title: Relationship between R-R interval variation and left ventricular function in sinus rhythm and atrial fibrillation as estimated by means of heart rate variability fraction.
abstract: BACKGROUND
  Reduced heart rate variability (HRV) is associated with a poor outcome in patients with sinus rhythm (SR) or atrial fibrillation (AF). However, cut-off points for HRV measures differ between SR and AF. We hypothesized that a global index of 24-hour HRV based on evaluation of scatterplot would describe HRV irrespective of cardiac rhythm.
  
  
  METHODS
  407 patients with ischemic heart disease (317 male, 90 female, mean age 57 ± 9 years) were studied. 331 patients had SR and 76 patients had AF. 24-hour ECGs were recorded, and standard HRV indices were calculated. Scatterplots was used to determine the HRV fraction (HRVF, %). HRV measures were compared in respect to left ventricular ejection fraction (LVEF £ 35% or 〉 35%).
  
  
  RESULTS
  Standard HRV measures were higher in AF-patients despite the mean RR interval was lower. In patients with LVEF £ 35%, standard HRV indices were lower in SR group, in AF group only SDNN and RMSSD were reduced. The HRVF was comparably reduced (SR 39.3 ± 15.3%, AF 37.3 ± 17.9%). In patients with LVEF 〉 35%, HRVF did not differ between SR (47.2 ± ± 10.5%) and AF (46.1 ± 12.1%). The HRVF correlated with SDNN and SDANN (~0.85) in SR. Correlations were weaker in AF (~0.6). Standard HRV indices and HRVF showed similar relations with LVEF, but only in AF at the same range.
  
  
  CONCLUSIONS
  The HRV fraction allows for HRV evaluation irrespective of cardiac rhythm. The index elicited a similar dependence of HRV on left ventricular function in SR and AF.
authors.affiliation: 3rd Chair of Cardiology, Medical University of Silesia, Katowice, Poland. maciej.sosnowski@gmail.com
authors.forename: Maciej
authors.initials: M
authors.lastname: Sosnowski
authors.forename: Barbara
authors.initials: B
authors.lastname: Korzeniowska
authors.forename: Peter W
authors.initials: PW
authors.lastname: Macfarlane
authors.forename: Michał
authors.initials: M
authors.lastname: Tendera
mesh_terms: D000368:Aged; D001281:Atrial Fibrillation / Q000175:diagnosis / Q000503:physiopathology*; D016009:Chi-Square Distribution; D015716:Electrocardiography, Ambulatory; D005260:Female; D006339:Heart Rate; D006801:Humans; D008297:Male; D008875:Middle Aged; D009203:Myocardial Infarction / Q000175:diagnosis / Q000503:physiopathology*; D017202:Myocardial Ischemia / Q000175:diagnosis / Q000503:physiopathology*; D011044:Poland; D011237:Predictive Value of Tests; D011379:Prognosis; D012815:Signal Processing, Computer-Assisted; D013318:Stroke Volume; D013997:Time Factors; D016277:Ventricular Function, Left