A previous study found that the adjunctive use of intravenous
magnesium sulfate with
ibutilide could increase the odds of a patient chemically cardioverting from
atrial fibrillation (AF) or flutter (AFL) to normal sinus rhythm (NSR) by 78%. Whether or not intravenous
magnesium has the same effect on
dofetilide's ability to chemically cardiovert patients from AF/AFL to NSR is not known.
METHODS AND RESULTS: This was a retrospective cohort evaluation of consecutive eligible patients receiving
dofetilide for chemical
cardioversion of AF or AFL at a single institution. All AF or AFL patients received
dofetilide according to the institution's standard protocol, which required patients to remain as an inpatient for a minimum of 3 days or 6 doses after the initiation of
dofetilide therapy. Patients receiving any dose of intravenous
magnesium starting on the same day as
dofetilide constituted the treatment group. Controls received
dofetilide, but no intravenous
magnesium any time prior to chemical
cardioversion. Patients underwent continuous electrocardiographic monitoring throughout their hospital admission. Multivariable logistic regression analysis was used to determine the impact of intravenous
magnesium on
dofetilide's efficacy. A total of 160 patients in persistent AF or AFL (mean age 66.6 +/- 11.0 years, 70.0% male, 30.0% in AF or AFL >15 days, 54.4%
hypertension, 37.5%
heart failure, 16.3% valvular disease, 16.3% previous
myocardial infarction, and baseline serum
magnesium levels 2.1 +/- 0.26 mg/dL) and receiving
dofetilide (mean dose 428 +/- 118 microg/dose) were included in this analysis. The overall chemical
cardioversion rate with
dofetilide irrespective of adjunctive intravenous
magnesium utilization was 41.9%. The concurrent administration of intravenous
magnesium (n = 50) was associated with a 107% increased odds of successful chemical
cardioversion [adjusted odds ratio: 2.07 (95% confidence intervals: 1.00-4.33)] compared with those who did not receive
magnesium (n = 110). Only one case of
torsade de pointes occurred in the no
magnesium group during the index hospital admission.
CONCLUSION: Concurrent use of intravenous
magnesium is associated with an enhanced ability of
dofetilide to successfully convert AF or AFL.