EXPERT ANALYSIS FROM THE AHA SCIENTIFIC SESSIONS
CHICAGO (FRONTLINE MEDICAL NEWS) – Coronary artery calcium testing has established itself as a true “game changer” in primary cardiovascular prevention, proponents of the risk-stratification tool said at the American Heart Association scientific sessions.
Knowing a patient’s coronary artery calcium score facilitates a more informed physician-patient discussion and shared decision making regarding whether to go on decades-long statin therapy, according to Dr. Khurram Nasir of the center for prevention and wellness research at Baptist Health Medical Center in Miami Beach.
“In our view, a much underappreciated value of coronary artery calcium testing lies in the power of zero. Roughly half of adults have a coronary artery calcium score of 0, and this results in a very low cardiovascular event rate,” the cardiologist said.
He presented an analysis of 4,758 nondiabetic participants in the prospective, population-based MESA (Multi-Ethnic Study of Atherosclerosis) in which he examined how they fared in terms of cardiovascular events over a median 10.3 years of follow-up. All were free of known cardiovascular disease at baseline. With the risk estimator included in the 2013 AHA/ACC cholesterol management guidelines, 2,377 subjects would be recommended for high-intensity statin therapy at baseline on the basis of a 10-year atherosclerotic cardiovascular disease risk estimate of at least 7.5%. Another 589 participants were recommended for consideration of a moderate-intensity statin based on an estimated 10-year risk of 5%-7.4%.
Forty-one percent of MESA subjects recommended for a high-intensity statin according to the AHA/ACC risk estimator had a coronary artery calcium (CAC) score of 0, and their 10-year composite rate of MI, stroke, or cardiovascular death was just 4.9% – well below the 7.5% threshold recommended for statin therapy. In contrast, if any CAC was present, the event rate was 10.5%.
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.
Other situations where he finds CAC testing useful in daily practice include uncertainty as to a patient’s true risk level because the individual’s situation isn’t adequately captured by the AHA/ACC risk estimator. A patient with rheumatologic disease would be one example; another would be an individual who is neither white nor African American. He said he also utilizes CAC testing in statin-intolerant patients, where the results are useful in deciding how many different statins to try before saying “enough.”
Audience members asked what it’s going to take to get insurers to cover CAC testing for risk stratification. Dr. Blaha replied that more long-term outcomes and cost-effectiveness data are coming. In the meantime, at an out-of-pocket cost of $75-$100, a lot of his statin-reluctant patients consider CAC testing a good buy.
“They say, ‘I’ll take this test to help me decide whether to take a pill for the rest of my life,’” according to Dr. Blaha.
Dr. Nasir said the evidence in support of CAC testing is now so strong that he believes physicians have an obligation to mention it as an option during the statin treatment decision discussion.
“At this moment, most patients are making their decision based on the guesstimate of their risk we are giving them using the risk calculator. If they have the ability through a $75-$100 test that costs about the same as 18 months of statin therapy to know that their true risk is not, say, 10%, but actually 5%, they’re less likely to choose therapy. Is it even ethical to withhold from our patients that there is a test out there that can reduce their estimated risk to a point that they can avoid statin therapy?” the cardiologist asked.
Dr. Nasir reported serving on an advisory board for Quest Diagnostics. Dr. Blaha reported having no financial conflicts.
