CAC scores aid in shared decision making

SANTA ANA PUEBLO, N.M. — Coronary artery calcium scoring is a useful tool for shared decision making for the use of statin therapy, according to a presentation at the American Society for Preventive Cardiology Congress on CVD.

Coronary artery calcium imaging is a rapid CT scan of the heart that does not require contrast and has an average cost of $100, Khurram Nasir, MD, MPH, MSc, associate professor in the section of cardiovascular medicine and director of population health and health systems research at Yale University, said in the presentation. Various studies have determined the benefits of this test in primary preventing, including MESA and the Heinz Nixdorf Recall Study.

When using the Framingham Risk Score in patients from MESA in combination with CAC imaging, patients with higher burden had an increased risk for a CV event.

Based on this and other data, the 2010 American College of Cardiology Foundation/American Heart Association guidelines to assess CV risk in asymptomatic adults gave a IIA recommendation for the use of CAC imaging in patients with intermediate risk to determine atherosclerosis burden. This information would then be used to determine whether a patient should be on lipid-lowering medication.

The guideline in 2013 updated the recommendation for CAC imaging to IIB and stated that it should only be used if a calcium score is high, according to the presentation.

“The gap between what we know and what we aim for persists, and this gap complicates everything we do,” Nasir said.

Even with this uncertainty, more people were being treated with statin therapy with the guidelines.

“I was a skeptic, but the more I read, I actually became a fan of the guidelines,” Nasir said. “The reason why is because it was a paradigm shift. It shifted all of us from chasing a decades’ old dogma of just chasing cholesterol numbers. It was in the guidelines that it’s not only about your cholesterol numbers, it’s about your risk. The higher the risk needs to be aggressive and if you have lower risk, you can have flexible roles.”

There is also a risk for miscalculation, according to the presentation. With this, there are tradeoffs with the guidelines in management and primary prevention settings, including overestimation and lowering the threshold for patients who could be candidates for statin therapy.

A study published in 2015 asked patients about their opinions on statin therapy, and two-thirds of them said that they were opposed to taking a long-term medication unless they were at high risk and it provided substantial benefit. About a quarter of these patients also would pay $1,400 out of pocket to get information that they could avoid this, according to the presentation.

“In 2015 and maybe now, our stakeholders are going to place a higher value for information … to de-risk rather than screening to allow informed individual choices but also reduce overtreatment of the population,” Nasir said.

CAC testing may also be used to identify patients who may not benefit from preventive therapy, according to the presentation.

As the risk factor profile worsens, the likelihood that a patient’s CAC score will be zero decreases and burden increases, according to the presentation. Among patients with high triglycerides, low HDL and elevated LDL, 50% will have a CAC score of zero, according to a study published in Circulation in 2014.

“The mere presence of calcium actually puts you at a much higher risk, even if you are at the lowest risk,” Nasir said.

In a study published in The Lancet in 2011, about half of patients who met the criteria for the JUPITER trial, which included a C-reactive protein concentration of greater than 2 mg/dL, would not have a CAC score, and after a 6-year follow-up, four non-cardiac events occurred.

“You can still continue to reduce events maybe in these individuals if you treat all of them, but you may have to treat close to 550 individuals for the next 5 years to potentially avoid one event,” Nasir said.

In a review published in Progress in Cardiovascular Diseases in 2015, researchers determined that risk factors do not equate the presence and burden of atherosclerosis, and one-third of patients who are typically considered to have high risk have a CAC score of zero and a reasonably low risk for atherosclerotic CVD.

New guidelines suggest that screening is not recommended, but rather CAC score should be used for shared decision making, according to the presentation.

“We want to use it in uncertain conditions,” Nasir said. “This is the paradigm shift that’s happening and I hope the next prevention guidelines can follow some of the lead out here.” – by Darlene Dobkowski

Reference:

Nasir K. What we know and don’t know about coronary artery calcium imaging. Presented at: American Society for Preventive Cardiology Congress on CVD; July 27-29, 2018; Santa Ana Pueblo, New Mexico.

Disclosure: Cardiology Today was unable to obtain relevant financial disclosures.