title: Bipolar Intracardiac Electrogram Active Interval Extraction During Atrial Fibrillation.
abstract: We introduce novel methods to identify the active intervals (AIs) of intracardiac electrograms (IEGMs) during complex arrhythmias, such as atrial fibrillation (AF).
  
  
  
  We formulate the AI extraction problem, which consists of estimating the beginning and duration of the AIs, as a sequence of hypothesis tests. In each test, we compare the variance of a small portion of the bipolar IEGM with its adjacent segments. We propose modified general-likelihood ratio (MGLR) and separating-function-estimation tests; we derive five test statistics (TSs), and show that the AIs can be obtained by threshold crossing the TSs. We apply the proposed methods to the IEGM segments collected from the left atrium of 16 patients (62.4 ± 8.2-years old, four females, four paroxysmal, and twelve persistent AF) prior to catheter ablation. The accuracy of our methods is evaluated by comparing them with previously developed methods and manual annotation (MA).
  
  
  
  Our results show a high level of similarity between the AIs of the proposed methods and MA, e.g., the true and false positive rates of one of the MGLR-based methods were, respectively, 97.8% and 1.4%. The mean absolute error from estimation of the onset and end of AIs and also for the estimation of the mean cycle length for that approach was 8.7 ± 10.5, 13 ± 15.5, and 4.2 ± 9.4 ms, respectively.
  
  
  
  The proposed methods can accurately identify onset and duration of AI of the IEGM during AF.
  
  
  
  The proposed methods can be used for real-time automated analysis of AF, the most challenging complex arrhythmia.
authors.forename: Mohammad Hassan
authors.initials: MH
authors.lastname: Shariat
authors.forename: Saeed
authors.initials: S
authors.lastname: Gazor
authors.forename: Damian P
authors.initials: DP
authors.lastname: Redfearn
mesh_terms: D000465:Algorithms; D001281:Atrial Fibrillation / Q000175:diagnosis* / Q000503:physiopathology*; D003936:Diagnosis, Computer-Assisted / Q000379:methods*; D022062:Electrophysiologic Techniques, Cardiac / Q000379:methods*; D005260:Female; D006329:Heart Conduction System; D006801:Humans; D016013:Likelihood Functions; D008297:Male; D008875:Middle Aged; D010363:Pattern Recognition, Automated / Q000379:methods*; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity