title: Role of right atrial endocardial structures as barriers to conduction during human type I atrial flutter. Activation and entrainment mapping guided by intracardiac echocardiography.
abstract: BACKGROUND
  The importance of barriers in atrial flutter has been demonstrated in animals. We used activation and entrainment mapping, guided by intracardiac echocardiography (ICE), to determine whether the crista terminalis (CT) and eustachian ridge (ER) are barriers to conduction during typical atrial flutter in humans.
  
  
  RESULTS
  In eight patients, ICE was used to guide the placement of 20-pole and octapolar catheters along the CT and interatrial septum and a roving catheter to nine sites: just posterior (1) and anterior (2) to the CT along the lateral right atrium, at the fossa ovalis (3), and just posterior and anterior to the ER at the low posterolateral (4 and 5), low posterior (6 and 7), and low posteromedial (8 and 9) right atrium. Entrainment was performed, and each site was considered within the flutter circuit if the postpacing interval-flutter cycle length (PPI-FCL) and the stimulus time-activation time (stim time-act time) were < 10 msec. Split potentials were recorded along the CT with components activated in a low-to-high pattern and a high-to-low pattern. Conduction times, as percentage of FCL, were significantly different at sites on either side of the CT and ER: site 1 (33 +/- 13%) and site 2 (43 +/- 12%) (P = .02), site 4 (48 +/- 24%) and site 5 (75 +/- 8.9%) (P = .02), and site 6 (22 +/- 10%) and site 7 (82 +/- 5.3%) (P = .0009). During entrainment, no surface fusion was observed at sites 5, 7, or 9. The PPI-FCL and stim time-act time were not significantly different than 0 at sites 2, 7, 5, or 9, indicating that they were within the flutter circuit, whereas sites 1, 3, 4, and 6 were not.
  
  
  CONCLUSIONS
  ICE enabled the correlation of functional electrophysiological properties with specific anatomic landmarks, identifying the CT and ER as barriers to conduction during human atrial flutter.
authors.affiliation: Department of Medicine, University of California San Francisco 94143-1354, USA.
authors.forename: J E
authors.initials: JE
authors.lastname: Olgin
authors.forename: J M
authors.initials: JM
authors.lastname: Kalman
authors.forename: A P
authors.initials: AP
authors.lastname: Fitzpatrick
authors.forename: M D
authors.initials: MD
authors.lastname: Lesh
mesh_terms: D000368:Aged; D001282:Atrial Flutter / Q000000981:diagnostic imaging / Q000503:physiopathology* / Q000601:surgery; D016280:Atrial Function, Right / Q000502:physiology; D006328:Cardiac Catheterization; D002304:Cardiac Pacing, Artificial; D017115:Catheter Ablation; D004452:Echocardiography / Q000379:methods*; D004562:Electrocardiography; D004699:Endocardium / Q000033:anatomy & histology; D005260:Female; D006325:Heart Atria / Q000033:anatomy & histology; D006329:Heart Conduction System / Q000503:physiopathology* / Q000601:surgery; D006801:Humans; D008297:Male