title: Comparison of fast Fourier transform and autoregressive spectral analysis for the study of heart rate variability in diabetic patients.
abstract: BACKGROUND
  Impaired heart rate variability (HRV) is associated with poor outcome in diabetic patients. The present prospective study compared spectral components of HRV obtained by either fast Fourier transform (FFT) or autoregressive (AR) analyses in diabetic patients.
  
  
  METHODS
  Thirty patients (49+/-12 years; 11 F/19 M; 60% with insulin-dependent type 1 diabetes) underwent 24-h ambulatory electrocardiographic recordings which comprised a 10-min resting period at the onset (n=30) and end (n=12) of the monitoring. Spectral analysis was applied to 5-min sequences at rest, and the total power and power spectra integrated over the very low (VLF), low (LF), and high (HF) frequency bands were obtained.
  
  
  RESULTS
  Fifteen patients had moderately depressed HRV and two patients had highly depressed HRV (standard deviation of the RR intervals over 24-h<100 ms and <50 ms, respectively). Both raw data and ln-transformed data were significantly different between FFT and AR. All spectra component were obtained in each patient using FFT. Using AR, the LF/HF ratio could not be estimated or was zero in 4 and 11 patients, respectively. The AR results were more sensitive than FFT results to minor changes (+/-5%) in the timing of the onset of analysis. The day-to-day reproducibility of FFT was better than that of AR. Finally, using FFT, the LF/HF ratio, LFnu, and HFnu were essentially redundant (nu=normalized units).
  
  
  CONCLUSIONS
  The spectral components of short-term HRV calculated by using the FFT and AR methods were not interchangeable and FFT analysis must be preferred in diabetic patients.
authors.affiliation: Service de Physiologie Cardio-Respiratoire and Service d'Endocrinologie, Centre Hospitalo-Universitaire de Bicêtre, Assistance Publique-Hopitaux de Paris, Université Paris Sud 11, 94 275 Le Kremlin Bicêtre, France. denis.chemla@bct.ap-hop-paris.fr
authors.forename: Denis
authors.initials: D
authors.lastname: Chemla
authors.forename: Jacques
authors.initials: J
authors.lastname: Young
authors.forename: Fabio
authors.initials: F
authors.lastname: Badilini
authors.forename: Pierre
authors.initials: P
authors.lastname: Maison-Blanche
authors.forename: Hélène
authors.initials: H
authors.lastname: Affres
authors.forename: Yves
authors.initials: Y
authors.lastname: Lecarpentier
authors.forename: Philippe
authors.initials: P
authors.lastname: Chanson
mesh_terms: D000328:Adult; D002940:Circadian Rhythm / Q000502:physiology; D003922:Diabetes Mellitus, Type 1 / Q000503:physiopathology*; D015716:Electrocardiography, Ambulatory; D005260:Female; D005583:Fourier Analysis; D006329:Heart Conduction System / Q000503:physiopathology; D006339:Heart Rate / Q000502:physiology*; D006801:Humans; D008297:Male; D008875:Middle Aged; D015999:Multivariate Analysis; D011446:Prospective Studies; D015203:Reproducibility of Results