title: Prospective observations in the clinical and electrophysiological characteristics of intra-isthmus reentry.
abstract: BACKGROUND
  Intra-isthmus reentry (IIR) is a circuit within the cavotricuspid isthmus (CTI). The purpose of this study is to prospectively define the electrogram and surface ECG characteristics of IIR, and its clinical implications.
  
  
  RESULTS
  Fourteen patients underwent electrophysiological studies and were found to have IIR. Detailed electrogram mapping of the CTI was available in all, electroanatomic mapping (EAM) in 8 of 14 (57%) patients. In all, entrainment mapping during tachycardia proved reentry, and showed that the anteroinferior CTI was out of the circuit and the septal CTI was in the circuit in 12 of 14 patients, whereas in 2, the circuit was confined within the mid and/or anteroinferior CTI. Fractionated potentials (FPs) spanning 34-71% of the tachycardia cycle length were recorded within the CTI in all, and double potentials were inscribed in 10 of 14 (71%). Analysis of the tricuspid annulus electrograms showed spontaneous shifts from a counterclockwise (CCW) to clockwise or fusion patterns. Surface ECGs showed either typical CCW pattern (12 patients) or atypical patterns (3 patients). The EAMs showed a focal pattern in 3, a CCW pattern in 5. The successful ablation site always occurred at the area with maximal FP duration. Over the same period, 33 of 384 (9%) patients who underwent ablation for CTI-dependent flutter had prior successful CTI ablation, 7 of 33 (21%) were found to have IIR during the redo procedure.
  
  
  CONCLUSIONS
  (1) Electrogram and ECG patterns of IIR frequently show atypical flutter. (2) IIR was successfully ablated in an area of the CTI associated with maximal duration of FPs. (3) IIR is a significant cause of "recurrent flutter" in patients with prior CTI ablation.
authors.affiliation: University of California-San Francisco, San Francisco, California 94143-1354, USA.
authors.forename: Yanfei
authors.initials: Y
authors.lastname: Yang
authors.forename: Niraj
authors.initials: N
authors.lastname: Varma
authors.forename: Nitish
authors.initials: N
authors.lastname: Badhwar
authors.forename: Ronn E
authors.initials: RE
authors.lastname: Tanel
authors.forename: Sirisha
authors.initials: S
authors.lastname: Sundara
authors.forename: Randall J
authors.initials: RJ
authors.lastname: Lee
authors.forename: Byron K
authors.initials: BK
authors.lastname: Lee
authors.forename: Zian H
authors.initials: ZH
authors.lastname: Tseng
authors.forename: Gregory M
authors.initials: GM
authors.lastname: Marcus
authors.forename: Albert M
authors.initials: AM
authors.lastname: Kim
authors.forename: Jeffrey E
authors.initials: JE
authors.lastname: Olgin
authors.forename: Melvin M
authors.initials: MM
authors.lastname: Scheinman
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D001282:Atrial Flutter / Q000145:classification* / Q000175:diagnosis*; D018780:Body Surface Potential Mapping / Q000379:methods*; D004569:Electroencephalography / Q000379:methods*; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D011446:Prospective Studies; D055815:Young Adult