title: Endothelial function fluctuates with diurnal variation in the frequency of ischemic episodes in patients with variant angina.
abstract: OBJECTIVE
  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 AM), afternoon (2 PM) and evening (8 PM) 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 PM vs. 6 AM vs. 2 PM: 7.8 +/- 2.1% (p < 0.01 vs. VA at 6 AM) vs. 5.4 +/- 2.3% vs. 8.8 +/- 1.9% (p < 0.01 vs. VA at 6 AM); 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 PM to midnight: 7 episodes; midnight to 8 AM: 25 episodes; 8 AM to 4 PM: 3 episodes).
  
  
  CONCLUSIONS
  There is diurnal fluctuation in endothelial function, which is associated with variation in the frequency of ischemic episodes.
authors.affiliation: Department of Cardiovascular Medicine, Kumamoto University School of Medicine, 1-1-1 Hongo, Kumamoto City 860-8556, Japan. koumei@gpo.kumamoto-u.ac.jp
authors.forename: Hiroaki
authors.initials: H
authors.lastname: Kawano
authors.forename: Takeshi
authors.initials: T
authors.lastname: Motoyama
authors.forename: Hirofumi
authors.initials: H
authors.lastname: Yasue
authors.forename: Nobutaka
authors.initials: N
authors.lastname: Hirai
authors.forename: Hesham M
authors.initials: HM
authors.lastname: Waly
authors.forename: Kiyotaka
authors.initials: K
authors.lastname: Kugiyama
authors.forename: Hisao
authors.initials: H
authors.lastname: Ogawa
mesh_terms: D000368:Aged; D000788:Angina Pectoris, Variant / Q000503:physiopathology*; D002940:Circadian Rhythm; D003326:Coronary Circulation; D004730:Endothelium, Vascular / Q000503:physiopathology*; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged