title: Use of electroanatomic mapping to delineate transseptal atrial conduction in humans.
abstract: BACKGROUND
  Interaction between wave fronts in the right and left atrium may be important for maintenance of atrial fibrillation, but little is known about electrophysiological properties and preferential routes of transseptal conduction.
  
  
  RESULTS
  Eighteen patients (age 44+/-12 years) without structural heart disease underwent right atrial electroanatomic mapping during pacing from the distal coronary sinus (CS) or the posterior left atrium. During distal CS pacing, 9 patients demonstrated a single transseptal breakthrough near the CS os, 1 patient in the high right atrium near the presumed insertion of Bachmann's bundle and 1 patient near the fossa ovalis. The mean activation time from stimulus to CS os was 48+/-15 ms compared with 86+/-15 ms to Bachmann's bundle insertion (P<0.01) and 59+/-23 ms to the fossa ovalis (P=NS and P<0.01, respectively). During left atrial pacing, the earliest right atrial activation was near Bachmann's bundle in 5 and near the fossa ovalis in 4 patients. The activation time from stimulus to CS os was 70+/-15 ms compared with 47+/-16 ms to Bachmann's bundle (P<0.01) and 59+/-25 ms to the fossa ovalis (P=NS). Whereas the total septal activation time was not significantly different during CS pacing compared with left atrial pacing (41+/-16 versus 33+/-17 ms), the total right atrial activation time was longer during CS pacing (117+/-49 versus 79+/-15 ms; P<0.05).
  
  
  CONCLUSIONS
  Three distinct sites of early right atrial activation may be demonstrated during left atrial pacing. These sites are in accord with anatomic muscle bundles and may have relevance for maintenance of atrial flutter or fibrillation.
authors.affiliation: Section of Cardiac Electrophysiology, Department of Medicine and Cardiovascular Research Institute, University of California San Francisco, San Francisco 94143-1354, USA.
authors.forename: F X
authors.initials: FX
authors.lastname: Roithinger
authors.forename: J
authors.initials: J
authors.lastname: Cheng
authors.forename: A
authors.initials: A
authors.lastname: SippensGroenewegen
authors.forename: R J
authors.initials: RJ
authors.lastname: Lee
authors.forename: L A
authors.initials: LA
authors.lastname: Saxon
authors.forename: M M
authors.initials: MM
authors.lastname: Scheinman
authors.forename: M D
authors.initials: MD
authors.lastname: Lesh
mesh_terms: D000328:Adult; D016275:Atrial Function; D018780:Body Surface Potential Mapping / Q000379:methods*; D004553:Electric Conductivity; D004594:Electrophysiology; D005260:Female; D006329:Heart Conduction System / Q000502:physiology*; D006801:Humans