title: Ventricular proarrhythmic effects of atrial fibrillation are modulated by depolarization and repolarization anomalies in patients with left ventricular dysfunction.
abstract: BACKGROUND
  Atrial fibrillation (AF) may have a ventricular proarrhythmic effect, particularly in the setting of heart failure. We assessed whether AF predicts appropriate implantable cardioverter-defibrillator (ICD) shocks in patients with left ventricular dysfunction and explored modulators of risk.
  
  
  RESULTS
  A retrospective cohort study was conducted on 215 consecutive patients with ICDs for primary prevention having a left ventricular ejection fraction < or = 35%. Mean age at ICD implantation was 61.0 +/- 9.7 years and 17% were women. Overall, 22 patients (10.2%) experienced appropriate ICD shocks over a follow-up of 1.3 +/- 0.7 years, corresponding to an actuarial event-rate of 5.8% per year. In univariate analysis, AF was associated with a 3.6-fold increased risk of appropriate shocks (P = 0.0037). Annual rates of appropriate ICD shocks in patients with and without AF were 12.9% and 3.5%, respectively (P = 0.0200). In multivariate stepwise Cox regression analyses controlling for baseline imbalances, demographic parameters, underlying heart disease, and therapy, history of AF independently predicted appropriate shocks (hazard ratio 2.7, P = 0.0278). Prolonged QRS duration (>130 ms) and QTc (>440 ms) modulated the effect of AF on appropriate shocks. Patients with both AF and QRS > 130 ms were more than five times more likely to receive an appropriate ICD shock (hazard ratio 5.4, P = 0.0396). Patients with AF and QTc > 440 ms experienced a greater than 12-fold increased risk of appropriate shocks (hazard ratio 12.7, P = 0.0177).
  
  
  CONCLUSIONS
  In prophylactic ICD recipients with left ventricular dysfunction, AF is associated with increased risk for ventricular tachyarrhythmias, particularly when combined with conduction and/or repolarization abnormalities.
authors.affiliation: Electrophysiology Service, Montreal Heart Institute, University of Montreal, Montreal, Canada.
authors.forename: Kristina
authors.initials: K
authors.lastname: Lemola
authors.forename: Razi
authors.initials: R
authors.lastname: Khan
authors.forename: Stanley
authors.initials: S
authors.lastname: Nattel
authors.forename: Mario
authors.initials: M
authors.lastname: Talajic
authors.forename: Denis
authors.initials: D
authors.lastname: Roy
authors.forename: Peter G
authors.initials: PG
authors.lastname: Guerra
authors.forename: Sakari
authors.initials: S
authors.lastname: Lemola
authors.forename: Marc
authors.initials: M
authors.lastname: Dubuc
authors.forename: Bernard
authors.initials: B
authors.lastname: Thibault
authors.forename: Laurent
authors.initials: L
authors.lastname: Macle
authors.forename: Paul
authors.initials: P
authors.lastname: Khairy
mesh_terms: D001281:Atrial Fibrillation / Q000453:epidemiology* / Q000517:prevention & control*; D015331:Cohort Studies; D015897:Comorbidity; D017147:Defibrillators, Implantable; D005260:Female; D006801:Humans; D015994:Incidence; D008297:Male; D008875:Middle Aged; D011792:Quebec / Q000453:epidemiology; D012189:Retrospective Studies; D018570:Risk Assessment / Q000379:methods*; D012307:Risk Factors; D016896:Treatment Outcome; D018487:Ventricular Dysfunction, Left / Q000453:epidemiology* / Q000517:prevention & control*; D014693:Ventricular Fibrillation / Q000175:diagnosis / Q000453:epidemiology*