Study Objective.

The objective of this study is to evaluate the difference in response to ventricular rate control with intravenous (IV) metoprolol compared to IV diltiazem in patients taking chronic beta-blocker therapy who present to the emergency department (ED) in atrial fibrillation (AF) with rapid ventricular rate (RVR).

This was a single-center, retrospective study of adult patients taking chronic oral metoprolol. Chronic metoprolol therapy was defined as patients prescribed and taking oral metoprolol within 5days of study inclusion. Rate control was defined as either a decrease in ventricular rate<100bpm or <120bpm if the decrease was at least 20% from the presenting heart rate.

A total of 332 patients were included, with 16 patients in the IV diltiazem group and 316 patients in the IV metoprolol group. In the diltiazem arm, 68.8% of patients achieved successful rate control compared to 42.4% of patients in the metoprolol group (p=0.067). Treatment with IV metoprolol resulted in more hospital admissions (58% vs. 6.25% with diltiazem, p<0.001). Treatment with diltiazem was associated with a greater incidence of bradycardia compared to IV metoprolol (13% vs. 0%, p=0.002).

The use of IV diltiazem was associated with a higher rate of successful response to rate control compared to IV metoprolol in patients in AF with RVR on chronic beta-blocker therapy, however the difference between groups was not statistically significant.