title: Sensitivity and specificity of concealed entrainment for the identification of a critical isthmus in the atrium: relationship to rate, anatomic location and antidromic penetration.
abstract: OBJECTIVE
  This study was designed to determine the sensitivity and specificity of concealed entrainment (CE) for the identification of a critical isthmus in the atrium.
  
  
  BACKGROUND
  Isthmus identification during entrainment mapping of macro-reentrant atrial tachycardia (MRAT) relies on the demonstration of CE.
  
  
  METHODS
  Using the model of typical atrial flutter, entrainment was performed in 10 patients at four rates (flutter cycle length [FCL] minus 10/20/30/40 ms) from seven sites: isthmus entrance/exit, low lateral/high lateral/high septal right atrium and proximal/distal coronary sinus. Surface 12-lead electrocardiogram fusion was evaluated by three observers blind to patient status. The extent of antidromic penetration (AP) was measured off the pacing catheter positioned around the tricuspid annulus.
  
  
  RESULTS
  The sensitivity for CE identifying any isthmus site was greatest at FCL-10 (100%), but the specificity was poor (54%). Conversely, specificity was greatest at FCL-40 (98%), but the sensitivity was poor (65%), with manifest entrainment (ME) observed from the isthmus entrance in 70% of episodes. At FCL-30, sensitivity (85%) and specificity (90%) were "balanced," but CE still resulted during entrainment from a non-isthmus site in five of 10 patients. Antidromic penetration increased with pacing CL shortening (p < 0.001) and correlated with the development of ME (p < 0.001). Antidromic penetration was significantly blunted from the isthmus exit compared to all other sites (p = 0.003).
  
  
  CONCLUSIONS
  The sensitivity and specificity of CE for identifying an isthmus in the atrium are critically dependent on the pacing rate and the precise anatomic pacing site within the isthmus. These findings may have implications for the use of entrainment in the mapping of unknown MRAT circuits.
authors.affiliation: Department of Cardiology, The Royal Melbourne Hospital and University of Melbourne, Melbourne, Australia.
authors.forename: Joseph B
authors.initials: JB
authors.lastname: Morton
authors.forename: Prashanthan
authors.initials: P
authors.lastname: Sanders
authors.forename: Vincent
authors.initials: V
authors.lastname: Deen
authors.forename: Jithendra K
authors.initials: JK
authors.lastname: Vohra
authors.forename: Jonathan M
authors.initials: JM
authors.lastname: Kalman
mesh_terms: D000368:Aged; D001282:Atrial Flutter / Q000473:pathology* / Q000503:physiopathology* / Q000628:therapy; D006328:Cardiac Catheterization; D002304:Cardiac Pacing, Artificial; D004562:Electrocardiography; D005071:Evoked Potentials / Q000502:physiology*; D006325:Heart Atria / Q000473:pathology* / Q000503:physiopathology*; D006329:Heart Conduction System / Q000473:pathology / Q000503:physiopathology; D006339:Heart Rate / Q000502:physiology*; D006801:Humans; D008297:Male; D008875:Middle Aged; D011446:Prospective Studies; D012680:Sensitivity and Specificity; D013997:Time Factors