Endothelial function fluctuates with diurnal variation in the frequency of ischemic episodes in patients with variant angina

Objectives The aim of the present study was to investigate whether there is diurnal fluctuation in the endothelial function of patients with variant angina (VA). Background Coronary spasm is induced by acetylcholine and is promptly relieved by nitroglycerin. Thus, it is possible that endothelial dysfunction is involved in the pathogenesis of coronary spasm. Furthermore, the frequency of ischemic episodes is known to display diurnal variation. Methods Flow-mediated, endothelium-dependent vasodilation of the brachial arteries was measured in the early morning (6 image), afternoon (2 image) and evening (8 image) in 20 patients with VA (mean age 54.5 years; 10 men and 10 women) and in 20 control subjects (mean age 54.2 years; 10 men and 10 women). All patients underwent 24-h ambulatory electrocardiographic monitoring during the study. Results Flow-mediated vasodilation in patients with VA was deteriorated by the early morning and improved by the afternoon (patients with VA at 8 image vs. 6 image vs. 2 image: 7.8 ± 2.1% (p < 0.01 vs. VA at 6 image) vs. 5.4 ± 2.3% vs. 8.8 ± 1.9% (p < 0.01 vs. VA at 6 image); control subjects: 9.5 ± 2.8% vs. 9.0 ± 2.2% vs. 9.9 ± 1.9%, respectively). The frequency of spontaneous ischemic episodes was highest from midnight to morning and was lowest from morning to late afternoon (4 image to midnight: 7 episodes; midnight to 8 image: 25 episodes; 8 image to 4 image: 3 episodes). Conclusions There is diurnal fluctuation in endothelial function, which is associated with variation in the frequency of ischemic episodes.