title: Fractal scaling properties of heart rate dynamics and myocardial efficiency in dilated cardiomyopathy.
abstract: BACKGROUND
  Since altered heart rate (HR) fluctuations provide prognostic information in heart failure, we examined the associations between HR dynamics, myocardial efficiency and perfusion, among patients with dilated cardiomyopathy.
  
  
  METHODS
  Sixteen patients with dilated cardiomyopathy were enrolled. Patients received supervised strength and aerobic training for 5 months (n = 9) or standard care (n = 7). The short-term scaling exponent (alpha(1)) and frequency domain measures of HR behavior were assessed at baseline and after 5 months of intervention. The left ventricular (LV) function measured using echocardiography and oxidative metabolism measured using positron emission tomography (PET) and [(11)C]-acetate were used to estimate the myocardial efficiency.
  
  
  RESULTS
  Short-term fractal exponent alpha(1) correlated significantly with LV myocardial efficiency (r = 0.77, p = 0.002) at baseline. After the intervention period, the majority of patients showed improved myocardial efficiency and small or marked change in HR dynamics toward the natural fractal-like organization (alpha(1) value close 1). Parallel change in fractal properties of HR and myocardial efficiency after intervention was observed in 78% of the patients. Intervention had no significant effect on any other HR fluctuation indices.
  
  
  CONCLUSIONS
  The present study suggests that short-term fractal scaling exponent alpha(1), an important prognostic marker in heart failure, is related to LV myocardial efficiency.
authors.affiliation: Department of Medicine, University of Turku, 20520 Turku, Finland. tiina.salo@tyks.fi
authors.forename: Tiina Marjatta
authors.initials: TM
authors.lastname: Salo
authors.forename: Jan
authors.initials: J
authors.lastname: Sundell
authors.forename: Juhani
authors.initials: J
authors.lastname: Knuuti
authors.forename: Jukka
authors.initials: J
authors.lastname: Kemppainen
authors.forename: Kira
authors.initials: K
authors.lastname: Stolen
authors.forename: Pirjo
authors.initials: P
authors.lastname: Nuutila
authors.forename: Timo H
authors.initials: TH
authors.lastname: Mäkikallio
authors.forename: Heikki V
authors.initials: HV
authors.lastname: Huikuri
authors.forename: K E Juhani
authors.initials: KE
authors.lastname: Airaksinen
mesh_terms: D002311:Cardiomyopathy, Dilated / Q000175:diagnosis / Q000503:physiopathology* / Q000628:therapy; D004452:Echocardiography; D005081:Exercise Therapy / Q000379:methods*; D005260:Female; D017709:Fractals; D006339:Heart Rate; D006801:Humans; D008297:Male; D008875:Middle Aged; D049268:Positron-Emission Tomography; D011379:Prognosis; D055070:Resistance Training / Q000379:methods; D018487:Ventricular Dysfunction, Left / Q000503:physiopathology*
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