title: Pre-injection of magnesium sulfate enhances the efficacy of ibutilide for the conversion of typical but not of atypical persistent atrial flutter.
abstract: BACKGROUND
  Ibutilide is a class III antiarrhythmic drug, frequently used for conversion of atrial fibrillation and flutter. Retrospective cohort evaluations found that intravenous application of magnesium enhances the efficacy of ibutilide for chemical conversion of these arrhythmias. This prospective study sought to investigate the effects of intravenously pre-injected magnesium on the conversion rate of ibutilide for typical and atypical atrial flutter.
  
  
  METHODS
  We performed a prospective, randomized, placebo-controlled study. Patients with typical atrial flutter (TAF) or atypical atrial flutter (AAF) were randomized to receive either 4 g of intravenous magnesium sulfate or placebo immediately before administration of a maximum dose of 2 mg of ibutilide fumarate. Continuous rhythm monitoring for 4 h provided information on conversion to sinus rhythm. QT interval durations were measured before randomization, after magnesium, as well as 30 min and 4 h after starting ibutilide infusion.
  
  
  RESULTS
  We randomized 117 patients (58 with and 59 without pre-injection of magnesium; 65 with TAF and 52 with AAF). In patients with TAF, pre-injection of magnesium significantly improved the efficacy of ibutilide for conversion (85% with magnesium vs. 59% with placebo, p=0.017). In patients with AAF, no significant difference in conversion rates between patients receiving magnesium or placebo was detected (48% vs. 56%, p=0.189). Pre-injection of magnesium did not significantly influence the QT intervals at any time after administration of ibutilide.
  
  
  CONCLUSIONS
  Pre-injection of magnesium significantly enhances the efficacy of ibutilide for the conversion of TAF but not of AAF.
authors.affiliation: Cardiovascular Division, Academic Teaching and General Hospital Linz, Linz, Austria. clemens.steinwender@akh.linz.at
authors.forename: Clemens
authors.initials: C
authors.lastname: Steinwender
authors.forename: Simon
authors.initials: S
authors.lastname: Hönig
authors.forename: Alexander
authors.initials: A
authors.lastname: Kypta
authors.forename: Jürgen
authors.initials: J
authors.lastname: Kammler
authors.forename: Barbara
authors.initials: B
authors.lastname: Schmitt
authors.forename: Franz
authors.initials: F
authors.lastname: Leisch
authors.forename: Robert
authors.initials: R
authors.lastname: Hofmann
mesh_terms: D000368:Aged; D000889:Anti-Arrhythmia Agents / Q000008:administration & dosage*; D001281:Atrial Fibrillation / Q000188:drug therapy / Q000503:physiopathology; D001282:Atrial Flutter / Q000188:drug therapy* / Q000503:physiopathology; D004357:Drug Synergism; D004562:Electrocardiography / Q000187:drug effects; D005260:Female; D006329:Heart Conduction System / Q000187:drug effects*; D006801:Humans; D007275:Injections, Intravenous; D008278:Magnesium Sulfate / Q000008:administration & dosage*; D008297:Male; D008875:Middle Aged; D015990:Placebo Effect; D011446:Prospective Studies; D013449:Sulfonamides / Q000008:administration & dosage*; D016896:Treatment Outcome
chemical_list: D000889:Anti-Arrhythmia Agents; D013449:Sulfonamides; C067192:ibutilide; D008278:Magnesium Sulfate