What is the treatment for uncontrolled atrial fibrillation (afib) with a rapid ventricular rate of tachycardia at the paramedic level?

From the Guidelines

For uncontrolled atrial fibrillation with a rate of 125 at the paramedic level, the primary treatment is rate control with medication, specifically administering diltiazem or metoprolol IV to reduce the heart rate to below 100 bpm while maintaining blood pressure and improving symptoms. The most recent and highest quality study, 1, published in 2014, recommends a heart rate control strategy for symptomatic management of AF, with a goal of resting heart rate <80 bpm. According to this study, intravenous administration of beta blockers or nondihydropyridine calcium channel antagonists, such as diltiazem, is recommended to slow the ventricular response to AF in the acute setting.

Treatment Options

• Administer diltiazem 0.25 mg/kg IV (typically 15-20 mg) over 2 minutes, which can be repeated at 0.35 mg/kg after 15 minutes if needed, as recommended by 1 and 1.
• Alternatively, metoprolol 5 mg IV given slowly over 2-5 minutes can be used, repeating every 5 minutes for a maximum of 3 doses (15 mg total), as suggested by 1.
• If the patient is unstable with signs of shock or acute heart failure, prepare for synchronized cardioversion starting at 120-200 joules, as recommended by 1.

Monitoring and Support

• Ensure IV access, continuous cardiac monitoring, and frequent vital sign checks.
• Oxygen should be administered if saturation is below 94%, as is standard practice in emergency medicine.
• These medications work by blocking calcium channels (diltiazem) or beta receptors (metoprolol) in the heart, slowing conduction through the AV node and reducing ventricular rate.

Goal of Treatment

• The goal is to reduce the heart rate to below 100 bpm while maintaining blood pressure and improving symptoms, not necessarily converting to normal sinus rhythm at this stage of care, as recommended by 1.

From the FDA Drug Label

Diltiazem slows the ventricular rate in patients with a rapid ventricular response during atrial fibrillation or atrial flutter Diltiazem exhibits frequency (use) dependent effects on AV nodal conduction such that it may selectively reduce the heart rate during tachycardias involving the AV node with little or no effect on normal AV nodal conduction at normal heart rates. Based on this relationship, the mean plasma diltiazem concentration required to produce a 20% decrease in heart rate was determined to be 80 ng/mL. Mean plasma diltiazem concentrations of 130 ng/mL and 300 ng/mL were determined to produce reductions in heart rate of 30% and 40%

For a patient with uncontrolled atrial fibrillation (AFib) and a heart rate of 125, diltiazem (IV) can be used to slow the ventricular rate.

• The goal is to reduce the heart rate by 20-30% to a more manageable level.
• The paramedic should follow the recommended dosing guidelines for diltiazem to achieve the desired effect.
• It is essential to monitor the patient's heart rate, blood pressure, and overall clinical condition closely during treatment with diltiazem 2.

From the Research

Treatment Options for Uncontrolled AFib Rate

• The treatment for uncontrolled atrial fibrillation (AFib) rate of 125 at the paramedic level involves rate control using medications such as metoprolol or diltiazem 3, 4, 5, 6, 7.
• Metoprolol and diltiazem are both commonly used for rate control in AFib, with studies suggesting that they have similar efficacy and safety profiles 3, 4, 5, 6, 7.

Comparison of Metoprolol and Diltiazem

• A study comparing intravenous metoprolol and diltiazem for rate control in AFib found that there was no significant difference in the achievement of rate control between the two medications 3.
• Another study found that metoprolol was associated with a 26% lower risk of adverse events compared to diltiazem, although there was no difference in the rates of bradycardia or hypotension 4.
• A systematic review and meta-analysis found that diltiazem was associated with increased achievement of rate control target compared to metoprolol, although both medications had similar incidence of hypotension and bradycardia 5.

Patient-Specific Factors

• Patient-specific factors such as past history of AF, diabetes mellitus, and prior medication use can influence the choice of β-blocker versus calcium channel blocker therapy for rate control in AFib 7.
• A study found that patients with higher initial heart rates faced higher rates of adverse events, although there was no difference in the rates of bradycardia or hypotension between metoprolol and diltiazem 4.

Safety and Efficacy

• Studies have found that both metoprolol and diltiazem are safe and effective for rate control in AFib, with low rates of adverse events such as hypotension and bradycardia 3, 4, 5, 6, 7.
• A study found that short-term use of diltiazem was likely as safe and effective as metoprolol in the acute management of patients with heart failure with reduced ejection fraction and AFib with rapid ventricular response 6.