116: Atrium: Atrial Tachycardia Reduction With Intravenous Use of Magnesium

Introduction: Magnesium sulfate (Mg) is a safe and effective option for the management of atrial fibrillation with rapid ventricular response (AF RVR); however, the optimal dose is unknown. There is significant heterogeneity in the studied doses, ranging from 1 g to 9 g, with higher doses associated with increased adverse effects such as flushing and hypotension. The objective of this study is to compare the efficacy of lower doses of intravenous (IV) Mg to successfully decrease the ventricular rate to under 120 beats per minute (bpm) in the management of AFF RVR for patients receiving IV diltiazem. Methods: This is a prospective, double-blind, randomized controlled trial comparing Mg sulfate 2 g vs 4 g vs placebo for patients presenting with AF RVR. All study patients receive standard weight-based IV diltiazem after Mg administration is complete. The primary endpoint is rate control within the first 2 hours of IV Mg administration, defined as a ventricular rate less than 120 bpm. Secondary endpoints include the mean change in heart rate (HR) at pre-specified time points after the administration of Mg and diltiazem and mean change in HR up to 24-hours after Mg infusion. Descriptive statistics, t test, chi-squared, and ANOVA tests were used for data analysis. All tests were two-tailed and p values of 0.05 were considered statistically significant. A power analysis indicated the need for 153 subjects, 51 in each group, to detect a difference of 40 bpm. Results: A total of 30 patients (n=6, n=10, and n=14 in the placebo, Mg 2 g, and Mg 4 g arms, respectively) were enrolled as of March 30, 2025. The percentage of patients who achieved rate control within 2 hours were 50% vs 60% vs 78.5% in the placebo, Mg 2 g, and Mg 4 g arms respectively (p=0.39). The mean reduction in HR at 2 hours after Mg infusion was 25 bpm, 38 bpm, and 49 bpm in the placebo, Mg 2 g, Mg 4 g arms, respectively (p=0.07). There were no documented incidences of hypotension or bradycardia observed. Conclusions: Although not statistically significant, preliminary results indicate an improvement in rate control with Mg compared to placebo for AF RVR. These findings need to be validated with the full sample size, which is anticipated to provide sufficient power to detect a significant difference.