title: Impact of changing activation sequence on bipolar electrogram amplitude for voltage mapping of left ventricular infarcts causing ventricular tachycardia.
abstract: BACKGROUND
  Wavefront direction is a determinant of bipolar electrogram amplitude that could influence identification of low amplitude regions indicating infarction or scar.
  
  
  METHODS
  To assess the importance of activation sequence on electrogram amplitude 11 patients with prior infarction and ventricular tachycardia were studied. At 819 left ventricular sites bipolar electrograms were recorded during atrial pacing and ventricular pacing, followed by unipolar pacing with a stimulus of 10 mA at 2 ms. Sites with a pacing threshold > 10 mA were designated electrically unexcitable scar.
  
  
  RESULTS
  Areas of low voltage (< or =1.5 mV) were present in all patients. Atrial paced and ventricular paced electrogram amplitudes were strongly correlated (r = 0.77; P < 0.0001). Changing the activation sequence (from atrial pacing to ventricular pacing) produced a > 50% change in electrogram amplitude at 28% of sites and a > 100% change at 10% of sites, but only 8% of sites had an electrogram amplitude classified as abnormal (< or =1.5 mV) with one activation sequence and normal (> 1.5 mV) with the other activation sequence. Electrically unexcitable scar (6% of sites) was associated with lower electrogram amplitude but could not be reliably identified based on electrogram amplitude alone for either activation sequence.
  
  
  CONCLUSIONS
  Voltage maps created with bipolar recordings using these methods should be relatively robust depictions of abnormal ventricular regions despite variable catheter orientation and activation sequences that might be produced by different rhythms.
authors.affiliation: Cardiovascular Center, University Hospital Zurich, Switzerland. corinna.brunckhorst@usz.ch
authors.forename: Corinna B
authors.initials: CB
authors.lastname: Brunckhorst
authors.forename: Etienne
authors.initials: E
authors.lastname: Delacretaz
authors.forename: Kyoko
authors.initials: K
authors.lastname: Soejima
authors.forename: William H
authors.initials: WH
authors.lastname: Maisel
authors.forename: Peter L
authors.initials: PL
authors.lastname: Friedman
authors.forename: William G
authors.initials: WG
authors.lastname: Stevenson
mesh_terms: D000368:Aged; D018780:Body Surface Potential Mapping / Q000379:methods*; D006328:Cardiac Catheterization; D002304:Cardiac Pacing, Artificial / Q000379:methods*; D017115:Catheter Ablation; D004562:Electrocardiography; D006329:Heart Conduction System / Q000503:physiopathology; D006801:Humans; D008297:Male; D009203:Myocardial Infarction / Q000150:complications / Q000503:physiopathology*; D011446:Prospective Studies; D017180:Tachycardia, Ventricular / Q000209:etiology / Q000503:physiopathology* / Q000601:surgery
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