Vitamin C improves endothelial function of epicardial coronary arteries in patients with hypercholesterolaemia or essential hypertension?assessed by cold pressor testing.
Aims There is evidence that formation of free radicals increases in patients with hypertension or hypercholesterolaemia, which may contribute to endothelial dysfunction of epicardial coronary arteries due to inactivation of the vasodilator NO. The present study was designed to test whether the abnormal constriction of epicardial coronary arteries due to sympathetic stimulation by the cold pressor test in patients with essential hypertension or hypercholesterolaemia could be reversed by administration of the antioxidant vitamin C.
Methods and Results In 28 patients without relevant coronary artery stenosis the cold pressor test was performed before and after a 3g infusion of vitamin C. In five normal controls the cold pressor test led to a similar increase in luminal area before and after vitamin C (3·7±1·3% and 1·9±0·8%, ns vs before vitamin C). In nine hypercholesterolaemic patients the cold pressor test led to a –14·1±2·8% reduction in cross-sectional area before vitamin C. This constriction was significantly improved after vitamin C to –7·6%±2·0, P=0·027 vs before vitamin C. In nine hypertensive patients, the cold pressor test led to a –17·1±3·2% decrease in cross-sectional area before vitamin C, which was improved to –7·1±3·1 after vitamin C, P=0·004 vs before vitamin C. This increase in luminal area was significant in each group in comparison with normal controls (each P<0·05). Administration of saline (placebo group, five patients) had no significant effect on cold pressor test-induced constriction (–6·9±3·9% before and –6·8±3·7% after saline).
Conclusion The antioxidant vitamin C reverses cold pressor test-induced vasoconstriction of epicardial coronary arteries in patients with hypertension or hypercholesterolaemia. Our data suggest that enhanced oxidative stress contributes to impaired endothelial function in this patient population.