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 coronary artery calcium or 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. New studies call the value of CAC scores into question, however.
How Good Are CAC Scores for Predicting the “Big One”?
Do you remember the TV show, Sanford and Son? Fred Sanford often clutched his heart claiming that he was having a heart attack, aka “The Big One!” Doctors want to protect patients from The Big One. To do that, they rely on blood tests for things like total cholesterol (TC), LDL cholesterol, triglycerides, Lp(a), HDL cholesterol and C-reactive protein (hs-CRP), a marker for inflammation.
In recent years, though, many cardiologists have added CAC scores to their list heart evaluation tools. There was a growing sense that a high score could predict the risk for a future heart attack.
Here is how the Mayo Clinic describes a heart scan:
“Measuring calcified plaque with a heart scan may allow your doctor to identify possible coronary artery disease before you have signs and symptoms.
“Your doctor will use your test results to determine what you need — medication or lifestyle changes — to reduce your risk of a heart attack or other heart problems.”
That sounds impressive. But how good are CAC scores for predicting future heart attack probability?
A Systematic Review of CAC Scores Is Unimpressive:
A meta-analysis published in JAMA Internal Medicine (April 25, 2022) analyzed data from six studies. There were 17,961 participants and 1,043 cardiovascular disease “events.”
The authors conclude that:
“Although CACS appears to add some further discrimination to standard CVD [cardiovascular disease] risk calculators, no evidence suggests that this provides clinical benefit.”
That is stuffy doctor talk. What they are trying to say is that CAC scores are not very helpful in predicting or preventing heart attacks. They go on to add that any modest gain from a heart scan may “often be outweighed by costs, rates of incidental findings, and radiation risks.”
How Much Does It Cost to Get CAC Scores?
Prices for any medical procedure can vary tremendously from one hospital to another and from one part of the country to another.
Imaging Technology News (Sept. 25, 2020) states:
“Although CAC screening provides vital health information, it is generally not covered by insurance and can cost from $400 to $800.”
As for the “vital health information,” that is now up for grabs.
An accompanying editorial (JAMA Internal Medicine, April 25, 2022) adds this:
“Until ongoing outcomes studies indicate a clinical benefit of CACS screening to counter balance its potential harms, we agree with the US Preventive Services Task Force and believe that adherence to the ancient medical dictum, primum non nocere, [first do no harm] should dictate a pause in adding CACS screening to standard clinical risk models for primary prevention of CVD.”
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.
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. Could statins actually increase CAC scores?
A reader shares a CAC Paradox:
Q. I am perplexed, as are my doctors. Because I take a statin, I have low total cholesterol and LDL levels. My Lp(a) level is also good, yet my arterial calcium score keeps climbing. What’s going on?
A. The statin you have been taking might be responsible for your increasing coronary artery calcification (CAC) score (Journal of the American College of Cardiology, April 7, 2015). (This is sometimes referred to as an Agatston score.)
The CAC has traditionally been used as a risk factor for predicting heart disease. But since statins can increase the CAC, cardiologists have been looking for other explanations (Clinical Cardiology, June 2022). Some have suggested that calcified plaque is more stable and therefore less likely to lead to a heart attack.
You can learn more about the pros and cons of statins and non-drug approaches to reducing the risk of heart disease in our eGuide to Cholesterol Control and Heart Health. This online resource may be found under the Health eGuides tab.
Another study that must confuse cardiologists was published in JAMA Cardiology. It showed that people taking statins had
“larger increases of high-density calcium…plaque compared with plaques in patients not treated with statins.”
Analysis showed that when the plaque became more dense, containing more calcium, it didn’t expand in size as much. 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.
Why Are Cardiologists Measuring Coronary Artery Calcium but Not Lp(a)?
We think it would be far more productive if cardiologists measured the blood lipid called lipoprotein (a). It is abbreviated Lp(a) is highly related to clogged coronary arteries and calcified heart valves. You can read more about this risk factor for cardiovascular disease at this link.
Why Haven’t You Been Tested for Lp(a) Levels?
Learn more about Lp(a) and many ways to reduce cardiovascular risks in our eGuide to Cholesterol Control and Heart Health. It is available under the Health eGuides tab at this website.
