title: Dynamic analysis of cardiac rhythms for discriminating atrial fibrillation from lethal ventricular arrhythmias.
abstract: BACKGROUND
  Implantable cardioverter-defibrillators (ICDs), the first line of therapy for preventing sudden cardiac death in high-risk patients, deliver appropriate shocks for termination of ventricular tachycardia (VT)/ventricular fibrillation. A common shortcoming of ICDs is imperfect rhythm discrimination, resulting in the delivery of inappropriate shocks for atrial fibrillation (AF). An underexplored area for rhythm discrimination is the difference in dynamic properties between AF and VT/ventricular fibrillation. We hypothesized that the higher entropy of rapid cardiac rhythms preceding ICD shocks distinguishes AF from VT/ventricular fibrillation.
  
  
  RESULTS
  In a multicenter, prospective, observational study of patients with primary prevention ICDs, 119 patients received shocks from ICDs with stored, retrievable intracardiac electrograms. Blinded adjudication revealed shocks were delivered for VT/ventricular fibrillation (62%), AF (23%), and supraventricular tachycardia (15%). Entropy estimation of only 9 ventricular intervals before ICD shocks accurately distinguished AF (receiver operating characteristic curve area, 0.98; 95% confidence intervals, 0.93-1.0) and outperformed contemporary ICD rhythm discrimination algorithms.
  
  
  CONCLUSIONS
  This new strategy for AF discrimination based on entropy estimation expands on simpler concepts of variability, performs well at fast heart rates, and has potential for broad clinical application.
authors.affiliation: Division of Cardiology, Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA. Deep@jhmi.edu
authors.forename: Deeptankar
authors.initials: D
authors.lastname: DeMazumder
authors.forename: Douglas E
authors.initials: DE
authors.lastname: Lake
authors.forename: Alan
authors.initials: A
authors.lastname: Cheng
authors.forename: Travis J
authors.initials: TJ
authors.lastname: Moss
authors.forename: Eliseo
authors.initials: E
authors.lastname: Guallar
authors.forename: Robert G
authors.initials: RG
authors.lastname: Weiss
authors.forename: Steven R
authors.initials: SR
authors.lastname: Jones
authors.forename: Gordon F
authors.initials: GF
authors.lastname: Tomaselli
authors.forename: J Randall
authors.initials: JR
authors.lastname: Moorman
mesh_terms: D000328:Adult; D000368:Aged; D001281:Atrial Fibrillation / Q000175:diagnosis* / Q000401:mortality / Q000628:therapy; D016757:Death, Sudden, Cardiac / Q000209:etiology / Q000517:prevention & control*; D017147:Defibrillators, Implantable; D003937:Diagnosis, Differential; D004562:Electrocardiography / Q000379:methods*; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D011446:Prospective Studies; D018570:Risk Assessment; D012720:Severity of Illness Index; D016019:Survival Analysis; D017180:Tachycardia, Ventricular / Q000175:diagnosis / Q000401:mortality / Q000628:therapy; D016896:Treatment Outcome; D014693:Ventricular Fibrillation / Q000175:diagnosis* / Q000401:mortality / Q000628:therapy
keywords: ECG; death, sudden, cardiac; defibrillators, implantable; entropy; inappropriate shock; nonlinear dynamics; tachycardia, ventricular; ventricular fibrillation