attack, even in those with no other risk factors.
- CRP is produced in the liver as part of a response to inflammation, and a test for a form of the substance has been recently developed.
- Some researchers believe that patients with high levels of a form of CRP could benefit from taking cholesterol-lowering drugs, called statins, even if their cholesterol levels are normal.