Two new studies may help explain why many people who suffer heart attacks do not exhibit any common symptoms of cardiovascular disease. In the first study, researchers have found that patients who have high levels of an enzyme associated with blood vessel inflammation (called myeloperoxidase, MPO) have a higher risk of heart disease than those patients without high MPO levels. Similarly, the second study found that patients with high blood levels of a protein called interleukin 6 (IL-6) have a higher risk of death from advanced coronary artery disease than patients without high IL-6 levels. Though the research is still in early stages, the studies may eventually help physicians identify which patients should be treated aggressively for heart disease. Researchers may also be able to develop new drug therapies for patients to help lower their risk of heart disease.

In the first study, Renliang Zhang, MD and his colleagues from the Cleveland Clinic in Ohio compared 158 patients with established coronary artery disease and 175 patients without heart disease. The researchers measured MPO levels in the blood of the patients and found that MPO levels were significantly higher in patients with coronary artery disease.

According to co-researcher Stanley Hazen, MD, the finding is important because 50% of people that have coronary artery disease exhibit no symptoms, such as family history of the disease, high cholesterol or high blood pressure, obesity, etc. Previous research has found that MPO is associated with the production of molecules that damage arteries and contribute to heart disease, said Dr. Hazen, who is Professor of Cardiology at the Cleveland Clinic Foundation.

The researchers believe that that identifying patients with high MPO blood levels may lead to advances in heart disease treatment. For example, drugs could be developed that inhibit MPO activity and protect a patient’s arteries. However, an accompanying editorial in the Journal of the American Medical Association warns that further research is needed to better understand how MPO relates to heart disease before physicians can start testing MPO blood levels in the general population.

In a second study published in the same journal issue, researcher Eva Lindmark and her colleagues from Uppsala University Hospital in Uppsala, Sweden studied 2,369 patients with unstable coronary artery disease and high IL-6 protein levels in their blood. Half of the patients were treated aggressively with either angioplasty to widen the blood flow through the arteries or bypass surgery to create new blood routes. The other half of the patients were treated less aggressively with drug therapies or placebos (inactive pills).

The researchers found that the patients with high IL-6 protein levels who were treated aggressively were significantly less likely to die from heart disease within a year than the patients with high IL-6 levels who were not treated with angioplasty or bypass surgery. The findings suggest that measuring IL-6 blood levels can help identify which patients should be treated aggressively for heart disease. IL-6 belongs to a group of proteins called cytokines and like MPO, cytokines are associated with blood vessel inflammation.

While the research on MPO and IL-6 levels is promising, Dr. David Vorchheimer, co-author of the accompanying editorial in the Journal of the American Medical Association, stressed that people should not focus too much on early research and should not ignore established methods of preventing cardiovascular events such as heart attacks. For example, the use of a class of drugs called statins can help to significantly reduce high cholesterol, a factor associated with increased heart disease risk.

In patients who have already been diagnosed with coronary heart disease, a number of precautions can be taken to help reduce the risk of a heart attack or other serious consequence. These measures (when applicable) include: lowering cholesterol or lowering blood pressure levels with lifestyle/dietary changes or drug therapies. Angioplasty (a procedure to widen the blod flow through the arteries) or bypass surgery (a procedure to create a new route for the blood) may also be performed when necessary.

Additional Resources and References

• The study, "Association Between Myeloperoxidase Levels and Risk of Coronary Artery Disease," is published in the November 7, 2001 issue of the Journal of the American Medical Association (Vol. 286, No. 17). An abstract of the study is available at http://jama.ama-assn.org/
• The study, "Relationship Between Interleukin 6 and Mortality in Patients with Unstable Coronary Artery Disease," is published in the November 7, 2001 issue of the Journal of the American Medical Association (Vol. 286, No. 17). An abstract of the study is available at http://jama.ama-assn.org/
• To learn more about heart disease, please visit http://www.imaginis.com/heart-disease/

Return to Heart Disease News Archives