Heart News
Reviewed by Dr. Stanley Hazen M.D., Ph.D., Section Head of Preventive Cardiology at the Cleveland Clinic Heart & Vascular Institute
Rev. 4/06.
The first heart disease indicator to be recommended by the American Heart Association in twenty years entails only a surprisingly simple, inexpensive blood test. This high sensitivity C-reactive protein (hs-CRP) test takes the traditional cardiac check-up a step further, pinpointing those people who are at a much higher risk than others for heart disease, America’s leading cause of death. From hs-CRP results, doctors gain crucial insight into inflammation of the blood vessels around the heart, a factor not considered until now for patients at risk.
Q: What is C-reactive protein? How does it relate to heart disease?
A: The body produces C-reactive protein (CRP) during the general process of inflammation. When a disease called atherosclerosis damages arteries around the heart, they become inflamed, which triggers CRP production. For years we thought that diseased arteries around the heart slowly narrow, then clog or collapse and cause a heart attack. While this does occur, it is much more rare than had been anticipated. And that theory didn’t explain the patients who were fine one day, but had a heart attack the next week. We have since found that in some people inflamed, softened artery walls develop weak areas that can rupture suddenly, causing a heart attack. Also, plaque can build up quickly in inflamed arteries, increasing the risk of blood clots.
THE INFLAMED VESSEL In the blood vessel above, cholesterol buildup is present (yellow); but that’s not the only heart disease risk factor pictured. Doctors are also turning their attention to the diseased area of the vessel marked by inflammation (dark red and white).
Q: How do doctors test for CRP?
A: Physicians measure CRP with a simple, convenient blood test that does not require fasting. General CRP blood testing has been around for years, but only one kind, the high-sensitivity C-reactive protein (hs-CRP) test, helps determine heart disease risk. Patients should ask their doctors about hs-CRP specifically. With hs-CRP test results, a level above three raises major concern because it means a person’s risk for heart attack is at least doubled. One to three merits some concern, but is not serious. Below one is where we want all patients. Readings of 50 and above are possible, but we generally attribute a level higher than 10 to an infection or other source of inflammation somewhere in the body, not arterial inflammation.
Q: How does the hs-CRP test compare to other indicators, such as cholesterol and stress tests?
A: The exercise stress test tells us when narrowed arteries cause a shortage of blood going to the heart. It is still a vital risk indicator. LDL cholesterol is important to watch because it can narrow and clog arteries. There are two types of LDL cholesterol, the bad kind and the really bad kind, which we call oxidized LDL cholesterol. The available cholesterol test does not differentiate between these two types; it only tells a person’s total LDL level. However, this bad, oxidized type, which hurts the arteries and speeds up plaque formation, has a direct correlation to CRP levels. Arteries can produce CRP directly at sites where there is cholesterol buildup. So, hs-CRP testing offers a window into how much of the especially bad cholesterol a person has in his or her blood.
Q: How do people know if they need an hs-CRP test?
A: People who have suffered a heart attack or stroke and those with at least one risk factor, such as family history, high blood pressure, high cholesterol, smoking or diabetes, should be tested. While the American Heart Association and Centers for Disease Control just recently recommended hs-CRP testing as an option for those already at risk, The Cleveland Clinic has used the hs-CRP test routinely for at-risk patients for several years. Hs-CRP is a great test for people with one or two risk factors who wonder if they are really in jeopardy of a heart attack or a stroke. It’s probably less useful for people without any risk factors.
Q: How often should CRP levels be tested?
A: There’s no cookbook solution. If someone comes in high and then works on lowering their CRP levels, I might re-check it in a month or two. But, if the initial level is low, I may not check it again for two-to-five years. It really depends on the patient and adoption of lifestyle changes or other treatments.
Q: Is arterial inflammation the only cause of high CRP?
A: Inflammation in the body due, for instance, to infection or a serious arthritic flare, can raise CRP. Before getting an hs- CRP test, patients should tell their doctors if they are experiencing health problems that can cause general inflammation, for example, joint problems or a respiratory infection. If tested while ill or injured, and hs-CRP comes back elevated, it’s important to get re-tested once healthy. But, pinpointing an alternative reason for a high hs-CRP reading doesn’t eliminate the increased risk for heart disease or the value of the hs-CRP test. Inflammation anywhere in the body makes the arteries vulnerable because the cells and substances in the body that drive inflammation are thrown into high gear. Inflammation itself fuels further inflammation.
Q: What can I do if my hs-CRP level is high?
A: Inflammation should be treated by lifestyle change, such as losing weight, exercising, controlling diabetes, stopping smoking, controlling high blood pressure, and reducing alcohol intake. Antithrombotic medications such as aspirin or clopidogrel may provide protection. Cholesterol-lowering statin drugs and ACE inhibitors may also reduce CRP. Your doctor will prescribe the correct medications and dosage to treat your condition.
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