title: Spatial resolution of pace mapping of idiopathic ventricular tachycardia/ectopy originating in the right ventricular outflow tract.
abstract: BACKGROUND
  Pace mapping has been used to identify the site of origin of focal ventricular arrhythmias. The spatial resolution of pace mapping has not been adequately quantified using currently available three-dimensional mapping systems.
  
  
  OBJECTIVE
  The purpose of this study was to determine the spatial resolution of pace mapping in patients with idiopathic ventricular tachycardia or premature ventricular contractions originating in the right ventricular outflow tract.
  
  
  METHODS
  In 16 patients with idiopathic ventricular tachycardia/ectopy from the right ventricular outflow tract, comparisons and classifications of pace maps were performed by two observers (good pace map: match >10/12 leads; inadequate pace map: match < or =10/12 leads) and a customized MATLAB 6.0 program (assessing correlation coefficient and normalized root mean square of the difference (nRMSd) between test and template signals). With an electroanatomic mapping system, the correlation coefficient of each pace map was correlated with the distance between the pacing site and the effective ablation site. The endocardial area within the 10-ms activation isochrone was measured.
  
  
  RESULTS
  The ablation procedure was effective in all patients. Sites with good pace maps had a higher correlation coefficient and lower nRMSd than sites with inadequate pace maps (correlation coefficient: 0.96 +/- 0.03 vs 0.76 +/- 0.18, P <.0001; nRMSd: 0.41 +/- 0.16 vs 0.89 +/- 0.39, P <.0001). Using receiver operating characteristic curves, appropriate cutoff values were >0.94 for correlation coefficient (sensitivity 81%, specificity 89%) and < or =0.54 for nRMSd (sensitivity 76%, specificity 80%). Good pace maps were located a mean of 7.3 +/- 5.0 mm from the effective ablation site and had a mean activation time of -24 +/- 7 ms. However, in 3 (18%) of 16 patients, the best pace map was inadequate at the effective ablation site, with an endocardial activation time at these sites of -25 +/- 12 ms. Pace maps with correlation coefficient > or =0.94 were confined to an area of 1.8 +/- 0.6 cm2. The 10-ms isochrone measured 1.2 +/- 0.7 cm2.
  
  
  CONCLUSIONS
  The spatial resolution of a good pace map for targeting ventricular tachycardia/ectopy is 1.8 cm2 in the right ventricular outflow tract and therefore is inferior to the spatial resolution of activation mapping as assessed by isochronal activation. In approximately 20% of patients, pace mapping is unreliable in identifying the site of origin, possibly due a deeper site of origin and preferential conduction via fibers connecting the focus to the endocardial surface.
authors.affiliation: University of Michigan Medical Center, Ann Arbor, MI 48109-0366, USA. fbogun@umich.edu <fbogun@umich.edu>
authors.forename: Frank
authors.initials: F
authors.lastname: Bogun
authors.forename: Majid
authors.initials: M
authors.lastname: Taj
authors.forename: Michael
authors.initials: M
authors.lastname: Ting
authors.forename: Hyungjin Myra
authors.initials: HM
authors.lastname: Kim
authors.forename: Stephen
authors.initials: S
authors.lastname: Reich
authors.forename: Eric
authors.initials: E
authors.lastname: Good
authors.forename: Krit
authors.initials: K
authors.lastname: Jongnarangsin
authors.forename: Aman
authors.initials: A
authors.lastname: Chugh
authors.forename: Frank
authors.initials: F
authors.lastname: Pelosi
authors.forename: Hakan
authors.initials: H
authors.lastname: Oral
authors.forename: Fred
authors.initials: F
authors.lastname: Morady
mesh_terms: D002304:Cardiac Pacing, Artificial; D017115:Catheter Ablation; D016009:Chi-Square Distribution; D004562:Electrocardiography; D022062:Electrophysiologic Techniques, Cardiac / Q000379:methods*; D004699:Endocardium / Q000503:physiopathology*; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D012372:ROC Curve; D017180:Tachycardia, Ventricular / Q000503:physiopathology* / Q000601:surgery; D018497:Ventricular Dysfunction, Right / Q000503:physiopathology* / Q000601:surgery; D014694:Ventricular Outflow Obstruction / Q000503:physiopathology* / Q000601:surgery; D018879:Ventricular Premature Complexes / Q000503:physiopathology* / Q000601:surgery