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MESA finds a better way to predict heart disease

By Patricia S. Guthrie/MESA Project Writer

Blood pressure and cholesterol are some of the numbers physicians look at when accessing a person’s risk of heart disease. But another number that measures the amount of calcium in the coronary arteries may be a better predictor. That’s one of the major findings MESA researchers learned from thousands of participants willing to be followed for the past decade in the name of improving heart health for their children and grandchildren. MESA (Multi-Ethnic Study of Atherosclerosis) is funded by the National Heart, Lung, and Blood Institute of the National Institutes of Health and is researching many aspects of heart health among four major ethnic/racial groups. Hundreds of findings from MESA studies have been published in medical journals; three of the articles are reviewed here so participants will have a better understanding of how they’re helping advance medical research. MESA’s research has also been reported in media such as Time and HealthDay News and explained in a video produced by a leading medical journal.

Healthy coronary arteries -- a healthy heart

Coronary arteries feed the muscle of the heart, which works hard pumping some five quarts of blood throughout the body every minute of every day. (Heart Facts Cleveland Clinic) Healthy arteries shouldn’t have calcium in them; it’s a sign of atherosclerosis, the narrowing and damage of the arteries that can lead to heart attacks and other heart problems. Oftentimes, a fatal heart attack is a person’s first – and last – symptom of heart disease. Nearly 70% of heart attacks and 50% of sudden deaths due to coronary artery disease occur in people who have never been diagnosed with the disease. The challenge has been to find a better way to measure a person’s risk of developing heart disease so preventative steps – such as lifestyle changes or treatment – can be taken.

Comparing heart screening methods

Heart disease is the number one killer of all Americans, no matter what race or ethnic background. In 2007, more than 406,351 Americans died from cardiovascular disease -- about one person every minute. (American Heart Association) Keeping hearts healthy means preventing problems before the damage is done. How to best assess a person’s risk of future heart troubles has challenged doctors and researchers for decades.

Framingham Risk Score

Some MESA researchers looked at whether there is a better way to predict heart disease risk than a widely used screening method, known as the Framingham Risk Score. The Framingham method evaluates people who’ve never had heart disease by using standard risk factors, such as age, blood pressure, cholesterol levels, and smoking.

Ultrasound Scans

Another screening tool uses ultrasound technology to look at the large (carotid) arteries in the neck (ARCH Intern Med 2008). Thickening of the walls of the carotid arteries, which are the main arteries that carry blood to the brain, are another indication of arterial disease.

Ultrasound device:

Calcium buildup

MESA researchers looked to see if there was an even better way to tease out a person’s risk for heart disease using a third screening method to look for calcium buildup. Participants underwent a computed tomographic (CT) scan of the chest, and researchers evaluated the amount of coronary calcium. None of the participants had a prior history of heart disease; most also underwent heart disease risk assessment using the Framingham Risk Score and arterial ultrasound scan. (NEJM March 27, 2008)

CT Scanner:

Higher scores, higher risk

Of the 6,814 participants, 162 suffered coronary events, 89 of which were major, meaning a heart attack, angina, stroke or death. Looking at all participants’ calcium scores and how they fared nearly four years later, researchers calculated a risk analysis:

• The higher the coronary calcium score, the more likely that heart disease will occur.
• Risk of coronary heart disease is 35 percent higher if a participant’s calcium score is twice that of an individual with similar risk factors.
• Participants with high calcium scores (over 300) are seven times more likely to have coronary heart disease than individuals with no detectable calcium in their arteries.
• Calcium buildup in coronary arteries predicted the likelihood of future coronary events better than ultrasound, which has become standard practice for assessing heart disease risk.

