Coronary calcium serves as ‘iceberg in the water’ when evaluating ASCVD risk
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Although various studies have established the prognostic value of coronary artery calcium scoring for predicting atherosclerotic risk, some current models do not take coronary calcium into account, a speaker reported.
“One of the problems that we have, even with the new pooled risk equation, is that it overestimates risk,” Matthew Budoff, MD, director of cardiovascular CT at The Lundquist Institute and professor of medicine at the David Geffen School of Medicine at UCLA, said during a presentation at the Cardiometabolic Health Congress. “You would have to say that it performs quite poorly.”
To this point, Budoff cited the findings from the REGARDS trial that applied the American College of Cardiology/American Heart Association Pooled Cohort Equation to a real-world cohort of more than 300,000 individuals without known atherosclerotic CVD or diabetes.
According to the presentation, the pooled equation overestimated ASCVD risk by up to 400%.
“The problem with systematic overestimation is that that leads to overtreatment. The problem with instituting statin therapy before it's needed is that patients will then stop taking statins later in life ... when they actually need it more. Instituting it at the right time becomes critical for the patient,” Budoff said during the presentation. “You can't make an asymptomatic person feel better, but we can certainly make them feel worse with therapies like statins. We want to get the right patient on the right therapy.”
To reduce this overestimation, guidelines are starting to embrace coronary calcium as a prognostic tool for evaluating ASCVD risk, Budoff continued.
“It's not only helpful to say, 'you have some coronary calcium. I need to put you on a statin.' It's going to be more helpful to say 'you don't have any plaque. I can avoid therapy for another 5 years,'” Budoff said. “Some people are concerned about using coronary calcium scoring because it only shows the calcified plaque and not the noncalcified plaque, but that's actually not entirely true.”
According to the presentation, coronary calcium represents approximately 20% of atherosclerotic plaque in the coronary tree, similar to “an iceberg in the water,” Budoff added. Therefore, if an individual has coronary plaque, they have even more fibrotic and lipid-rich plaque. If there is no coronary calcium, there is no “iceberg in the water” and little to no ASCVD risk, he said.
A study published in The New England Journal of Medicine evaluated coronary calcium as a predictor of coronary events in the MESA cohort. Researchers observed that the risk for a coronary event was more than sevenfold among those with calcium scores between 101 and 300 and was nearly 10-fold among those with scores above 300 compared with participants with no coronary calcium (P for both < .001).
“I'm not a big believer personally in lifetime risk because we have more opportunities than one to assess a patient,” Budoff said during the presentation. “If you can reassess a patient every 5 or 10 years, you only need to predict the next 5 or 10 years to get to that next assessment point.”
In 2018, Budoff and colleagues published the 10-year outcomes data from MESA participants in the European Heart Journal. They observed that participants with a calcium score of 0 at baseline had a 10-year event rate of less than 5%, while those with score of at least 100 had an event rate of 7.5% or more.
According to the presentation, 25% of participants with a calcium score of 300 or more experienced a hard CV event such as MI, stroke or death during the 10-year follow-up.
“Coronary calcium has now been validated, not only to predict MI, but also to predict stroke,” Budoff said. “One of the reasons why the guidelines removed carotid intima-media thickness is because coronary calcium outperformed carotid IMT significantly, and they made it a class III recommendation. Not harmful, but not useful. Part of the reason is because coronary calcium not only predicted MI or death, coronary calcium with a score above 100 robustly predicted stroke.”
According to research published in 2017 in JACC: Cardiovascular Imaging, coronary calcium scoring improved risk stratification of patients at high or low risk for coronary events, in addition to current guidelines.
“Superior doctors prevent the disease. Mediocre doctors treat the disease before it becomes evident; that is, subclinical atherosclerosis. And inferior doctors treat the full-blown disease,” Budoff said, citing a quote by Huang Dee Nai-Chan, a Chinese physician who wrote the first Chinese medical text in 2600 B.C., during the presentation. “We can at least become mediocre doctors in the eyes of the ancient Chinese by identifying patients with subclinical atherosclerosis and getting them on better therapies.”
References:
- Budoff MJ, et al. Eur Heart J. 2018;doi:10.1093/eurheartj/ehy217.
- Detrano R, et al. N Engl J Med. 2008;doi:10.1056/NEJMoa072100.
- Mahabadi AA, et al. JACC Cardiovasc Imaging. 2017;doi:10.1016/j.jcmg.2016.03.022.
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Budoff M. Session II: Dyslipidemia/Atherosclerosis/Thrombosis. Presented at: Cardiometabolic Health Congress; Oct. 14-17, 2021; National Harbor, Md. (hybrid meeting).
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