title: Impedance monitoring during catheter ablation of atrial fibrillation.
abstract: BACKGROUND
  Delivery of radiofrequency energy in proximity of a pulmonary vein can cause vein stenosis. A sudden decrease in impedance as the catheter is moved from the vein into the left atrium (LA) has been used to define the pulmonary vein-LA transition during ablation procedures.
  
  
  OBJECTIVE
  The purpose of this study was to define the variables affecting impedance measurement.
  
  
  METHODS
  In vitro analysis of impedance was performed in a saline bath using sheaths and a plastic stereolithographic model of the LA. Impedance was continuously monitored during a calibrated pullback from the pulmonary vein into the LA in 37 veins of 10 patients referred for catheter ablation. Location of the catheter was confirmed by the following imaging modalities: intracardiac echocardiography, contrast venography, electroanatomic mapping, and computed tomography/magnetic resonance imaging (offline) in all patients.
  
  
  RESULTS
  Larger cross-sectional areas containing the catheter correlated with lower impedance in an exponential manner both with respect to sheath size (R(2) = 0.99) and in the stereolithographic model (R(2) = 0.91). In vivo, the impedance in the pulmonary veins decreased in an exponential manner as the catheter was pulled back into the LA. However, impedance at the vein orifice was not significantly higher than the LA. A defined cutoff value for defining the pulmonary vein-LA transition could not be identified.
  
  
  CONCLUSIONS
  The primary determinant of impedance is the cross-sectional area of the space containing the catheter. Impedance monitoring alone does not guarantee a catheter tip position outside the pulmonary vein. Intraprocedural imaging confirmation should be considered to avoid radiofrequency application within pulmonary veins.
authors.affiliation: UCLA Cardiac Arrhythmia Center, Division of Cardiology, Department of Medicine, David Geffen School of Medicine at UCLA, Los Angeles, California 90095, USA.
authors.forename: Marmar
authors.initials: M
authors.lastname: Vaseghi
authors.forename: David A
authors.initials: DA
authors.lastname: Cesario
authors.forename: Miguel
authors.initials: M
authors.lastname: Valderrabano
authors.forename: Noel G
authors.initials: NG
authors.lastname: Boyle
authors.forename: Osman
authors.initials: O
authors.lastname: Ratib
authors.forename: J Paul
authors.initials: JP
authors.lastname: Finn
authors.forename: Isaac
authors.initials: I
authors.lastname: Wiener
authors.forename: Kalyanam
authors.initials: K
authors.lastname: Shivkumar
mesh_terms: D000368:Aged; D001281:Atrial Fibrillation / Q000175:diagnosis / Q000503:physiopathology* / Q000601:surgery*; D016275:Atrial Function; D017115:Catheter Ablation; D004452:Echocardiography; D017097:Electric Impedance; D022062:Electrophysiologic Techniques, Cardiac; D005260:Female; D005471:Fluoroscopy; D006325:Heart Atria / Q000503:physiopathology; D006801:Humans; D015141:Los Angeles; D008279:Magnetic Resonance Imaging; D008297:Male; D008875:Middle Aged; D011667:Pulmonary Veins / Q000503:physiopathology; D012107:Research Design; D014057:Tomography, X-Ray Computed; D016896:Treatment Outcome; D018754:Ventricular Dysfunction / Q000503:physiopathology / Q000601:surgery