From the Guidelines
For a patient with atrial fibrillation with rapid ventricular response (AFib with RVR) who is already taking Metoprolol 25 mg twice daily, I recommend adding diltiazem as an as-needed medication for breakthrough episodes of RVR, as supported by the 2011 ACCF/AHA/HRS focused updates incorporated into the ACC/AHA/ESC 2006 guidelines for the management of patients with atrial fibrillation 1.
Recommended Approach
- Start with diltiazem 30 mg orally as needed when heart rate exceeds 100 beats per minute, with a maximum of 4 doses per day and at least 4 hours between doses.
- Diltiazem works through a different mechanism than metoprolol, blocking calcium channels rather than beta receptors, providing complementary rate control, as noted in the guidelines 1.
Rationale
- The combination approach allows for maintenance of the baseline beta-blocker therapy while addressing breakthrough episodes.
- If the patient experiences frequent need for the as-needed medication, consider discussing with their physician about increasing the standing metoprolol dose or switching to a different rate control strategy.
Monitoring and Precautions
- Monitor for potential side effects including hypotension, bradycardia, or heart block, especially when both medications are active in the system, as cautioned in the guidelines 1.
- Patients should be instructed to check their pulse before taking the as-needed medication and to seek medical attention if they experience dizziness, unusual fatigue, or shortness of breath.
Key Considerations
- The 2011 ACCF/AHA/HRS focused updates incorporated into the ACC/AHA/ESC 2006 guidelines for the management of patients with atrial fibrillation recommend diltiazem as a Class I, LOE B option for heart rate control in patients with AFib 1.
- The guidelines also note that beta blockers, such as metoprolol, are effective for rate control, but may not provide adequate control during exercise, making the addition of diltiazem a reasonable approach 1.
From the FDA Drug Label
Peak digoxin body stores larger than the 8 to 12 mcg/kg required for most patients with heart failure and normal sinus rhythm have been used for control of ventricular rate in patients with atrial fibrillation Doses of digoxin used for the treatment of chronic atrial fibrillation should be titrated to the minimum dose that achieves the desired ventricular rate control without causing undesirable side effects.
The patient is already on Metoprolol 25 twice daily. Digoxin can be used as an as-needed rate control medication for AFib with RVR. The dose should be titrated to the minimum dose that achieves the desired ventricular rate control without causing undesirable side effects 2.
From the Research
As Needed Rate Control Medication for AFib with RVR
If a patient is already on Metoprolol 25 twice daily, the following options can be considered for as needed rate control medication for atrial fibrillation (AFib) with rapid ventricular response (RVR):
- Diltiazem: Studies have shown that diltiazem can achieve rate control faster than metoprolol 3, 4. However, it may have a higher incidence of worsening heart failure symptoms in patients with heart failure with reduced ejection fraction (HFrEF) 5.
- Amiodarone: Although amiodarone is sometimes used for rate control in AFib with RVR, one study found that it had a higher failure rate compared to metoprolol 6.
- Other options: Other medications such as digoxin, procainamide, and calcium channel blockers may also be considered, but their use may be limited by certain clinical conditions or comorbidities 7.
Considerations for Selecting a Medication
When selecting a medication for as needed rate control, clinicians should consider the individual patient's clinical situation, comorbidities, and cardiovascular status 3, 7. The choice of medication may depend on factors such as the presence of heart failure, the patient's hemodynamic stability, and the potential for adverse effects 5.
Key Findings from Studies
- A study published in 2022 found that metoprolol had a lower failure rate than amiodarone and was superior to diltiazem in achieving rate control at 4 hours 6.
- Another study published in 2021 found that there was no difference in sustained rate control between diltiazem and metoprolol, but diltiazem achieved rate control faster 4.
- A study published in 2022 found that diltiazem had a higher incidence of worsening heart failure symptoms in patients with HFrEF, but overall adverse effects were similar between diltiazem and metoprolol 5.