title: New method of determining the atrial fibrillation cycle length during human atrial fibrillation.
abstract: BACKGROUND
  The aim of this study was to investigate the usefulness of the autocorrelation function (reversed fast Fourier transform analysis) in determining the atrial fibrillation cycle length (AFCL) during human atrial fibrillation (AF).
  
  
  RESULTS
  From 30 episodes of atrial electrograms recorded for 30 seconds from the high right atrium during type I AF in 16 patients, the mean, 5th percentile (p5), and 95th percentile (p95) of the AFCLs were measured by using a computer-picked activation time. The peak, minimum, and maximum AFCLs also were measured by using the autocorrelation function. The mean AFCL was retrieved at the point of the maximum peak of the coefficient of the first positive autocorrelogram. The minimum AFCL (min AFCL) was chosen as the point where the first positive autocorrelogram crossed the baseline from negative to positive, and the maximum AFCL (max AFCL) was chosen as the point where the first positive autocorrelogram crossed the baseline from positive to negative. There was a significantly strong correlation between the mean and peak AFCLs (r = 0.995, P < 0.0001), p5 and min AFCLs (r = 0.953, P < 0.0001), and p95 and max AFCLs (r = 0.98, P < 0.0001).
  
  
  CONCLUSIONS
  The autocorrelation function was useful in determining the AFCLs, at least during type I AF. The min AFCL may be used as an index of the refractory period during AF when the p5 AFCL approximates the refractory period.
authors.affiliation: Faculty of Health Sciences, Yamaguchi University School of Medicine, 1-1-1 Minami-kogushi, Ube, Yamaguchi, Japan 755-8505. ashimizu@yamaguchi-u.ac.jp
authors.forename: Akihiko
authors.initials: A
authors.lastname: Shimizu
authors.forename: Toshihiko
authors.initials: T
authors.lastname: Yamagata
authors.forename: Masahiro
authors.initials: M
authors.lastname: Esato
authors.forename: Masahiro
authors.initials: M
authors.lastname: Doi
authors.forename: Hiroyuki
authors.initials: H
authors.lastname: Kakugawa
authors.forename: Ryousuke
authors.initials: R
authors.lastname: Kametani
authors.forename: Noriko
authors.initials: N
authors.lastname: Inoue
authors.forename: Masashi
authors.initials: M
authors.lastname: Kanemoto
authors.forename: Masunori
authors.initials: M
authors.lastname: Matsuzaki
mesh_terms: D000368:Aged; D001281:Atrial Fibrillation / Q000503:physiopathology*; D022062:Electrophysiologic Techniques, Cardiac; D005260:Female; D005583:Fourier Analysis; D006321:Heart / Q000503:physiopathology*; D006801:Humans; D008297:Male; D008875:Middle Aged; D012032:Refractory Period, Electrophysiological; D013997:Time Factors