title: Estimation of atrial response to entrainment pacing using electrograms recorded from remote sites.
abstract: BACKGROUND
  Assessing the entrainment response by measuring postpacing intervals (PPIs) at the pacing site facilitates localization of reentrant circuits, but may be technically difficult.
  
  
  RESULTS
  There were 269 right atrial sites entrained in 21 circuits in congenital heart patients left atrial (LA) electrograms were recorded. Entrainment response was measured by two methods: (1) PPI-tachycardia cycle length, and (2) the difference in latencies between the stimulus artifact and the pacing site electrogram, referenced to the LA electrogram. PPI also was measured from the LA as an index of antidromic activation. Among 43 pacing sites with antidromic LA activation, half showed a discrepancy 225 msec between methods 1 and 2. At the other 226 sites, agreement between the two methods was high (mean discrepancy -3+/-8 msec, r = 0.975, 0 sites with discrepancy 225 msec). Correcting all sites by LA antidromicity reduced the mean discrepancy to +1+/-6 msec and improved correlation (r = 0.988).
  
  
  CONCLUSIONS
  LA electrograms can be used to estimate right atrial entrainment response, if antidromic activation of the LA is recognized and taken into account.
authors.affiliation: Department of Cardiology, Children's Hospital, Boston, Massachusetts 02115, USA. triedman@cardio.tch.harvard.edu
authors.forename: J K
authors.initials: JK
authors.lastname: Triedman
authors.forename: M E
authors.initials: ME
authors.lastname: Alexander
authors.forename: C I
authors.initials: CI
authors.lastname: Berul
authors.forename: L M
authors.initials: LM
authors.lastname: Bevilacqua
authors.forename: E P
authors.initials: EP
authors.lastname: Walsh
mesh_terms: D000293:Adolescent; D000328:Adult; D002304:Cardiac Pacing, Artificial; D002648:Child; D002675:Child, Preschool; D004594:Electrophysiology; D006321:Heart / Q000503:physiopathology*; D006325:Heart Atria; D006331:Heart Diseases / Q000151:congenital* / Q000503:physiopathology*; D006801:Humans; D008875:Middle Aged; D011930:Reaction Time; D013610:Tachycardia / Q000503:physiopathology