Low Plasma Ascorbic Acid Independently Predicts the Presence of an Unstable Coronary Syndrome 11Dr. Vita is supported by Grants HL-53398 and HL-559993, and Dr. Frei by Grants HL-49954 and HL-56170, from the National Heart, Lung, and Blood Institute, National Institutes of Health, Bethesda, Maryland. Dr. Frei is also supported by Grant ES-06593 from the National Institute of Environmental Health Sciences, National Institutes of Health. Dr. Keaney is the recipient of a Clinical Investigator Development Award from the National Institutes of Health, and Dr. Vita is the recipient of an Established Investigator Award from the American Heart Association, Dallas, Texas.

AbstractObjectives. This study sought to investigate the relations between plasma antioxidant status, extent of atherosclerosis and activity of coronary artery disease.Background. Previous studies indicate that increased antioxidant intake is associated with decreased coronary disease risk, but the underlying mechanisms remain controversial.Methods. Plasma samples were obtained from 149 patients undergoing cardiac catheterization (65 with stable angina, 84 with unstable angina or a myocardial infarction within 2 weeks). Twelve plasma antioxidant/oxidant markers were measured and correlated with the extent of atherosclerosis and the presence of an unstable coronary syndrome.Results. By multiple linear regression analysis, age (p < 0.001), diabetes mellitus (p < 0.001), male gender (p < 0.001) and hypercholesterolemia (p = 0.02) were independent predictors of the extent of atherosclerosis. No antioxidant/oxidant marker correlated with the extent of atherosclerosis. However, lower plasma ascorbic acid concentration predicted the presence of an unstable coronary syndrome by multiple logistic regression (odds ratio [OR] 0.59, 95% confidence interval [CI] 0.40 to 0.89, p = 0.01). The severity of atherosclerosis also predicted the presence of an unstable coronary syndrome (OR 1.7, 95% CI 1.14 to 2.47, p = 0.008) when all patients were considered. When only patients with significant coronary disease were considered (at least one stenosis >50%), ascorbic acid concentration (OR 0.56, 95% CI 0.37 to 0.85, p = 0.008) and total plasma thiols (OR 0.52, 95% CI 0.34 to 0.80, p = 0.004) predicted the presence of an unstable coronary syndrome, whereas the extent of atherosclerosis did not.Conclusions. These data are consistent with the hypothesis that the beneficial effects of antioxidants in coronary artery disease may result, in part, by an influence on lesion activity rather than a reduction in the overall extent of fixed disease