Coronary artery calcium scans are becoming an increasingly popular way to assess a person’s future risk of heart disease. The quick and relatively inexpensive CT test measures calcium buildup in the arteries that supply blood to the heart.
But new research from Northwestern Medicine suggests that the scan may provide its greatest benefit to a smaller group of patients than previously assumed.
Researchers followed more than 6,000 adults for 10 years and found that, for the overall study population, adding a coronary artery calcium score provided only a small improvement over PREVENT, the American Heart Association’s main cardiovascular risk calculator.
How Cardiac Calcium Scans Measure Risk
PREVENT estimates the probability that a person will develop cardiovascular disease over the next 10 to 30 years using commonly available health information (such as blood pressure, cholesterol, age, and sex).
A coronary artery calcium scan takes a different approach. The CT scan looks for calcium-containing plaques within the coronary arteries. The resulting calcium score reflects the amount of detectable calcified plaque. In general, a higher score is associated with a higher risk of future cardiovascular disease.
The new findings suggest that calcium scores become particularly useful when PREVENT initially places someone in a borderline or intermediate risk category. Among these patients, additional screening provided a clearer indication of who was more likely to develop cardiovascular disease and who was less likely.
“Coronary artery calcium scans are becoming more available and less expensive,” said the study’s senior author, Dr. Nilay Shah, an assistant professor of medicine in the division of cardiology at Northwestern University Feinberg School of Medicine. “Our findings suggest that not everyone necessarily needs or would benefit from a coronary artery calcium scan in order to predict the risk of heart attack and stroke.”
Shah said the findings also highlight the potential disadvantages of using scans when they are unlikely to change a patient’s treatment.
“Routine use of a calcium scan in low-risk individuals may result in unnecessary radiation exposure, testing, and costs with unclear clinical benefits,” Shah added. “Using calcium scans in high-risk people is likely to result in unnecessary testing because these people are recommended to start a statin regardless of what the calcium scan shows.”
The study was published on August 26 in JAM.
Comparison of predictions with actual results
To investigate how much additional information calcium scans provide, Shah and colleagues examined data from more than 6,000 adults ages 45 to 79 who participated in the Multi-Ethnic Atherosclerosis Study.
At the beginning of the study, each participant received both a coronary artery calcium score and a PREVENT estimate of their probability of experiencing a cardiovascular event in the next 10 years.
Investigators then tracked down what really happened.
Over the next decade, 6% of participants suffered a heart attack or stroke. When the team compared predictions that included calcium scores with those based solely on PREVENT, the overall improvement was modest.
The model’s discrimination, which measures how well it distinguishes between people who will and will not experience a cardiovascular event, increased only slightly. It increased from 0.73 with PREVENT to 0.75 when calcium scores were included.
However, the picture changed when researchers focused specifically on people whose initial PREVENT scores placed them in the borderline or intermediate risk categories (those initially considered to have between a 3% and 9% 10-year risk of heart disease).
For this group, including the calcium score produced a more significant improvement in predicting future cardiovascular events.
“For patients at borderline risk, knowing their calcium score can help determine whether their risk is actually lower or higher than initially estimated, which can help guide treatment decisions,” Shah explained.
Find the patients most likely to benefit
About 10% of American adults ages 30 to 79 suffer from cardiovascular disease, which remains the leading cause of death in the country. However, many heart attacks, strokes and other cardiovascular events can be prevented, Shah said.
Accurately identifying a person’s risk can help doctors determine who is most likely to benefit from preventive treatments, including statins, which reduce cholesterol and cardiovascular risk.
“The findings help us understand how best to use available tools to estimate someone’s risk of having a heart attack or stroke. That provides a more precise guide to who is most likely to benefit from using a statin to help prevent heart disease,” Shah said.
Shah added that the results also support the clinical utility of the relatively new PREVENT calculator. Even without calcium scan results, PREVENT performed well in predicting cardiovascular risk.
Questions that still need answers
The researchers said additional studies are needed to determine how much PREVENT calcium scores improve estimates in certain populations.
That includes higher-risk groups, such as South Asian adults and Filipinos, Shah noted. More research is also needed in younger people because the participants in this study were between 45 and 79 years old when the research began.
Other Northwestern co-authors include Xiaoning Huang, Lucia Petito, Norrina Allen, Dr. Philip Greenland, and Dr. Sadiya Khan.
The study is titled “Predictive utility of coronary artery calcium added to equations to PREVENT atherosclerotic cardiovascular disease.” It was supported by the American Heart Association (grant 24CDA1266732) and the National Heart, Lung, and Blood Institute (contracts 75N92020D00001, HHSN268201500003I, N01-HC-95159, 75N92020D00005, N01-HC-95160, 75N92020D00002, N01-HC-95161, 75N92020D00003, N01-HC-95162, 75N92020D00006, N01-HC-95163, 75N92020D00004, N01-HC-95164, 75N92020D00007, N01-HC-95165, N01-HC-95166, N01-HC-95167, N01-HC-95168, N01-HC-95169 and grant K23HL157766).