Intravenous metoprolol versus diltiazem for atrial fibrillation with concomitant heart failure

Atrial fibrillation (Afib) with rapid ventricular response (RVR) is acutely treated with intravenous push (IVP) metoprolol (MET) or diltiazem (DIL). In heart failure (HF) patients, diltiazem is not recommended due to negative inotropic effects. Studies comparing the treatment of atrial fibrillation often exclude HF. Hirschy et al. evaluated HF patients with concomitant Afib with RVR who received IVP metoprolol or diltiazem to determine their effectiveness and safety. They found similar safety and effectiveness outcomes between the two groups.

This retrospective, IRB-approved study evaluated patients presenting to the emergency center (EC) with Afib with RVR and HF from January 1, 2018 to July 31, 2021. Included patients were 18 years of age or older, received IVP metoprolol or diltiazem in the EC, and had a recorded baseline ejection fraction (EF). The primary effectiveness outcome was successful heart rate (HR) control 30 min after treatment with either IVP metoprolol or diltiazem, which was defined as HR <100 beats per minute (bpm). Secondary effectiveness outcomes included HR control 60 min post-IVP and at EC discharge or transfer and HR reduction >20% at 30 min after IVP, 60 min after IVP, and at time of discharge or transfer. Other secondary outcomes included the time to adequate HR control, the total dose of IVP metoprolol or diltiazem given, any additional rate-controlling agents given, and crossover between metoprolol and diltiazem. Safety outcomes included bradycardia, hypotension, shortness of breath, increased oxygen requirements, change in EF, acute kidney injury or renal replacement therapy.

Of 2580 evaluated, 193 patients were included (134 DIL vs. 59 MET) with age 73.3 ± 12.2 years, 63% female. The average EF was 48.2 ± 14.2% and 30% of patients had heart failure with reduced ejection fraction (HFrEF) while 64% had heart failure with preserved ejection fraction (HFpEF). Effective heart rate control 30 min post-IVP was not different between the two groups (55% DIL vs. 41% MET, p = 0.063). DIL effectively controlled HR quicker than MET (13 [9, 125] DIL vs. 27 [5, 50] MET, min, p = 0.009). DIL resulted in greater HR reductions at 30 min (33.2 ± 25.4 DIL vs. 19.7 ± 19.7 MET, bpm, p < 0.001) and at 60 min (31 ± 23.5 DIL vs. 19.6 ± 19.1 MET, bpm, p = 0.002). DIL also more frequently resulted in a HR reduction of 20% or greater at 30 min (63% DIL vs. 27% MET, p < 0.001), 60 min post-IVP (59% DIL vs. 41% MET, p = 0.019), and at time of patient discharge or transfer from the EC (70% DIL vs. 49% MET, p = 0.005). No differences in safety outcomes were identified.

Acute management of patients with Afib with RVR and HF is challenging. While successful rate control at 30 min was not significantly different between diltiazem and metoprolol, IVP diltiazem reduced HR more quickly and reduced HR by 20% or greater more frequently than IVP metoprolol with no safety outcome differences. Further studies are needed to evaluate diltiazem's safety in patients with Afib and HF.