How physicians are using ‘the power of zero’ in primary prevention

With a relative risk reduction with statin therapy of 30%, the number needed to treat for 5 years to prevent one cardiovascular event in the group with a CAC of 0 would be 128. In the presence of any CAC, the number needed to treat fell to a far more reasonable 56, Dr. Nasir said.

Similarly, among the group recommended for consideration of statin therapy on the basis of a 10-year risk of 5%-7.4%, the actual event rate in the 57% of subjects with a CAC of 0 was just 1.5%. If any CAC was present, the event rate shot up to 7.2%. The number needed to treat in this cohort was 445 among those with a CAC of 0 and 90 with any CAC present.

“I think coronary artery calcium is a game changer in primary prevention,” Dr. Michael J. Blaha commented. “It sufficiently moves the needle to make you think differently about a patient. I’m not sure some of the other tests have sufficient evidence to say, ‘I’m going to think about not treating you if it’s negative and treating you if it’s positive,’ but coronary artery calcium has that evidence.”

In his own cardiology practice at Johns Hopkins University, Baltimore, Dr. Blaha finds himself using CAC testing often, especially in his many statin-reluctant patients.

“I have a lot of patients who would fit under a recommendation for statin therapy under the 2013 AHA/ACC cholesterol management guidelines, but who really don’t want to take medications. I know you see these patients in your practices, too. This is lifelong therapy, and they want a really good reason to take it or not to take it. If a patient is reluctant to take a statin and has a CAC score of 0, I will sometimes emphasize lifestyle therapy. It certainly redoubles my interest in lifestyle therapy. But if the CAC score is elevated, then I can make a specific case that the number needed to treat is very favorable, compared to the number needed to harm,” explained Dr. Blaha, a coinvestigator with Dr. Nasir in the MESA study.