AbstractBackgroundMagnesium is believed to have a physiologic role in cardiac contractility, and evidence from epidemiologic and clinical studies has suggested that low serum concentrations of magnesium may be associated with increased risk of atrial fibrillation (AF).ObjectiveAs part of the planning effort for a large randomized trial to prevent AF with magnesium supplementation, we conducted a 12-week pilot study to assess adherence to oral magnesium supplementation and matching placebo, estimate the effect on circulating magnesium concentrations, and evaluate the feasibility of using an ambulatory monitoring device (ZioPatch) for assessing premature atrial contractions (PACs), a predictor of AF.DesignDouble-blind randomized pilot clinical trial comparing supplementation with 400 mg magnesium oxide daily (versus placebo) over 12 weeks of follow-up. The ZioPatch was applied for 14 days at baseline and the end of follow-up. Adherence to the assigned treatment, and changes in PACs, serum magnesium concentration, glucose and blood pressure were assessed.ResultsA total of 59 participants, 73% women and average age 62 years, were randomized. 98% of participants completed follow-up. Those assigned to the magnesium supplement took 75% of tablets as compared to 83% for those in the placebo group. Change in magnesium concentrations was significantly greater for those given magnesium supplement compared to placebo (0.07; 95% confidence interval (CI): 0.03, 0.12 mEq/L; p = 0.002). ZioPatch was worn for an average of 13.0 of the requested 14 days at baseline; at the end of follow-up, the average number of days of monitoring was 13.0 days for the magnesium supplement group and 12.7 days for the placebo group. For log PAC burden (episodes per hour), the average change from baseline was −0.05 (95% CI: −0.31, 0.20) for those randomized to magnesium supplement and 0.04 (95% CI: −0.24, 0.31) for those randomized to placebo (p=0.79 for difference). Gastrointestinal problems were reported by 50% of participants in the magnesium supplement group and 7% in the placebo group. Only one person in the magnesium supplement group and none in the placebo group experienced adverse events which led to treatment discontinuation.ConclusionsIn this pilot randomized clinic trial, although gastrointestinal side effects to the magnesium supplement were common, adherence, measured by pill counts, was very good and, as a consequence, magnesium concentrations were greater for those randomly assigned to the magnesium supplement compared to placebo. Participant acceptance of the planned monitoring with ZioPatch was also very good. While the difference in the change in PACs was not significant, this pilot study was small, short-term, and did not include participants at high risk of AF. Thus, we could not reliably evaluate the effect of magnesium supplementation on PACs.Clinicaltrials.gov registrationNCT02837328
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