title: Substrate mapping to detect abnormal atrial endocardium with slow conduction in patients with atypical right atrial flutter.
abstract: OBJECTIVE
  The purpose of this study was to investigate the relationship between the abnormal substrate and peak negative voltage (PNV) in the right atrium (RA) with atypical flutter.
  
  
  BACKGROUND
  The impact of a local abnormally low voltage electrogram on the local activation pattern and velocity of atrial flutter (AFL) remains unclear.
  
  
  METHODS
  Twelve patients with clinically documented AFL were included to undergo noncontact mapping of the RA. The atrial substrate was characterized by the: 1) activation mapping; 2) high-density voltage mapping; and 3) conduction velocity along the flutter re-entrant circuit. The normalized PNV (i.e., the relative ratio to the maximal PNV) in each virtual electrode recording was used to produce the voltage maps of the entire chamber. The protected isthmus was bordered by low voltage zones.
  
  
  RESULTS
  Atypical AFL of the RA was induced by atrial pacing in 12 patients, including 10 upper loop re-entry and 2 RA free wall re-entry flutter. These protected isthmuses were located near the crista terminalis. The mean width of the protected isthmus was 1.7 +/- 0.3 cm and mean voltage at the isthmus was -0.91 +/- 0.39 mV. The conduction velocities within these paths were significantly slower than outside the path (0.30 +/- 0.18 m/s vs. 1.14 +/- 0.41 m/s, respectively; p = 0.004). The ratiometric PNV of 37.6% of the maximal PNV had the best cut-off value to predict slow conduction, with a high sensitivity (92.3%) and specificity (85.7%).
  
  
  CONCLUSIONS
  Characterization of the RA substrate in terms of the unipolar PNV is an effective predictor of the slow conduction path within the critical isthmus of the re-entrant circuit.
authors.affiliation: Institute of Clinical Medicine and Cardiovascular Research Institute, National Yang-Ming University, Taipei, Taiwan.
authors.forename: Jin Long
authors.initials: JL
authors.lastname: Huang
authors.forename: Ching-Tai
authors.initials: CT
authors.lastname: Tai
authors.forename: Yenn-Jiang
authors.initials: YJ
authors.lastname: Lin
authors.forename: Bien-Hsien
authors.initials: BH
authors.lastname: Huang
authors.forename: Kun-Tai
authors.initials: KT
authors.lastname: Lee
authors.forename: Satoshi
authors.initials: S
authors.lastname: Higa
authors.forename: Yoga
authors.initials: Y
authors.lastname: Yuniadi
authors.forename: Yi-Jen
authors.initials: YJ
authors.lastname: Chen
authors.forename: Shih-Lin
authors.initials: SL
authors.lastname: Chang
authors.forename: Li-Wei
authors.initials: LW
authors.lastname: Lo
authors.forename: Wanwarang
authors.initials: W
authors.lastname: Wongcharoen
authors.forename: Chih-Tai
authors.initials: CT
authors.lastname: Ting
authors.forename: Shih-Ann
authors.initials: SA
authors.lastname: Chen
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D001282:Atrial Flutter / Q000175:diagnosis* / Q000503:physiopathology* / Q000601:surgery; D016280:Atrial Function, Right; D017115:Catheter Ablation; D022062:Electrophysiologic Techniques, Cardiac; D004699:Endocardium / Q000503:physiopathology*; D005260:Female; D006329:Heart Conduction System / Q000503:physiopathology*; D006801:Humans; D008297:Male; D008875:Middle Aged; D013997:Time Factors; D016896:Treatment Outcome