title: Temporal changes and prognostic significance of measures of heart rate dynamics after acute myocardial infarction in the beta-blocking era.
abstract: Previous studies have shown that indexes describing heart rate (HR) dynamics may predict subsequent deaths of patients after an acute myocardial infarction (AMI). Because beta-blocking (BB) drugs affect both mortality and HR dynamics, the prognostic power of measurements of HR dynamics may have changed in the current era of BB therapy. This study assessed the temporal changes and prognostic significance of time-domain, spectral, and fractal indexes of HR variability along with HR turbulence after an AMI among patients with optimized BB medication. SD of NN intervals, spectral indexes, the short-term fractal scaling exponent (alpha(1)), power-law slope (beta), and turbulence onset and slope were measured in 600 patients at 5 to 7 days after AMI and in 416 patients at 12 months after AMI. In the multivariate analysis, after adjusting for clinical variables, only reduced fractal HR indexes, alpha1 and beta (p <0.01 for both), turbulence onset, and slope (p <0.05 for both), measured at the convalescent phase after AMI, predicted subsequent cardiac death. All time-domain and spectral HR variability indexes and turbulence onset increased significantly during the 12-month period after AMI (p <0.001 for all), whereas the fractal indexes and turbulence slope remained unchanged. Late after AMI, reduced beta (p <0.05) and turbulence slope (p <0.01) were the only independent predictors of cardiac mortality. Traditional time-domain and spectral measurements of HR variability and turbulence onset improved significantly after AMI, whereas the fractal HR dynamics and turbulence slope remained stable. Fractal HR variability and HR turbulence retain their prognostic power in the BB era, when measured either at the convalescent or late phase after AMI.
authors.affiliation: Division of Cardiology, Department of Medicine, University of Oulu, Oulu, Finland. vesa.jokinen@oulu.fi
authors.forename: Vesa
authors.initials: V
authors.lastname: Jokinen
authors.forename: Jari M
authors.initials: JM
authors.lastname: Tapanainen
authors.forename: Tapio
authors.initials: T
authors.lastname: Seppänen
authors.forename: Heikki V
authors.initials: HV
authors.lastname: Huikuri
mesh_terms: D000208:Acute Disease; D000319:Adrenergic beta-Antagonists / Q000627:therapeutic use*; D000368:Aged; D004452:Echocardiography; D005260:Female; D017709:Fractals; D006339:Heart Rate / Q000502:physiology*; D006801:Humans; D008297:Male; D008875:Middle Aged; D015233:Models, Statistical; D015999:Multivariate Analysis; D009203:Myocardial Infarction / Q000188:drug therapy* / Q000401:mortality* / Q000503:physiopathology; D017711:Nonlinear Dynamics; D011237:Predictive Value of Tests; D011379:Prognosis; D016016:Proportional Hazards Models; D011446:Prospective Studies; D016019:Survival Analysis
chemical_list: D000319:Adrenergic beta-Antagonists