Currently, it remains unclear whether β-blockers or nondihydropyridine calcium channel blockers are preferred for the acute management of atrial fibrillation (AF).
The objective of this study was to compare the efficacy and safety of intravenous (IV) metoprolol and diltiazem for rate control.
This was a single-center, retrospective cohort study of patients who presented to the emergency department between 2015 and 2019 with AF with rapid ventricular rate (RVR) and received IV metoprolol or diltiazem. The primary outcome was the percentage of patients who achieved rate control (defined as heart rate < 100 beats per minute). Secondary outcomes included time to rate control, percentage of patients requiring additional agents for rate control, and incidence of cardioversion, bradycardia, and hypotension.
A total of 200 patients were included in this study. Rate control was achieved in 35% and 41% of the metoprolol and diltiazem groups, respectively ( = 0.38). Mean time to rate control was not significantly different between the metoprolol and diltiazem groups (35 vs 21 minutes,  = 0.23). One patient developed hypotension, no patient developed bradycardia, and 4 patients required electric cardioversion. No adverse events were observed in patients with ejection fraction ≤40%.
There was no difference in the achievement of rate control between IV metoprolol and diltiazem. This is the largest study to date comparing the two classes of agents for acute rate control in AF. No patient-specific factors were identified that would influence the preferential use of one medication over the other.