(916) Weight-Based Versus Fixed Diltiazem in Obesity for Atrial Fibrillation With Rapid Ventricular Rate

Introduction: Patients with obesity are not well represented in clinical studies leading to a lack of dosing information for many medications, including those used to treat atrial fibrillation with rapid ventricular rate (AF RVR). Overall, there are mixed data regarding whether weight-based (WB) dosing or non-weight-based (NWB) dosing of diltiazem is associated with improved outcomes in this population.

Methods: This was a retrospective chart review comparing a WB dosing strategy to a NWB strategy of diltiazem in patients with obesity presenting with AF RVR. Doses were considered WB if they fell within 0.25 to 0.35 mg/kg. Patients in the emergency department (ED) or intensive care unit were eligible for inclusion if they received a dose of intravenous diltiazem for AF RVR and were defined as obese based on a BMI of at least 30 kg/m2 or a weight of at least 100 kg. The primary outcome was the achievement of rate control, defined as a heart rate (HR) less than 110 beats per minute (bpm) within 30 minutes of diltiazem administration. Secondary outcomes included time to achievement of rate control, lowest HR within 30 minutes of diltiazem administration, percent reduction in HR, need for additional medications, and rates of hypotension and bradycardia.

Results: The final population included 61 patients who received WB diltiazem and 148 patients who received NWB diltiazem. The median initial dose of diltiazem was 25 mg (IQR 20-25) in the WB group and 15 mg (IQR 10-20) in the NWB group (p < 0.001). The primary outcome was evaluated in 43 patients in the WB group and 73 patients in the NWB group based on available documentation. Of these patients, 72% in the WB group achieved rate control compared to 68% in the NWB group (p = 0.683). For the secondary outcomes, time to achievement of rate control was significantly shorter in the WB group (median 16 min vs 35 min; p = 0.002). No differences were found for the remainder of the secondary outcomes.

Conclusions: This data adds information regarding dosing in the obese patient, suggesting that WB diltiazem may result in a faster time to rate control with no difference in adverse events. Further trials are needed to fully establish the effect of WB diltiazem in obese patients in AF RVR on outcomes such as ED discharge and length of stay.