title: Acute beta-adrenoceptor blockade improves efficacy of ibutilide in conversion of atrial fibrillation with a rapid ventricular rate.
abstract: OBJECTIVE
  Activation of beta-adrenoceptors attenuates prolongation of action potential duration induced by blockade of the delayed rectifier potassium current. We examined whether acute administration of beta-blocker could enhance ibutilide (IB) efficacy in conversion of atrial fibrillation (AF) with a rapid ventricular rate.
  
  
  RESULTS
  Ninety patients (aged 63 +/- 13.5 years) with rapidly conducting AF were randomized in to two groups. Group A (n = 44) received esmolol titrated to achieve a heart rate of <100 bpm followed by IB co-administration, while Group B (n = 46) were treated with IB as monotherapy. In Group A, 29 patients (67%) converted to sinus rhythm (SR) compared with 21 (46%) in Group B (P = 0.04). The use of esmolol was the most important predictor for cardioversion (P = 0.009). The slower the heart rate at the time of IB initiation, the higher the likelihood for cardioversion (P = 0.015). Patients in Group A had significantly shorter corrected QT interval (QTc) at the time of conversion than those in Group B (433 vs. 501 ms, P = 0.003). Two patients in Group A developed severe bradycardia, whereas three patients in Group B developed severe ventricular tachycardia (VT).
  
  
  CONCLUSIONS
  Compared with IB monotherapy, the combination therapy of esmolol and IB appears to be more effective in conversion of rapidly conducting AF back to SR. The addition of beta-blocker reduces QTc prolongation and diminishes the risk of VT at the expense, however, of increased bradycardic events.
authors.affiliation: 2nd Cardiology Department, General Hospital G. Papanikolaou, Exochi, Thessaloniki, Greece. nfrag@vodafone.net.gr
authors.forename: Nikolaos
authors.initials: N
authors.lastname: Fragakis
authors.forename: Athanasios
authors.initials: A
authors.lastname: Bikias
authors.forename: Ioannis
authors.initials: I
authors.lastname: Delithanasis
authors.forename: Melania
authors.initials: M
authors.lastname: Konstantinidou
authors.forename: Nikolaos
authors.initials: N
authors.lastname: Liakopoulos
authors.forename: Miltiadis
authors.initials: M
authors.lastname: Kozirakis
authors.forename: George
authors.initials: G
authors.lastname: Katsaris
mesh_terms: D000319:Adrenergic beta-Antagonists / Q000008:administration & dosage*; D000889:Anti-Arrhythmia Agents / Q000008:administration & dosage / Q000009:adverse effects; D001281:Atrial Fibrillation / Q000150:complications* / Q000517:prevention & control*; D004357:Drug Synergism; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D011412:Propanolamines / Q000008:administration & dosage*; D013449:Sulfonamides / Q000008:administration & dosage* / Q000009:adverse effects; D016896:Treatment Outcome; D014693:Ventricular Fibrillation / Q000139:chemically induced / Q000517:prevention & control*
chemical_list: D000319:Adrenergic beta-Antagonists; D000889:Anti-Arrhythmia Agents; D011412:Propanolamines; D013449:Sulfonamides; C067192:ibutilide; C036604:esmolol