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Inflammation, Heart Disease and Stroke: The Role of C-Reactive Protein How does inflammation relate to heart disease and stroke risk? “Inflammation” is the process by which the body responds to injury or an infection. Laboratory evidence and findings from clinical and population studies suggest that inflammation is important in atherosclerosis (ath”er-o-skleh-RO’sis). This is the process in which fatty deposits build up in the inner lining of arteries. C-reactive protein (CRP) is one of the acute phase proteins that increase during systemic inflammation. It’s been suggested that testing CRP levels in the blood may be an additional way to assess cardiovascular disease risk. A more sensitive CRP test, called a highly sensitive C-reactive protein (hs-CRP) assay, is available to determine heart disease risk. The American Heart Association and the Centers for Disease Control and Prevention published a joint scientific statement in 2003 on the use of inflammatory markers in clinical and public health practice. This statement was developed after systematically reviewing the evidence of association between inflammatory markers (mainly CRP) and coronary heart disease and stroke. What’s the role of CRP in predicting recurrent cardiovascular and stroke events? A growing number of studies have examined whether hs-CRP can predict recurrent cardiovascular disease, stroke and death in different settings. High levels of hs-CRP consistently predict recurrent coronary events in patients with unstable angina and acute myocardial infarction (heart attack). Higher hs-CRP levels also are associated with lower survival rates in these patients. Many studies have suggested that after adjusting for other prognostic factors, hs-CRP is useful as a risk predictor. Studies also suggest that higher levels of hs-CRP may increase the risk that an artery will reclose after it’s been opened by balloon angioplasty. High levels of hs-CRP in the blood also seem to predict prognosis and recurrent events in patients with stroke or peripheral arterial disease. What’s the role of hs-CRP in predicting new cardiovascular events? Scientific studies have found that the higher the hs-CRP levels, the higher the risk of having a heart attack. In fact, the risk for heart attack in people in the upper third of hs-CRP levels has been determined to be twice that of those whose hs-CRP level is in the lower third. These prospective studies include men, women and the elderly. Studies have also found an association between sudden cardiac death, peripheral arterial disease and hs-CRP. However not all of the established cardiovascular risk factors were controlled for when the association was examined. The true independent association between hs-CRP and new cardiovascular events hasn’t yet been established. What causes low-grade inflammation? The major injurious factors that promote atherogenesis — cigarette smoking, hypertension, atherogenic lipoproteins, and hyperglycemia — are well established. These risk factors give rise to a variety of noxious stimuli that cause the release of chemicals and the activation of cells involved in the inflammatory process. These events are thought to contribute not only to the formation of plaque but may also contribute to its disruption resulting in the formation of a blood clot. Thus, virtually every step in atherogenesis is believed to involve substances involved in the inflammatory response and cells that are characteristic of inflammation. In addition, there is also research that indicates an infection — possibly one caused by a bacteria or a virus — might contribute to or even cause atherosclerosis. The infectious bacteria, Chlamydia pneumoniae (klah-MID'e-ah nu-MO'ne-i), has been shown to have a significant association to atherosclerotic plaque. The herpes simplex virus has also been proposed as an initial inflammatory infectious agent in atherosclerosis. The notion that chronic infection can lead to unsuspected disease isn't foreign to most doctors. For example, bacterial infection with Helicobacter pylori is now known to be the major cause of stomach ulcers. The treatment for this condition now routinely includes antibiotic therapy. Should I have my CRP level measured? If a person’s cardiovascular risk score — judged by global risk assessment — is low (the possibility of developing cardiovascular disease is less than 10 percent in 10 years), no test is immediately warranted. If the risk score is in the intermediate range (10–20 percent in 10 years), such a test can help predict a cardiovascular or stroke event and help direct further evaluation and therapy. However, the benefits of such therapy based on this strategy remain uncertain. A person with a high risk score (greater than 20 percent in 10 years) or established heart disease or stroke should be treated intensively regardless of hs-CRP levels. What is the normal range of hs-CRP level?
If, after repeated testing, patients have persistently unexplained, markedly elevated hs-CRP (greater than 10.0 mg/L), they should be evaluated to exclude noncardiovascular causes. Patients with autoimmune diseases or cancer, as well as other infectious diseases, may also have elevated CRP levels. Related AHA publications/Web content:
Related AHA Scientific Statements: See also: Aspirin in Heart Attack and Stroke Prevention Atherosclerosis Fat Heart Attack High Blood Pressure J-Curve Phenomenon Prevention, Primary Prevention, Secondary Risk Factors and Coronary Heart Disease Thrombolysis, Thrombosis, Thrombus and Embolus |
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