title: Computational method for high resolution spectral analysis of fractionated atrial electrograms.
abstract: BACKGROUND
  The discrete Fourier transform (DFT) is often used as a spectral estimator for analysis of complex fractionated atrial electrograms (CFAE) acquired during atrial fibrillation (AF). However, time resolution can be unsatisfactory, as the frequency resolution is proportional to rate/time interval. In this study we compared the DFT to a new spectral estimator with improved time-frequency resolution.
  
  
  METHODS
  Recently, a novel spectral estimator (NSE) based upon signal averaging was derived and implemented computationally. The NSE is similar to the DFT in that both estimators model the autocorrelation function to form the power spectrum. However, as derived in this study, NSE frequency resolution is proportional to rate/period(2) and thus unlike the DFT, is not directly dependent on the window length. We hypothesized that the NSE would provide improved time resolution while maintaining satisfactory frequency resolution for computation of CFAE spectral parameters. Window lengths of 8s, 4s, 2s, 1s, and 0.5s were used for analysis. Two criteria gauged estimator performance. Firstly, a periodic electrogram pattern with phase jitter was embedded in interference. The error in detecting the frequency of the periodic pattern was determined. Secondly, significant differences in spectral parameters for paroxysmal versus persistent AF data, which have known dissimilarities, were determined using the DFT versus NSE methods. The parameters measured were the dominant amplitude, dominant frequency, and mean spectral profile.
  
  
  RESULTS
  At all time resolutions, the error in detecting the frequency of the repeating electrogram pattern was less for NSE than for DFT (p<0.001). The DFT was accurate to 2s time resolution/0.5 Hz frequency resolution, while the NSE was accurate to 0.5s time resolution/0.05 Hz frequency resolution. At all time resolutions, significant differences in the dominant amplitude spectral parameter for paroxysmal versus persistent CFAE were greater using NSE than DFT (p<0.0001). For three of five time resolutions, the NSE had greater significant differences than DFT for discriminating the dominant frequency and mean spectral profile parameters between AF types.
  
  
  CONCLUSIONS
  The results suggest that the NSE has improved performance versus DFT for measurement of CFAE spectral properties.
authors.affiliation: Department of Medicine-Division of Cardiology Columbia University Medical Center, 630 West 168th Street, New York, NY, USA. Electronic address: ciaccio@columbia.edu.
authors.forename: Edward J
authors.initials: EJ
authors.lastname: Ciaccio
authors.forename: Angelo B
authors.initials: AB
authors.lastname: Biviano
authors.forename: Hasan
authors.initials: H
authors.lastname: Garan
mesh_terms: D001281:Atrial Fibrillation / Q000503:physiopathology; D022062:Electrophysiologic Techniques, Cardiac / Q000379:methods*; D005583:Fourier Analysis; D006325:Heart Atria / Q000503:physiopathology; D006801:Humans
keywords: Atrial fibrillation; Dominant frequency; Ensemble averaging; Fourier analysis; Spectral estimation