title: Blanked atrial flutter in patients with cardiac resynchronization therapy: clinical significance and implications for device programming.
abstract: BACKGROUND
  Atrial arrhythmias are frequently observed in patients with heart failure and may be a primary cause for decompensation during cardiac resynchronization therapy (CRT). The accurate detection of organized atrial tachyarrhythmias poses a challenge to the function of mode-switching biventricular pacemakers/defibrillators.
  
  
  METHODS
  The purpose of the study was to determine retrospectively the incidence of blanked atrial flutter and mode switch failure (2:1 lock-in), and to look for factors predisposing to this problem. A total number of 65 patients with CRT devices has been followed regularly over 18 +/- 12 months. Five patients were excluded because of chronic atrial fibrillation and reprogramming to VVIR mode.
  
  
  RESULTS
  Seven out of 60 patients (12%) were diagnosed with blanked atrial flutter at unscheduled device interrogation. Sustained biventricular pacing at a median rate of 125/min-mimicking sinus tachycardia-resulted in rapid deterioration of heart failure and hospitalization. Mode switch failure occurred due to coincidence of every second flutter wave with atrial blanking. The group with 2:1 lock-in was programmed to longer atrial blanking times (143 +/- 34 ms vs 105 +/- 32 ms; P = 0.026) and AV intervals (126 +/- 8 ms vs 107 +/- 29; P = 0.001) than the group without lock-in. Other clinical characteristics examined did not differ between the two groups apart from a previous history of atrial fibrillation (P = 0.032).
  
  
  CONCLUSIONS
  Blanked atrial flutter with rapid ventricular pacing is a clinically important problem in heart failure patients treated with CRT devices. Efforts should be made to avoid this complication by atrial lead implantation without ventricular farfield oversensing, by programming short PVAB and AV intervals, and by implementation of dedicated device algorithms.
authors.affiliation: Department of Cardiology, Salzburger Landeskliniken, Paracelsus Private Medical University, Salzburg, Austria. B.Strohmer@salk.at
authors.forename: Bernhard
authors.initials: B
authors.lastname: Strohmer
authors.forename: Christiana
authors.initials: C
authors.lastname: Schernthaner
authors.forename: Maximilian
authors.initials: M
authors.lastname: Pichler
mesh_terms: D000368:Aged; D001282:Atrial Flutter / Q000453:epidemiology* / Q000517:prevention & control*; D015984:Causality; D015897:Comorbidity; D004554:Electric Countershock / Q000706:statistics & numerical data*; D005260:Female; D006333:Heart Failure / Q000453:epidemiology* / Q000517:prevention & control*; D006801:Humans; D015994:Incidence; D008297:Male; D008875:Middle Aged; D011379:Prognosis; D012189:Retrospective Studies; D018570:Risk Assessment / Q000379:methods*; D016896:Treatment Outcome