DOsing Strategy Effectiveness of Diltiazem in Atrial Fibrillation With Rapid Ventricular Response.

Study Objective: To evaluate the dose-dependent comparative safety and effectiveness between weight-based and alternative dosing strategies for diltiazem in atrial fibrillation with rapid ventricular response.

Methods: This retrospective cohort study included adult patients presenting to the emergency department (ED) with atrial fibrillation with rapid ventricular response who received treatment with intravenous diltiazem. Groups were retrospectively categorized according to the initial dose: low (<0.1875 mg/kg), weight-based (0.1875 to 0.3125 mg/kg), and high (>0.3125 mg/kg). The primary outcome was rate control (heart rate <100 beats/min) within 30 minutes of treatment.

Results: Of 345 records, 252 were included. Because of scarcity (N=6), outcomes for the high-dose group were not analyzed. By 30 minutes, the weight-based dosing group had more often achieved rate control (weight-based 55%; low 27%; difference 29% [95% confidence interval (CI) 17% to 40%]). Regression analysis identified the weight-based dosing group (odds ratio 3.63, 95% CI 2.06 to 6.39) and initial heart rate of less than 145 beats/min (odds ratio 2.56, 95% CI 1.46 to 4.51) as variables associated with the primary outcome. The weight-based dosing group less often required rescue therapy (weight-based 6%; low 17%; difference -12% [95% CI -20% to -4%]) relative to the low-dose group. Mortality was higher in the low-dose group than in the weight-based dosing group (low 7%; weight-based 1%; difference 6% [95% CI 1% to 11%]).

Conclusion: This study shows dose-dependent hemodynamic effects with diltiazem in patients with atrial fibrillation with rapid ventricular response. Weight-based diltiazem (0.25 mg/kg) was associated with greater rate control with no evidence of increased adverse effects. There was no perceived advantage in using lower, alternative doses.