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Metformin for Non-Diabetic Patients With Coronary Heart Disease (The CAMERA Study): A Randomized Controlled Trial
Study Questions:
What is the impact of metformin on progression of mean carotid intima-media thickness (cIMT) in nondiabetic patients with pre-existing coronary heart disease?
Methods:
The CAMERA (Carotid Atherosclerosis Metformin for insulin ResistAnce) study was a single-center, randomized, placebo-controlled, double-blind trial. Patients with pre-existing coronary heart disease (previous acute coronary syndrome, coronary artery bypass surgery, or angiographically proven coronary heart disease) and large waist circumference were randomly assigned to metformin or placebo. Mean cIMT was assessed with carotid artery ultrasonography at baseline, 12 months, and 18 months. The primary endpoint was progression of mean distal common carotid artery cIMT at 18 months.
Results:
Among 173 participants (86 in the metformin group and 87 in the placebo group), cIMT progression did not differ significantly between groups (slope difference 0.007 mm/year, 95% confidence interval -0.006 to 0.020; p = 0.29). Metformin significantly reduced all measures of adiposity, compared to placebo, at 18 months (p < 0.001 for all). All 173 participants were concomitantly taking statin medications.
Conclusions:
The authors concluded that in nondiabetic patients with pre-existing coronary heart disease already taking statin medications, metformin had no effect on cIMT.
Perspective:
Metformin has a favorable effect on cardiovascular outcomes in patients with type 2 diabetes mellitus. The authors of the CAMERA study suggest that, in contrast to its role in diabetic patients, metformin may not have a role for improving cardiovascular outcomes in nondiabetic patients with pre-existing coronary heart disease. As articulated in an accompanying editorial, it is unclear whether progression of cIMT is the best representation of cardiovascular outcome. Until large, randomized clinical trials will help more definitively establish the role of metformin in nondiabetic patients with high cardiovascular risk, metformin does not appear to have a valid place in this setting.
Keywords: Coronary Artery Disease, Acute Coronary Syndrome, Carotid Intima-Media Thickness, Hydroxymethylglutaryl-CoA Reductase Inhibitors, Diabetes Mellitus, Type 2, Coronary Disease, Carotid Artery Diseases, Insulin Resistance, Waist Circumference, Carotid Artery, Common, Metformin, Cardiovascular Diseases, Obesity, Confidence Intervals, Coronary Artery Bypass
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