title: Simultaneous endocardial mapping in the human left ventricle using a noncontact catheter: comparison of contact and reconstructed electrograms during sinus rhythm.
abstract: BACKGROUND
  Catheter ablation of ventricular tachycardia is limited in part by difficulty in identifying suitable sites for ablation. A noncontact multielectrode array (MEA) has been developed that allows reconstruction of 3360 electrograms, using inverse-solution mathematics, that are superimposed onto a computer-simulated model of the endocardium. This study assesses the accuracy of timing and morphology of reconstructed unipolar electrograms compared with contact unipolar electrograms from the same endocardial site.
  
  
  RESULTS
  The MEA was deployed in the left ventricles of 13 patients (end-diastolic diameters, 61.7+/-8.4 mm [mean+/-SD]). We recorded contact electrograms at 76 points equatorial and 32 points nonequatorial to the MEA during sinus rhythm using a catheter-locator signal to record direction and distance from the MEA. Morphology (cross-correlation) and timing of maximum -dV/dt of contact and reconstructed electrograms were compared at different distances from the MEA center to endocardium (M-E) and from the MEA equatorial plane. For equatorial data, the M-E was 32.12+/-12.12 mm. The timing of reconstructed with respect to contact electrograms was -1.94+/-7.12 ms for M-E <34 mm and -14.16+/-19.29 ms at M-E >34 mm (P<0.001). Cross-correlation of electrograms was 0.87+/-0.12 (95% CI, 0.84 to 0.91) and 0.76+/-0.18 (95% CI, 0.69 to 0.83) for M-E <34 mm and >34 mm, respectively. Nonequatorial points were 32.33+/-10.81 mm (range, 16.9 to 55.6 mm) from the MEA equatorial plane; electrogram timing difference was -8.97+/-15.75 ms and was unrelated to this distance from the equator.
  
  
  CONCLUSIONS
  This noncontact mapping system accurately reconstructs endocardial unipolar electrograms from the human left ventricle. At M-E distances >34 mm, timing accuracy of reconstruction decreases.
authors.affiliation: St Mary's Hospital and Imperial College School of Medicine, London, UK.
authors.forename: R J
authors.initials: RJ
authors.lastname: Schilling
authors.forename: N S
authors.initials: NS
authors.lastname: Peters
authors.forename: D W
authors.initials: DW
authors.lastname: Davies
mesh_terms: D000328:Adult; D000368:Aged; D017115:Catheter Ablation / Q000295:instrumentation* / Q000379:methods*; D004562:Electrocardiography; D004566:Electrodes; D004699:Endocardium / Q000503:physiopathology; D005260:Female; D006329:Heart Conduction System / Q000503:physiopathology; D006801:Humans; D007091:Image Processing, Computer-Assisted; D008297:Male; D008875:Middle Aged; D013610:Tachycardia / Q000175:diagnosis* / Q000503:physiopathology* / Q000601:surgery; D016277:Ventricular Function, Left