"The data from MESA and similar studies suggest that the results of the coronary artery calcium score can improve our ability to predict how likely it is that a person will develop coronary heart disease over the next several years," said Dr. Tamar S. Polonsky, a MESA researcher at Northwestern University Feinberg School of Medicine. Polonsky is also the lead author of the April 2010 paper appearing in the Journal of the American Medical Association (JAMA 2010). Polonsky explained that the calcium score method is most helpful with people who are deemed at "intermediate risk" based on other risk factors, such as blood pressure or cholesterol. "This is the group of people in which it’s not always clear whether they need to start medication to lower their cholesterol or whether it’s appropriate to focus on diet and exercise," she said. "Looking at the coronary artery calcium score put many of the intermediate risk people in the high or low risk group, where the treatment decisions are more clear."

However, Polonsky cautioned that the coronary artery calcium score "is not for everyone". It’s much less helpful in people already categorized at low or high risk, she said, because the score "rarely changed how we thought about their risk." If the information gained from a CT scan looking at calcium buildup isn’t likely to change a person’s current treatment plan, then "it’s probably not worth getting," she said. But as always, people need to discuss their concerns with their own doctor.

The ultimate contribution

Could MESA’s findings lead to coronary arterial calcium scores becoming the new standard for assessing heart disease? Physicians and their organizations, such as the American Heart Association, continue to debate these merits. Decades from now, MESA’s participants and researchers could be remembered for their ultimate contribution – providing evidence that helped reduce the risk of Americans dying from heart disease.

SOURCES

Study: Calcium Helps Predict Heart Attack Risk
http://www.time.com/time/health/article/0,8599,1985311,00.html

Arterial Calcium Scans Can Predict Death Risk
http://health.usnews.com/health-news/family-health/articles/2008/06/23/arterial-calcium-scans-can-predict-death-risk

Video: Coronary Artery Calcium Score Aids Physicians in Better Classifying Heart Disease Risks
http://jama.ama-assn.org/content/303/16/1610/suppl/DC1

American Heart Association/CDC; 2011report
http://networking.americanheart.org/blogs/6/114

Cleveland Clinic “Your Heart and Blood Vessels
http://my.clevelandclinic.org/heart/heart-blood-vessels/heart-facts.aspx

NHLBI National Cholesterol Education Program
http://hp2010.nhlbihin.net/atpiii/calculator.asp

What is Atherosclerosis?
http://www.nhlbi.nih.gov/health/health-topics/topics/atherosclerosis/

AHA Finally Endorses Calcium Scores
http://heartdisease.about.com/od/coronaryarterydisease/a/AHAcalcium.htm

JAMA Letters to Editor about MESA findings
http://jama.ama-assn.org/content/304/7/741.1.full

Your Risk of Heart Disease: How to turn back the clock when your blood vessels grow old before you
http://online.wsj.com/article/SB10001424052748703406604575278713597433300.html#

The Framingham method evaluates http://cvdrisk.nhlbi.nih.gov/calculator.asp

MEDICAL JOURNAL ARTICLES published by MESA researchers:

Detrano R, Guerci AD, Carr JJ, Bild DE, Burke G, Folsom AR, Liu K, Shea S, Szklo M, Bluemke DA, O’Leary DH, Tracy R, Watson K, Wong ND, Kronmal RA. Coronary Calcium as a Predictor of Coronary Events in Four Racial or Ethnic Groups. N Engl J Med. 2008;358(13):1336-1345.

Folsom AR, Kronmal RA, Detrano RC, O’Leary DH, Bild DE, Bluemke DA, Budoff MJ, Liu K, Shea S, Szklo M, Tracy RP, Watson KE, Burke GL. Coronary Artery Calcification Compared With Carotid Intima-Media Thickness in Prediction of Cardiovascular Disease Incidence: The Multi-Ethnic Study of Atherosclerosis (MESA). Arch Intern Med. 2008;168(12):1333-1339.

Polonsky TS, McClelland RL, Jorgensen NW, Bild DE, Burke GL, Guerci AD, Greenland P. Coronary Artery Calcium Score and Risk Classification for Coronary Heart Disease Prediction. JAMA 2010;303(16):1610-1616.