title: Novel spectral indexes of heart rate variability as predictors of sudden and non-sudden cardiac death after an acute myocardial infarction.
abstract: BACKGROUND
  Various indexes of 24-hour heart rate variability (HRV) have been able to predict all-cause mortality after an acute myocardial infarction (AMI), but their value in predicting specific modes of cardiac death has been limited.
  
  
  OBJECTIVE
  The aim of this study was to assess the role of two novel spectral indexes of HRV as predictors of either sudden (SCD) or non-sudden cardiac death after an AMI. Method. We used two novel methods of spectral analysis of HRV: 1) the high-frequency (HF) spectral component, V(index), calculated as an average HF power from the most linear portion of HF power versus the R-R interval regression curve, and 2) the prevalent low-frequency oscillation of heart rate (PLF). V(index), conventional HRV measures, and PLF were analyzed from 24-hour Holter recordings of 590 patients with a recent AMI.
  
  
  RESULTS
  During the mean follow-up of 39+/-14 months, SCD occurred in 3% (n = 17) and non-sudden cardiac death in 5% (n = 28) of the patients. In univariate analysis, V(index) was the most potent predictor of SCD (RR: 6.0, 95% CI: 1.7-20.7, P<0.01), also remaining the most powerful predictor of SCD after adjustment for clinical variables and ejection fraction (RR: 4.2, 95% CI: 1.2-15.2, P<0.05). PLF was a potent predictor of non-sudden cardiac death (RR: 13.9, 95% CI: 5.9-32.5, P<0.001), but it did not predict SCD.
  
  
  CONCLUSIONS
  Novel spectral HRV analysis methods, V(index) and PLF, provide significant information of the risk of the specific mode of death after an AMI.
authors.affiliation: Merikoski Rehabilitation and Research Centre, Oulu, Finland.
authors.forename: Antti M
authors.initials: AM
authors.lastname: Kiviniemi
authors.forename: Mikko P
authors.initials: MP
authors.lastname: Tulppo
authors.forename: Dan
authors.initials: D
authors.lastname: Wichterle
authors.forename: Arto J
authors.initials: AJ
authors.lastname: Hautala
authors.forename: Suvi
authors.initials: S
authors.lastname: Tiinanen
authors.forename: Tapio
authors.initials: T
authors.lastname: Seppänen
authors.forename: Timo H
authors.initials: TH
authors.lastname: Mäkikallio
authors.forename: Heikki V
authors.initials: HV
authors.lastname: Huikuri
mesh_terms: D002940:Circadian Rhythm / Q000502:physiology*; D016757:Death, Sudden, Cardiac / Q000453:epidemiology* / Q000209:etiology; D004452:Echocardiography; D004562:Electrocardiography; D005260:Female; D005387:Finland / Q000453:epidemiology; D005500:Follow-Up Studies; D006339:Heart Rate / Q000502:physiology*; D006801:Humans; D008297:Male; D008875:Middle Aged; D009203:Myocardial Infarction / Q000000981:diagnostic imaging / Q000401:mortality* / Q000503:physiopathology; D011379:Prognosis; D012189:Retrospective Studies; D015996:Survival Rate; D013997:Time Factors; D014630:Vagus Nerve / Q000503:physiopathology; D016277:Ventricular Function, Left / Q000502:physiology