title: Fractal correlation properties of R-R interval dynamics and mortality in patients with depressed left ventricular function after an acute myocardial infarction.
abstract: BACKGROUND
  Preliminary data suggest that the analysis of R-R interval variability by fractal analysis methods may provide clinically useful information on patients with heart failure. The purpose of this study was to compare the prognostic power of new fractal and traditional measures of R-R interval variability as predictors of death after acute myocardial infarction.
  
  
  RESULTS
  Time and frequency domain heart rate (HR) variability measures, along with short- and long-term correlation (fractal) properties of R-R intervals (exponents alpha(1) and alpha(2)) and power-law scaling of the power spectra (exponent beta), were assessed from 24-hour Holter recordings in 446 survivors of acute myocardial infarction with a depressed left ventricular function (ejection fraction </=35%). During a mean+/-SD follow-up period of 685+/-360 days, 114 patients died (25.6%), with 75 deaths classified as arrhythmic (17.0%) and 28 as nonarrhythmic (6.3%) cardiac deaths. Several traditional and fractal measures of R-R interval variability were significant univariate predictors of all-cause mortality. Reduced short-term scaling exponent alpha(1) was the most powerful R-R interval variability measure as a predictor of all-cause mortality (alpha(1) <0.75, relative risk 3.0, 95% confidence interval 2.5 to 4.2, P<0.001). It remained an independent predictor of death (P<0.001) after adjustment for other postinfarction risk markers, such as age, ejection fraction, NYHA class, and medication. Reduced alpha(1) predicted both arrhythmic death (P<0.001) and nonarrhythmic cardiac death (P<0.001).
  
  
  CONCLUSIONS
  Analysis of the fractal characteristics of short-term R-R interval dynamics yields more powerful prognostic information than the traditional measures of HR variability among patients with depressed left ventricular function after an acute myocardial infarction.
authors.affiliation: Division of Cardiology, Department of Medicine, University of Oulu, Finland. heikki.huikuri@oulu.fi
authors.forename: H V
authors.initials: HV
authors.lastname: Huikuri
authors.forename: T H
authors.initials: TH
authors.lastname: Mäkikallio
authors.forename: C K
authors.initials: CK
authors.lastname: Peng
authors.forename: A L
authors.initials: AL
authors.lastname: Goldberger
authors.forename: U
authors.initials: U
authors.lastname: Hintze
authors.forename: M
authors.initials: M
authors.lastname: Møller
mesh_terms: D000319:Adrenergic beta-Antagonists / Q000627:therapeutic use; D000368:Aged; D000806:Angiotensin-Converting Enzyme Inhibitors / Q000627:therapeutic use; D002423:Cause of Death; D003718:Denmark; D015716:Electrocardiography, Ambulatory; D005260:Female; D017709:Fractals; D006339:Heart Rate; D006801:Humans; D008297:Male; D008875:Middle Aged; D009203:Myocardial Infarction / Q000188:drug therapy / Q000401:mortality* / Q000503:physiopathology*; D016019:Survival Analysis; D015912:Thrombolytic Therapy; D013997:Time Factors; D018487:Ventricular Dysfunction, Left / Q000401:mortality / Q000503:physiopathology*; D016277:Ventricular Function, Left
chemical_list: D000319:Adrenergic beta-Antagonists; D000806:Angiotensin-Converting Enzyme Inhibitors