title: Circadian variation of left ventricular diastolic function in healthy people.
abstract: OBJECTIVE
  To assess whether left ventricular function shows circadian variation in healthy people.
  
  
  METHODS
  10 healthy men (7) and women (3) aged 35-50 underwent M mode echocardiography of the left ventricle and Doppler velocimetry of transmitral flow at 4 h intervals over 24 h. The participants were in hospital over the study period and their diet, meal times, and sleeping hours were standardised as far as possible.
  
  
  METHODS
  Heart rate, blood pressure, left ventricular and atrial diameters, fractional shortening, peak early and late transmitral velocities, time from the second heart sound to the early diastolic velocity peak (relaxation time), isovolumic relaxation period, acceleration and deceleration of the early transmitral flow, atrial filling fraction.
  
  
  RESULTS
  A circadian rhythm was observed in heart rate and blood pressure, but neither the left ventricular diameters and systolic function nor the left atrial size showed statistically significant diurnal trends. The relaxation time (mean (SD)) measured 144 (16) ms at 2 pm, 144 (21) ms at 6 pm, 149 (22) ms at 10 pm, 168 (23) ms at 2 am, 174 (28) ms at 6 am, and 151 (21) ms at 10 am (P = 0.009). Diurnal rhythms were seen also in the isovolumic relaxation period (P = 0.003) and in the acceleration of the early diastolic transmitral flow (P = 0.037); the lowest and highest values of flow acceleration were observed during the nocturnal and daytime hours, respectively.
  
  
  CONCLUSIONS
  The Doppler indices of left ventricular filling in healthy people show diurnal changes suggestive of a circadian rhythm in the rate of left ventricular relaxation. The most likely underlying mechanism is the day-night cycle in sympathoadrenal activity.
authors.affiliation: Department of Medicine, Päijät-Häme Central Hospital, Lahti, Finland.
authors.forename: S
authors.initials: S
authors.lastname: Voutilainen
authors.forename: M
authors.initials: M
authors.lastname: Kupari
authors.forename: M
authors.initials: M
authors.lastname: Hippelainen
authors.forename: K
authors.initials: K
authors.lastname: Karppinen
authors.forename: M
authors.initials: M
authors.lastname: Ventila
mesh_terms: D000328:Adult; D001794:Blood Pressure / Q000502:physiology; D002940:Circadian Rhythm; D003326:Coronary Circulation / Q000502:physiology; D003971:Diastole; D004452:Echocardiography; D005260:Female; D006339:Heart Rate / Q000502:physiology; D006801:Humans; D008297:Male; D008875:Middle Aged; D016277:Ventricular Function, Left / Q000502:physiology*