Aims: 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.