title: Validation of the noncontact mapping system in the left atrium during permanent atrial fibrillation and sinus rhythm.
abstract: OBJECTIVE
  The aim of this study was to validate noncontact mapping (NCM) in the left atrium (LA) during sinus rhythm and atrial fibrillation (AF).
  
  
  BACKGROUND
  Understanding the mechanisms of AF is crucial to the development of novel and effective treatments. Noncontact mapping records global electrical activation simultaneously and therefore has the potential to elucidate these mechanisms.
  
  
  METHODS
  Patients underwent catheter ablation of permanent AF guided by NCM. Virtual and contact unipolar electrograms were recorded simultaneously during sinus rhythm and AF from sites spanning the LA and their morphology, amplitude, and timing were compared. The impact of distance from the array to the endocardial surface and electrogram amplitude were analyzed.
  
  
  RESULTS
  A total of 22 patients age 52 +/- 9 (mean +/- SD) years were studied. During sinus rhythm, the median (range) morphology correlation and timing difference between contact and virtual atrial electrograms were 0.81 (0.27 to 0.98) and 4.2 (0 to 18.3) ms, respectively. These results were significantly worse than the corresponding far field individual ventricular electrograms; 0.91 (0.53 to 1.0) and 1.7 (0 to 18.3) ms (p < 0.001). For endocardial sites >40 mm from the array, the correlation was significantly worse than sites <40 mm: 0.73 (0.48 to 0.95) versus 0.87 (0.27 to 0.98) (p < 0.001). The correlation during AF was 0.72 (0.24 to 0.98), which deteriorated with increasing distance from the array. In the presence of adenosine induced atrioventricular block the correlation deteriorated 0.67 +/- 0.16 versus 0.79 +/- 0.11 (p < 0.001).
  
  
  CONCLUSIONS
  Noncontact mapping can be performed in human LA; however, the accuracy of reconstructed electrograms is poor >40 mm from the center of the array, particularly during AF. Care must be taken interpreting isopotential maps if the entire endocardial surface of the LA is not close to the array.
authors.affiliation: Department of Cardiology, St. Bartholomew's Hospital, London, United Kingdom.
authors.forename: Mark J
authors.initials: MJ
authors.lastname: Earley
authors.forename: Dominic J R
authors.initials: DJ
authors.lastname: Abrams
authors.forename: Simon C
authors.initials: SC
authors.lastname: Sporton
authors.forename: Richard J
authors.initials: RJ
authors.lastname: Schilling
mesh_terms: D000241:Adenosine; D000328:Adult; D001281:Atrial Fibrillation / Q000175:diagnosis* / Q000503:physiopathology*; D016279:Atrial Function, Left; D022062:Electrophysiologic Techniques, Cardiac / Q000592:standards*; D005260:Female; D006327:Heart Block / Q000139:chemically induced / Q000503:physiopathology; D006339:Heart Rate; D006801:Humans; D008297:Male; D008875:Middle Aged; D014584:User-Computer Interface
chemical_list: D000241:Adenosine