Background: Intravenous (IV) diltiazem is indicated for acute atrial fibrillation or flutter (AFF) but real-world dosing strategies often differ from labeling. Objective: To characterize “on-label” use of IV diltiazem in acute AFF. Methods: An IRB-approved, single-center, retrospective, observational design was utilized. Eligible patients had acute AFF with heart rate > 120 bpm and received IV diltiazem between June 2012 – June 2014. The primary outcome was frequency of on-label use of IV diltiazem, defined as use of at least one FDA-approved weight-based bolus dose followed by an infusion, if appropriate, in the absence of contraindications. Results: 300 patients were screened; 97 patients were included for analysis. IV diltiazem was used on-label in only 14 patients (14.4%). Of the 96 patients who received an initial diltiazem bolus, the median dose was significantly higher in patients for whom the diltiazem dose was on-label [17.5 mg (IQR 10-20 mg) vs. 10.0 mg (IQR 10-20 mg), p < 0.02). Twenty-nine patients (34.9%) in the off-label group had a therapeutic response to diltiazem alone compared to 8 patients (57.1%) in the on-label group (p = 0.11). More patients treated with off label diltiazem boluses required additional rate control medications (40.9% vs. 7.1%, p < 0.04). Conclusion: IV diltiazem was not used in accordance with FDA labeling in the majority of patients. For most patients, IV diltiazem doses were lower than recommended and many of these patients required additional rate control medications to achieve a therapeutic response. Patients with tachycardia due to acute AFF may benefit from improved IV diltiazem dosing strategies or the use of alternative rate-control agents (e.g. beta blockers)
