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How Well Do CAC Scores Predict Heart Attack Risk?

Cardiologists use coronary artery calcification, measured in CAC scores, to determine heart disease risk. Why does exercise increase it?
How Well Do CAC Scores Predict Heart Attack Risk?
Close up young indian female cardiologist holding cellphone and stethoscope.

Do you have plaque in your coronary arteries? Unless you have had symptoms that sent you to a coronary cath lab, you might not know. Over the last decade or two, though, doctors have used CT scans to calculate CAC scores. These offer a way to determine coronary artery calcification (Journal of the American College of Cardiology, July 24, 2018). These calcium-containing hard plaques are a visible indicator of coronary artery disease. Consequently, doctors have embraced the scores as an additional way of predicting a person’s risk for a heart attack. Two new studies call the value of CAC scores into question, however.

Vigorous Exercise Linked to Higher CAC Scores:

Everyone recognizes that physical activity is beneficial for the heart. People who exercise regularly are less likely to have heart attacks or die from cardiovascular causes. Vigorous exercisers seem to get particular benefit.

New research utilizing a comprehensive Korean database has turned up an interesting paradox, though (Heart, Sept. 20, 2021). Over 25,000 adults participated in the study. The investigators scanned their coronary arteries at least twice between 2011 and 2017. They also measured weight, cholesterol and blood pressure for each volunteer, who answered questions about family history and physical activity.

Those who exercised regularly—the equivalent of running 4 miles a day every day—were most likely to have high CAC scores. In addition, their scores increased more rapidly over the course of the study. The doctors don’t know what to make of the accelerated progression of coronary artery calcification in vigorous exercisers. They note, however, that physical activity is good for the cardiovascular system. While no one is about to tell people to stop exercising, it does pose a puzzle with respect to the CAC.

Statin Therapy and a CAC Paradox:

Another interesting paradox involves statin therapy to lower LDL cholesterol (JAMA Cardiology, Aug. 18, 2021). Generally, doctors prescribe cholesterol-lowering statins for patients with CAC scores at or above 100.

However, a study published in JAMA Cardiology showed that people taking statins had

“larger increases of high-density calcium…plaque compared with plaques in patients not treated with statins.”

This high-density calcium plaque grew more slowly among patients taking statins. The investigators can only speculate as to why statins lead to higher CAC scores. One of our frequent guest experts, Dr. Steve Nissen, chairman of the Robert and Suzanne Tomsich Department of Cardiovascular Medicine at the Cleveland Clinic, has described why he does not routinely get calcium scores on his heart patients.

In the future, cardiologists will need to learn why both intense exercise and statin therapy appear to accelerate calcified plaque progression. After all, both presumably protect patients from heart attacks. These findings suggest that the coronary artery calcium scan might not be the best way to predict cardiovascular complications.

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About the Author
Terry Graedon, PhD, is a medical anthropologist and co-host of The People’s Pharmacy radio show, co-author of The People’s Pharmacy syndicated newspaper columns and numerous books, and co-founder of The People’s Pharmacy website. Terry taught in the Duke University School of Nursing and was an adjunct assistant professor in the Department of Anthropology. She is a Fellow of the Society of Applied Anthropology. Terry is one of the country's leading authorities on the science behind folk remedies. .
  • Greenland P et al, "Coronary calcium score and cardiovascular risk." Journal of the American College of Cardiology, July 24, 2018. DOI: 10.1016/j.jacc.2018.05.027
  • Sung K-C et al, "Physical activity and the progression of coronary artery calcification." Heart, Sept. 20, 2021. DOI: 10.1136/heartjnl-2021-319346
  • van Rosendael AR et al, "Association of statin treatment with progression of coronary atherosclerotic plaque composition." JAMA Cardiology, Aug. 18, 2021. doi:10.1001/jamacardio.2021.3055
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