Objectives. This study sought to examine effect of vitamin C, an antioxidant, on the abnormal vasomotor reactivity in spasm coronary arteries.
Background. Oxygen free radicals generated in the arterial walls have been shown to cause endothelial vasomotor dysfunction.
Methods. Responses of the epicardial arterial diameters of the left coronary arteries to the intracoronary infusion of acetylcholine (ACh) (10 and 50 µg/min) were measured by quantitative coronary angiography before and during combined intracoronary infusion of vitamin C (10 mg/min) or saline as a placebo in 32 patients with coronary spastic angina and in 34 control subjects.
Results. Vitamin C infusion suppressed the constrictor response of the epicardial diameter to ACh in spasm coronary arteries but had no significant effect in the control coronary arteries (percent change in distal diameter in response to 10 µg/min of ACh [constriction (–), dilation (+), mean ± SEM] before vitamin C: –8.2 ± 2.9% in spasm arteries, +8.4 ± 2.9%* in control arteries; during vitamin C: +0.2 ± 3.8%* in spasm arteries, +7.2 ± 1.3%* in control arteries [*p < 0.01 vs. spasm arteries before vitamin C]). The coronary sinus–arterial difference in plasma thiobarbituric acid reactive substances during ACh infusion, an indicator of lipid peroxidation in coronary circulation, was higher in patients with coronary spastic angina than in control subjects (p < 0.01) but was suppressed in patients with coronary spastic angina to comparable levels in control subjects by combined infusion of vitamin C. Saline infusion had no effect.