title: Automatic online detection of atrial fibrillation based on symbolic dynamics and Shannon entropy.
abstract: BACKGROUND
  Atrial fibrillation (AF) is the most common and debilitating abnormalities of the arrhythmias worldwide, with a major impact on morbidity and mortality. The detection of AF becomes crucial in preventing both acute and chronic cardiac rhythm disorders.
  
  
  OBJECTIVE
  Our objective is to devise a method for real-time, automated detection of AF episodes in electrocardiograms (ECGs). This method utilizes RR intervals, and it involves several basic operations of nonlinear/linear integer filters, symbolic dynamics and the calculation of Shannon entropy. Using novel recursive algorithms, online analytical processing of this method can be achieved.
  
  
  RESULTS
  Four publicly-accessible sets of clinical data (Long-Term AF, MIT-BIH AF, MIT-BIH Arrhythmia, and MIT-BIH Normal Sinus Rhythm Databases) were selected for investigation. The first database is used as a training set; in accordance with the receiver operating characteristic (ROC) curve, the best performance using this method was achieved at the discrimination threshold of 0.353: the sensitivity (Se), specificity (Sp), positive predictive value (PPV) and overall accuracy (ACC) were 96.72%, 95.07%, 96.61% and 96.05%, respectively. The other three databases are used as testing sets. Using the obtained threshold value (i.e., 0.353), for the second set, the obtained parameters were 96.89%, 98.25%, 97.62% and 97.67%, respectively; for the third database, these parameters were 97.33%, 90.78%, 55.29% and 91.46%, respectively; finally, for the fourth set, the Sp was 98.28%. The existing methods were also employed for comparison.
  
  
  CONCLUSIONS
  Overall, in contrast to the other available techniques, the test results indicate that the newly developed approach outperforms traditional methods using these databases under assessed various experimental situations, and suggest our technique could be of practical use for clinicians in the future.
authors.affiliation: Institute of Biomedical and Health Engineering, Shenzhen Institutes of Advanced Technology, Chinese Academy of Sciences, Xili Nanshan, Shenzhen 518055, China. xl.zhou@siat.ac.cn.
authors.forename: Xiaolin
authors.initials: X
authors.lastname: Zhou
authors.forename: Hongxia
authors.initials: H
authors.lastname: Ding
authors.forename: Benjamin
authors.initials: B
authors.lastname: Ung
authors.forename: Emma
authors.initials: E
authors.lastname: Pickwell-MacPherson
authors.forename: Yuanting
authors.initials: Y
authors.lastname: Zhang
mesh_terms: D000465:Algorithms; D001281:Atrial Fibrillation / Q000175:diagnosis*; D003936:Diagnosis, Computer-Assisted; D004562:Electrocardiography; D001330:Electronic Data Processing; D019277:Entropy; D006801:Humans; D009862:Online Systems; D012372:ROC Curve; D012984:Software