title: Prevalence and types of pitfall in the assessment of mitral isthmus linear conduction block.
abstract: BACKGROUND
  To identify and understand clinically encountered pitfalls in the assessment of transmitral conduction block using differential coronary sinus and left atrial appendage pacing techniques in patients with left mitral isthmus linear ablation.
  
  
  RESULTS
  All the available assessments of mitral isthmus block were thoroughly reviewed in 271 mitral isthmus ablation procedures undertaken among 236 patients from October 2008 to April 2011. Bidirectional block was established in 186 of 271 (69%) procedures. Careful evaluation of electrograms recorded on the multipolar coronary sinus and ablation catheters was undertaken to identify and understand the characteristics of pitfall, if any. Pitfall was encountered in 55 of 271 (20%) procedures among 51 patients and categorized into 6 types (types 1, 3, 4, and 5 led to spurious diagnosis of block; types 2 and 6 led to erroneous diagnosis of absence of block). There were 14, 10, 17, 2, 15, and 3 (total=61) cases of pitfall types 1 through 6, respectively. Operator recognized 42 of 61 (69%) pitfalls intraprocedurally. Recognition of types 1 and 5 was difficult because of indiscernible electrograms at usual amplifier settings or presence of slow conduction mimicking block.
  
  
  CONCLUSIONS
  Every fifth assessment of bidirectional block across mitral isthmus linear lesion using differential coronary sinus and left atrial appendage pacing techniques encounters a pitfall, which can lead to erroneous clinical diagnosis of block or absence of block. Recognition of pitfall during the procedure is feasible and necessitates careful distinction of far-field left atrium from the local coronary sinus electrograms besides appropriate adjustments in catheter position and pacing outputs.
authors.affiliation: Hôpital Cardiologique du Haut-Lévêque and Université Victor Segalen, Bordeaux II, Bordeaux-Pessac, France. drashahep@gmail.com
authors.forename: Ashok J
authors.initials: AJ
authors.lastname: Shah
authors.forename: Patrizio
authors.initials: P
authors.lastname: Pascale
authors.forename: Shinsuke
authors.initials: S
authors.lastname: Miyazaki
authors.forename: Xingpeng
authors.initials: X
authors.lastname: Liu
authors.forename: Laurent
authors.initials: L
authors.lastname: Roten
authors.forename: Nicolas
authors.initials: N
authors.lastname: Derval
authors.forename: Amir S
authors.initials: AS
authors.lastname: Jadidi
authors.forename: Daniel
authors.initials: D
authors.lastname: Scherr
authors.forename: Stephen B
authors.initials: SB
authors.lastname: Wilton
authors.forename: Michala
authors.initials: M
authors.lastname: Pedersen
authors.forename: Sebastien
authors.initials: S
authors.lastname: Knecht
authors.forename: Frédéric
authors.initials: F
authors.lastname: Sacher
authors.forename: Pierre
authors.initials: P
authors.lastname: Jaïs
authors.forename: Michel
authors.initials: M
authors.lastname: Haïssaguerre
authors.forename: Mélèze
authors.initials: M
authors.lastname: Hocini
mesh_terms: D020517:Atrial Appendage / Q000503:physiopathology / Q000601:surgery; D001281:Atrial Fibrillation / Q000503:physiopathology* / Q000601:surgery*; D054537:Atrioventricular Block / Q000503:physiopathology* / Q000601:surgery*; D002304:Cardiac Pacing, Artificial / Q000379:methods*; D017115:Catheter Ablation / Q000379:methods*; D016009:Chi-Square Distribution; D004562:Electrocardiography; D022062:Electrophysiologic Techniques, Cardiac; D005260:Female; D006329:Heart Conduction System / Q000503:physiopathology* / Q000601:surgery*; D006801:Humans; D008297:Male; D008943:Mitral Valve / Q000503:physiopathology* / Q000601:surgery*; D015995:Prevalence; D012189:Retrospective Studies