Pre-injection of magnesium sulfate enhances the efficacy of ibutilide for the conversion of typical but not of atypical persistent atrial flutter.
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.
Steinwender
Clemens
C
Cardiovascular Division, Academic Teaching and General Hospital Linz, Linz, Austria. clemens.steinwender@akh.linz.at
Hönig
Simon
S
Kypta
Alexander
A
Kammler
Jürgen
J
Schmitt
Barbara
B
Leisch
Franz
F
Hofmann
Robert
R
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
D000889:Anti-Arrhythmia Agents; D013449:Sulfonamides; C067192:ibutilide; D008278:Magnesium Sulfate