An investigation of nitric oxide metabolites during symptomatic myocardial ischaemia in relation to exercise tolerance test.

BACKGROUND

Nitric oxide (NO) plays a pivotal role in the pathophysiology of coronary heart disease (CHD). Low plasma concentrations of NO metabolites (nitrite and nitrate), the stable oxidation products of NO have been reported in patients with CHD but this is controversial. Plasma nitrite and nitrate concentrations during symptomatic myocardial ischaemia and in response to exercise in subjects with CHD have not been studied. We therefore measured plasma nitrite and nitrate concentrations in subjects before and after an exercise tolerance test (ETT).

MATERIAL/METHODS: Plasma nitrite and nitrate concentrations were measured before and after an ETT in 24 subjects with symptomatic exercise-induced myocardial ischaemia (positive ETT) and in 27 subjects without exercise-induced myocardial ischaemia (negative ETT).

RESULTS

Plasma nitrate concentrations were higher (p<0.002) before and after the ETT in subjects with a positive ETT (31.51+/-21.80 mol/L and 30.86+/-21.42 mol/L respectively) than in the subjects with a negative ETT (14.75+/-6.71 mol/L and 15.64+/-6.50 mol/L respectively). Plasma nitrite concentrations before and after the ETT were similar in both groups. Within each group, plasma nitrite and nitrate concentrations were not altered by exercise.

CONCLUSIONS

Subjects with exercise-induced myocardial ischaemia have higher plasma nitrate concentration than subjects without exercise-induced myocardial ischaemia. This is consistent with either a compensatory or an inflammatory response of the vascular endothelium to endothelial damage. Symptomatic exercise-induced ischaemia is not associated with altered plasma NO metabolite concentrations.