title: Atrial flutter ablation: correlation between isthmic activation times and flutter cycle.
abstract: BACKGROUND
  Ablation of typical atrial flutter relies on the suppression of electrical conduction along the cavo-tricuspid isthmus. Bidirectional isthmus block is a criterion of successful ablation and is associated with the presence of different activation times on each side of the ablation line.
  
  
  OBJECTIVE
  The aim of this study was to determine whether the difference in isthmic activation times correlates with the length of the atrial flutter cycle.
  
  
  METHODS
  We studied 31 patients with typical atrial flutter (93.6% male, mean age 66 +/- 9 years) who underwent successful ablation during tachycardia. CARTO electroanatomic mapping was used to confirm diagnosis of isthmus-dependent atrial flutter, guide the ablation line creation and assess its efficacy. At the end of the procedure, a three-dimensional activation map of the right atrium was constructed, under pacing from the coronary sinus ostium (with a 500 ms cycle). Activation times on the lateral (right) and septal (left) sides of the ablation line were measured. The difference between these two activation times was termed the difference in isthmic activation times (delta IAT), and was compared to the flutter cycle length.
  
  
  RESULTS
  Mean activation times were 173.7 +/- 34.3 ms on the lateral border of the ablation line and 19.1 +/- 12.5 ms on the septal border. Mean delta IAT was 154.6 +/- 27.8 ms and mean atrial flutter cycle length was 257.5 +/- 30.6 ms. delta IAT and flutter cycle length were significantly correlated (r = 0.503, p = 0.0039). The linear regression equation that best described this result was: delta IAT = 37 + (0.46 x flutter cycle).
  
  
  CONCLUSIONS
  After atrial flutter ablation, a difference in isthmic activation times of more than half the flutter cycle length was associated with isthmus conduction block.
authors.affiliation: Serviço de Cardiologia, Hospital de Santa Cruz, Carnaxide, Portugal. katyars@netcabo.pt
authors.forename: Katya
authors.initials: K
authors.lastname: Reis-Santos
authors.forename: Pedro
authors.initials: P
authors.lastname: Adragão
authors.forename: Carlos
authors.initials: C
authors.lastname: Aguiar
authors.forename: Diogo
authors.initials: D
authors.lastname: Cavaco
authors.forename: Francisco
authors.initials: F
authors.lastname: Morgado
authors.forename: Luís
authors.initials: L
authors.lastname: Raposo
authors.forename: Dipali
authors.initials: D
authors.lastname: Chotalal
authors.forename: Daniel
authors.initials: D
authors.lastname: Bonhorst
authors.forename: Ricardo
authors.initials: R
authors.lastname: Seabra-Gomes
mesh_terms: D000368:Aged; D001282:Atrial Flutter / Q000503:physiopathology* / Q000601:surgery*; D005260:Female; D006801:Humans; D008297:Male; D012189:Retrospective Studies; D013997:Time Factors