Should I use Cardizem (Diltiazem) or Metoprolol intravenous (IV) for atrial fibrillation (afib) with rapid ventricular response (RVR)?

From the Guidelines

For atrial fibrillation with rapid ventricular response (AFib with RVR), Cardizem (diltiazem) is generally the preferred initial treatment for hemodynamically stable patients without heart failure or significant lung disease, due to its effectiveness in controlling heart rate and its relatively favorable side effect profile, as supported by the 2010 American Heart Association guidelines 1.

Key Considerations

• The choice between Cardizem and metoprolol depends on the patient's specific condition, including the presence of heart failure, lung disease, and the underlying cause of the AFib.
• Typical Cardizem IV dosing is 0.25 mg/kg (usually 15-20 mg) over 2 minutes, followed by a second bolus of 0.35 mg/kg (25-30 mg) after 15 minutes if needed, then a maintenance infusion of 5-15 mg/hour, as outlined in the 2010 American Heart Association guidelines 1.
• Metoprolol is generally preferred in patients with heart failure with preserved ejection fraction or if the AFib is triggered by increased sympathetic tone, with typical IV dosing of 5 mg slow IV push over 2-5 minutes, which can be repeated every 5 minutes for a total of 15 mg, as noted in the 2001 ACC/AHA/ESC guidelines 1.

Mechanism and Side Effects

• Both medications work by slowing conduction through the AV node, but through different mechanisms - Cardizem blocks calcium channels while metoprolol blocks beta-adrenergic receptors.
• Avoid Cardizem in patients with heart failure with reduced ejection fraction, hypotension, or pre-excitation syndromes, and avoid metoprolol in patients with severe bronchospastic disease, bradycardia, or high-degree heart block, as cautioned in the 2010 American Heart Association guidelines 1 and the 2001 ACC/AHA/ESC guidelines 1.

Clinical Decision Making

• The decision to use Cardizem or metoprolol should be based on the individual patient's clinical presentation and medical history, taking into account the potential benefits and risks of each medication, as emphasized in the 2010 American Heart Association guidelines 1 and the 2001 ACC/AHA/ESC guidelines 1.
• It is essential to monitor patients closely for signs of adverse effects, such as hypotension, bradycardia, or heart block, and to adjust the treatment plan accordingly, as recommended in the 2010 American Heart Association guidelines 1.

From the Research

Comparison of Cardizem (Diltiazem) and Metoprolol for Atrial Fibrillation with Rapid Ventricular Response

• The efficacy of intravenous (IV) diltiazem and metoprolol in managing atrial fibrillation (AF) with rapid ventricular response (RVR) has been compared in several studies 2, 3, 4, 5, 6.
• A comprehensive umbrella review of systematic reviews and meta-analyses found that IV diltiazem was significantly more successful in rate control for AF with RVR than IV metoprolol, with a risk ratio of 1.30 (95% CI, 1.09-1.56; I2 = 0%; P = .003) 2.
• The same review also found that IV diltiazem led to a significantly greater reduction in ventricular rate, with a mean difference of -14.55 (95% CI, -16.93 to -12.16; I2 = 72%; P < .00001) 2.
• However, IV diltiazem was also associated with a significantly increased risk of hypotension, with a risk ratio of 1.43 (95% CI, 1.14-1.79; I2 = 0%; P = .002) 2.

Time to Rate Control and Sustained Rate Control

• A retrospective chart review found that time to initial rate control was significantly shorter with diltiazem compared to metoprolol (15 min vs. 30 min, respectively, p = 0.04) 6.
• The same review found no difference in sustained rate control between diltiazem and metoprolol (87.5% vs. 78.9%, p = 0.45) 6.
• Another study found that patients considered β-blocker naive were more likely to achieve successful rate control with IV metoprolol compared to patients on chronic β-blocker therapy (56.1% vs 42.4%; P = .03) 5.

Safety Outcomes

• The review of sustained rate control found that neither hypotension nor bradycardia were significantly different between diltiazem and metoprolol groups 6.
• The umbrella review found that IV diltiazem was associated with a significantly increased risk of hypotension, but the review of sustained rate control did not find a significant difference in hypotension between the two groups 2, 6.