title: Rate-dependent and site-specific conduction block at the posterior right atrium and drug effects evaluated using a noncontact mapping system in patients with typical atrial flutter.
abstract: BACKGROUND
  Conduction block in the posterior right atrium (RA) plays an important role in perpetuating atrial flutter (AFL). Although conduction blocks have functional properties, it is not clear how the block line changes with the pacing rate, pacing site, and administration of antiarrhythmic drugs.
  
  
  RESULTS
  Forty patients with typical AFL were enrolled. Pacing (110, 170, 230 ppm) from the coronary sinus ostium (CSo) and low lateral RA was performed. After 1 mg/kg pilsicainide (pure sodium channel blockade) administration, the pacing protocol was repeated. Conduction block was assessed based on a color-coded isopotential map and 20 points of virtual unipolar electrograms in the posterior RA using noncontact mapping. Block line proportion was defined as the percentage of length of the block line between the superior and inferior vena cava. The pacing rate-dependent extension of the block proportion was significant during pacing from both sides (pacing from the CSo: 59 ± 17% at 110 ppm, 69 ± 16% at 230 ppm, P < 0.05; pacing from the low lateral RA: 43 ± 19% at 110 ppm, 55 ± 22% at 230 ppm, P < 0.05). The block line was significantly longer during CSo pacing than during low lateral RA pacing at each rate (all P < 0.05). After pilsicainide administration, the block line extended further.
  
  
  CONCLUSIONS
  In addition to pacing rate-dependent and site-dependent changes in the block line, pilsicainide further extended the block line length. This phenomenon explains the clinical observation that counterclockwise AFL occurs more frequently than clockwise AFL, and the mechanism of class IC AFL.
authors.affiliation: Section of Arrhythmia, Division of Cardiovascular Medicine, Department of Internal Medicine, Kobe University Graduate School of Medicine, Hyogo, Japan.
authors.forename: Mitsuru
authors.initials: M
authors.lastname: Takami
authors.forename: Akihiro
authors.initials: A
authors.lastname: Yoshida
authors.forename: Koji
authors.initials: K
authors.lastname: Fukuzawa
authors.forename: Asumi
authors.initials: A
authors.lastname: Takei
authors.forename: Gaku
authors.initials: G
authors.lastname: Kanda
authors.forename: Kaoru
authors.initials: K
authors.lastname: Takami
authors.forename: Hiroyuki
authors.initials: H
authors.lastname: Kumagai
authors.forename: Satoko
authors.initials: S
authors.lastname: Tanaka
authors.forename: Mitsuaki
authors.initials: M
authors.lastname: Itoh
authors.forename: Kimitake
authors.initials: K
authors.lastname: Imamura
authors.forename: Ryudo
authors.initials: R
authors.lastname: Fujiwara
authors.forename: Atsushi
authors.initials: A
authors.lastname: Suzuki
authors.forename: Ken-Ichi
authors.initials: K
authors.lastname: Hirata
mesh_terms: D000200:Action Potentials; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000889:Anti-Arrhythmia Agents / Q000627:therapeutic use*; D001282:Atrial Flutter / Q000175:diagnosis / Q000188:drug therapy / Q000503:physiopathology; D002304:Cardiac Pacing, Artificial; D017115:Catheter Ablation; D022062:Electrophysiologic Techniques, Cardiac; D005260:Female; D006325:Heart Atria / Q000187:drug effects / Q000503:physiopathology; D006327:Heart Block / Q000175:diagnosis / Q000188:drug therapy / Q000503:physiopathology; D006329:Heart Conduction System / Q000187:drug effects / Q000503:physiopathology; D006801:Humans; D008012:Lidocaine / Q000031:analogs & derivatives* / Q000627:therapeutic use; D008297:Male; D008875:Middle Aged; D011237:Predictive Value of Tests; D026941:Sodium Channel Blockers / Q000627:therapeutic use*; D013997:Time Factors; D056969:Voltage-Sensitive Dye Imaging
chemical_list: D000889:Anti-Arrhythmia Agents; D026941:Sodium Channel Blockers; D008012:Lidocaine; C042288:pilsicainide