How a simple test can predict your risk of heart attacks

When doctors calculate a risk score for atherosclerotic cardiovascular disease, they incorporate several factors, including age, cholesterol, smoking, and diabetes. These risk scores can help determine if a patient requires medication to control any symptoms and reduce their risk of a heart attack, but they may not be as helpful for all patients, especially if their score lands in an in-between range.

"A risk score is derived from a large population, with mathematical modeling," said Michael Blaha, codirector of the preventive cardiology program at Johns Hopkins University. "We can say that this score describes the risk of heart disease among thousands of people. But there are lots of limitations in applying them to one individual."

For certain patients, a coronary artery calcium (CAC) test can provide a more accurate estimate of their risk of atherosclerotic heart disease. A CAC test is a special type of CT scan that measures the amount of calcium in the walls of the arteries. Calcium makes up a small part of plaque buildup in the heart, and it is easy to see on a scan compared to cholesterol.

Although guidelines vary, cardiologists typically recommend statins to patients who have calcium scores over zero and will suggest higher intensity statins if scores exceed 100. Patients who have a calcium score of over 300 may need even more aggressive treatment since their risk is similar to people who have already had heart attacks.

In a 2024 study from Intermountain Health, researchers found that CAC scores were accurate predictors of risk for future heart attack, as well as mortality. In addition, patients who had a zero CAC score had three times lower risk of heart attack, as well as all-cause death. 

"The coronary artery calcium score appears to be an excellent and accurate indicator of health and overall prognosis, even beyond heart disease," said Jeffrey Anderson, a distinguished research physician at Intermountain Health and the study's principal investigator.

The CAC test "leads to more statin prescriptions, better adherence to statins, less progression of atherosclerosis and less plaque growth," said Philip Greenland, a preventive cardiologist at Northwestern University. "It tips the scale."

Why aren't more people using CAC tests?

Although the number of CAC scans used quadrupled between 2006 and 2017 and online searches for related terms have increased significantly in recent years, Blaha said that "it's still being underused compared to its value."

One reason that patients may not be getting the test is that it is rarely covered by insurance, including Medicare. Although CAC tests are relatively inexpensive compared to other tests, patients must cover the cost, which is around $100 to $300 out of pocket.

"The actual risk is much, much lower than the perceived risk," said Alexander Zheutlin, a cardiology fellow and researcher at Northwestern University. Cardiologists can also reduce doses or switch patients to different medications to reduce or avoid any painful side effects.

In general, many cardiologists see CAC tests as a persuasive tool to help patients get treatment to reduce their risk of heart attacks. According to Zheutlin, if calcium scores are more influential than traditional risk assessments alone, more patients might agree to take statins.

Stephen Patrick, a 70-year-old retired tech executive from San Francisco, was one of the people who changed their mind about taking statins after undergoing a CAC test.

"For years, I was borderline on cholesterol, and I managed to beat it back with less cheese toast" and lots of exercise, Patrick said. "I was on no meds, and I took pride in that." However, after both his total and LDL cholesterol were higher than recommended, his doctor recommended a CAC test, which returned a score of 176.

Now, Patrick takes atorvastatin, or Lipitor, daily, and his cholesterol levels have decreased significantly. "I might have tried [a statin] anyway," he said. "But the calcium score meant I had to pay more attention."