Low Plasm Ascorbic Acid Independently Predicts the Presence of an Unstable Coronary Syndrome

Objectives. This study sought to investigate the relations between plasm 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. Plasm samples were obtained from 149 patients undergoing cardiac catheterization (65 with stable angina, 84 with unstable angin or myocardial infarction within 2 weeks). Twelve plasm 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 hypercholesterolemi (p = 0.02) were independent predictors of the extent of atherosclerosis. No antioxidant/oxidant marker correlated with the extent of atherosclerosis. However, lower plasm 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 plasm 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 dat 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 reduction in the overall extent of fixed disease.