Measure of coronary artery calcium might spare statins in some elderly patients

Withholding statins in elderly patients with no coronary artery calcium (CAC) or carotid plaque burden could spare many of them from taking a pill that would benefit only a few, according to a study of an individualized, disease-guided approach.

The 2013 American College of Cardiology (ACC)/American Heart Association (AHA) guideline recommends statins for primary prevention for individuals with at least a 7.5% 10-year risk for atherosclerotic cardiovascular disease (ASCVD). Everyone living long enough will become eligible for risk-based statin therapy due to age alone, the authors of this study noted, so they sought to personalize risk-based statin eligibility using noninvasive assessment of subclinical atherosclerosis.

Researchers used data from BioImage, a prospective observational cohort of men 55 to 80 years of age and women 60 to 80 years of age without known ASCVD at baseline from January 2008 to June 2009. In 5,805 participants, those with at least a 7.5% 10-year ASCVD risk were down-classified from statin eligible to ineligible if imaging revealed no CAC or carotid plaque burden. Intermediate-risk individuals were up-classified from optional to clear statin eligibility if CAC score was at least 100 (or if they had equivalent carotid plaque burden).

The study results were published online Aug. 22 by the Journal of the American College of Cardiology.

At a median follow-up of 2.7 years, 91 patients had coronary heart disease and 138 had experienced a cardiovascular disease event. If statins were dosed statins based just on ACC/AHA guidelines, 86% of patients qualified for statin therapy, which resulted in high sensitivity (96%) but low specificity (15%) for these negative outcomes. Thirty-two percent of patients had CAC scores of 0, and 23% had carotid plaque burden scores of 0. CAC-guided reclassification improved specificity for coronary heart disease events by 22% (P<0.0001) without any significant loss in sensitivity, yielding a binary net reclassification index (NRI) of 0.20 (P<0.0001). Reclassification based on carotid plaque burden improved specificity 16% (P<0.0001) with a minor loss in sensitivity (7%), yielding an NRI of 0.09 (P=0.001). For cardiovascular disease events, the NRI was 0.14 (CAC-guided) and 0.06 (carotid plaque burden-guided). The positive NRIs were driven primarily by down-classifying the large subpopulation with a CAC or carotid plaque burden score of 0.

The individualized approach is simple and easy to implement in routine clinical practice, the authors wrote. The reclassification approach based on well-defined cut-points for CAC (and corresponding carotid plaque burden cut-points) led to less overtreatment than treating based just on the guidelines, with no or only minor loss in sensitivity. “Limiting primary prevention with statins to individuals with CAC>0 could spare 1 in 4 elderly patients from taking medication that will benefit only a few,” the authors wrote.

An editorial noted that follow-up in the study was a mean of only 2.7 years, while the pooled cohort equivalents of the guidelines estimate 10-year risk. Most patients, 97.5%, would not have been expected to have any events during the study. Still, the editorial concluded, “given that imaging might identify up to one-third of the statin-eligible population who could do well without chronic lipid-lowering therapy, physicians may consider incorporating such a strategy in their discussion with patients about reducing CVD risk.”