title: Atrial fibrillation reduces the atrial impedance amplitude during cardiac cycle: a novel detection algorithm to improve recognition of atrial fibrillation in pacemaker patients.
abstract: OBJECTIVE
  In carriers of dual chamber pacemakers and implantable cardioverter-defibrillators (ICD), detection of atrial fibrillation (AF) is crucial for adequate mode switch function and to avoid inappropriate shock delivery. Detection algorithms rely on the atrial rate and on the relationship of atrial to ventricular intracardiac electrograms, but the relative portion of misclassified AF episodes remains high. Although myocardial impedance is a reliable indicator of contraction, little is known about atrial impedance as a marker of atrial arrhythmias. Methods During an electrophysiological study, we investigated the effect of induced AF on impedance at the right atrial free wall (RAFW) and right atrial appendage (RAA) in 20 patients. Using biphasic square-wave pulses (128 Hz, 200 microA/15 micros), impedance changes were recorded during sinus rhythm (SR-1), atrial pacing at 120 beats/min, AF induced by rapid atrial burst pacing, and after spontaneous AF termination (SR-2). Results At the RAA, peak-to-peak impedance amplitude during cardiac cycle (DeltaZ) dropped from 51.7 +/- 35.3 Omega (SR-1) or 49.6 +/- 30.6 Omega (pacing) to 24.6 +/- 22.0 Omega (AF, P< or =0.0005), and subsequently increased to 37.7 +/- 24.7 Omega (SR-2, P < or = 0.0004 v. AF). At the RAFW, DeltaZ changed from 16.2 +/- 15.5 Omega (SR-1) or 13.5 +/- 9.9 Omega (pacing) to 5.9 +/- 4.1 Omega (AF, P < or = 0.003), and to 11.4 +/- 10.7 Omega (SR-2, P < or = 0.015). Given a discrimination threshold of 65%, the sensitivity and the specificity of DeltaZ to detect AF were 79 +/- 18 and 89 +/- 14%, respectively (95% confidence interval).
  
  
  CONCLUSIONS
  AF causes DeltaZ drop in pacemaker and ICD recipients. This impedance based algorithm can be used as an alternative method of AF detection.
authors.affiliation: Universitätsklinikum Freiburg, Medizinische Klinik III, Department of Cardiology and Angiology, Hugstetter Str 55, D-79106, Freiburg, Germany.
authors.forename: Boris
authors.initials: B
authors.lastname: Schmidt
authors.forename: Stefan
authors.initials: S
authors.lastname: Asbach
authors.forename: Oliver
authors.initials: O
authors.lastname: Schweika
authors.forename: Manfred
authors.initials: M
authors.lastname: Zehender
authors.forename: Christoph
authors.initials: C
authors.lastname: Bode
authors.forename: Thomas S
authors.initials: TS
authors.lastname: Faber
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D000465:Algorithms; D001145:Arrhythmias, Cardiac / Q000503:physiopathology* / Q000628:therapy; D001281:Atrial Fibrillation / Q000503:physiopathology* / Q000628:therapy; D001282:Atrial Flutter; D002304:Cardiac Pacing, Artificial; D002404:Catheterization; D017147:Defibrillators, Implantable; D004554:Electric Countershock; D022062:Electrophysiologic Techniques, Cardiac / Q000379:methods*; D004594:Electrophysiology; D005260:Female; D006321:Heart; D006325:Heart Atria / Q000503:physiopathology*; D006801:Humans; D008297:Male; D008875:Middle Aged; D010138:Pacemaker, Artificial; D012680:Sensitivity and Specificity