title: Variability of phase shift between blood pressure and heart rate fluctuations: a marker of short-term circulation control.
abstract: BACKGROUND
  We postulated that the variability of the phase shift between blood pressure and heart rate fluctuation near the frequency of 0.10 Hz might be useful in assessing autonomic circulatory control.
  
  
  RESULTS
  We tested this hypothesis in 4 groups of subjects: 28 young, healthy individuals; 13 elderly healthy individuals; 25 patients with coronary heart disease; and 19 patients with a planned or implanted cardioverter-defibrillator (ICD recipients). Data from 5 minutes of free breathing and at 2 different, controlled breathing frequencies (0.10 and 0.33 Hz) were used. Clear differences (P<0.001) in variability of phase were evident between the ICD recipients and all other groups. Furthermore, at a breathing frequency of 0.10 Hz, differences in baroreflex sensitivity (P<0.01) also became evident, even though these differences were not apparent at the 0.33-Hz breathing frequency.
  
  
  CONCLUSIONS
  The frequency of 0.10 Hz represents a useful and potentially important one for controlled breathing, at which differences in blood pressure-RR interactions become evident. These interactions, whether computed as a variability of phase to define stability of the blood pressure-heart rate interaction or defined as the baroreflex sensitivity to define the gain in heart rate response to blood pressure changes, are significantly different in patients at risk for sudden arrhythmic death. In young versus older healthy individuals, only baroreflex gain is different, with the variability of phase being similar in both groups. These measurements of short-term circulatory control might help in risk stratification for sudden cardiac death.
authors.affiliation: Institute of Scientific Instruments, Academy of Sciences, Královopolská 147, 612 64 Brno, Czech Republic. josef@isibrno.cz
authors.forename: Josef
authors.initials: J
authors.lastname: Halámek
authors.forename: Tomás
authors.initials: T
authors.lastname: Kára
authors.forename: Pavel
authors.initials: P
authors.lastname: Jurák
authors.forename: Miroslav
authors.initials: M
authors.lastname: Soucek
authors.forename: Darrel P
authors.initials: DP
authors.lastname: Francis
authors.forename: L Ceri
authors.initials: LC
authors.lastname: Davies
authors.forename: Win K
authors.initials: WK
authors.lastname: Shen
authors.forename: Andrew J S
authors.initials: AJ
authors.lastname: Coats
authors.forename: Miroslav
authors.initials: M
authors.lastname: Novák
authors.forename: Zuzana
authors.initials: Z
authors.lastname: Nováková
authors.forename: Roman
authors.initials: R
authors.lastname: Panovský
authors.forename: Jirí
authors.initials: J
authors.lastname: Toman
authors.forename: Josef
authors.initials: J
authors.lastname: Sumbera
authors.forename: Virend K
authors.initials: VK
authors.lastname: Somers
mesh_terms: D000328:Adult; D000367:Age Factors; D000368:Aged; D001145:Arrhythmias, Cardiac / Q000503:physiopathology / Q000628:therapy; D001341:Autonomic Nervous System / Q000502:physiology / Q000503:physiopathology; D017704:Baroreflex / Q000502:physiology; D001775:Blood Circulation / Q000502:physiology; D001794:Blood Pressure / Q000502:physiology; D003327:Coronary Disease / Q000503:physiopathology*; D017147:Defibrillators, Implantable; D005260:Female; D006339:Heart Rate / Q000502:physiology; D006801:Humans; D008297:Male; D008875:Middle Aged; D011237:Predictive Value of Tests; D012016:Reference Values; D012119:Respiration; D018570:Risk Assessment; D013997:Time Factors