title: Circadian variation in coronary flow velocity reserve and its relation to α1-sympathetic activity in humans.
abstract: BACKGROUND
  The circadian change in coronary microvascular function has not been directly assessed in human beings. Recent advances in transthoracic Doppler echocardiography (TTDE) provide noninvasive, physiological assessment of coronary flow velocity reserve (CFVR).
  
  
  METHODS
  This study consisted of 20 young healthy subjects (24 ± 2 years, 20 men) who underwent CFVR examinations at 3 different times; early morning (6AM), late morning (11AM) and late evening (10PM). The flow velocity in the distal portion of the left anterior descending coronary artery was measured with TTDE at baseline and during adenosine infusion to calculate CFVR. These examinations were repeated with the intake of α1-blocker (prazosin 1mg) on the other day.
  
  
  RESULTS
  CFVR showed a circadian variation with an increase from the early morning to the late morning, following a decrease to the late evening thereafter (4.4 ± 0.9 at 6AM; 5.2 ± 1.3 at 11AM; 4.2 ± 1.1 at 10PM, p<0.001). In the study with α1-blocker, CFVR was comparable between the early morning and the late morning, whereas CFVR in the late evening was lower than those in other 2 time points (5.0 ± 1.1 at 6AM; 4.9 ± 0.9 at 11AM; 4.3 ± 0.9 at 10PM, p<0.001).
  
  
  CONCLUSIONS
  This study demonstrates that CFVR has a circadian variation in humans, with an increase from the late evening to the late morning. Adding α1-blocker ameliorated CFVR only in the early morning, indicating that α1-sympathetic activity plays a heterogeneous and important role in the circadian change of CFVR in humans.
authors.affiliation: Department of Medicine, Osaka Ekisaikai Hospital, Osaka, Japan. h-syouta@mve.biglobe.ne.jp
authors.forename: Shota
authors.initials: S
authors.lastname: Fukuda
authors.forename: Kenei
authors.initials: K
authors.lastname: Shimada
authors.forename: Kumiko
authors.initials: K
authors.lastname: Maeda
authors.forename: Toshihiro
authors.initials: T
authors.lastname: Kawasaki
authors.forename: Yasushi
authors.initials: Y
authors.lastname: Kono
authors.forename: Reiko
authors.initials: R
authors.lastname: Miyahana
authors.forename: Satoshi
authors.initials: S
authors.lastname: Jissho
authors.forename: Haruyuki
authors.initials: H
authors.lastname: Taguchi
authors.forename: Minoru
authors.initials: M
authors.lastname: Yoshiyama
authors.forename: Masatoshi
authors.initials: M
authors.lastname: Fujita
authors.forename: Junichi
authors.initials: J
authors.lastname: Yoshikawa
mesh_terms: D058668:Adrenergic alpha-1 Receptor Antagonists / Q000494:pharmacology; D000328:Adult; D001783:Blood Flow Velocity / Q000187:drug effects / Q000502:physiology*; D001794:Blood Pressure / Q000187:drug effects / Q000502:physiology; D002940:Circadian Rhythm / Q000187:drug effects / Q000502:physiology*; D003326:Coronary Circulation / Q000187:drug effects / Q000502:physiology*; D003331:Coronary Vessels / Q000187:drug effects / Q000502:physiology; D006339:Heart Rate / Q000187:drug effects / Q000502:physiology; D006801:Humans; D008297:Male; D018340:Receptors, Adrenergic, alpha-1 / Q000502:physiology*; D055815:Young Adult
chemical_list: D058668:Adrenergic alpha-1 Receptor Antagonists; D018340:Receptors, Adrenergic, alpha-1