From the Guidelines
Non-dihydropyridine calcium channel blockers are recommended for acute atrial fibrillation (AF) management because they effectively control ventricular rate by slowing conduction through the atrioventricular (AV) node, as evidenced by the 2014 AHA/ACC/HRS guideline 1. The two main agents used are verapamil and diltiazem. Diltiazem is typically administered as an IV bolus of 0.25 mg/kg over 2 minutes, followed by a continuous infusion of 5-15 mg/hour, while verapamil is given as 5-10 mg IV over 2-3 minutes, potentially followed by 5 mg after 15-30 minutes if needed. These medications work by blocking L-type calcium channels in the AV node, which decreases conduction velocity and increases the refractory period, effectively reducing the number of atrial impulses that reach the ventricles. This mechanism provides rapid rate control, usually within minutes of administration, without attempting to convert the rhythm back to normal sinus. Some key points to consider when using non-dihydropyridine calcium channel blockers for AF management include:
- They are particularly useful in patients with preserved left ventricular function but should be avoided in those with heart failure or hypotension due to their negative inotropic effects, as noted in the 2011 ACCF/AHA/HRS focused updates 1.
- They should not be used in patients with pre-excitation syndromes like Wolff-Parkinson-White syndrome as they can paradoxically increase ventricular rate by preferentially conducting through accessory pathways, as warned against in the 2014 AHA/ACC/HRS guideline 1.
- The choice between verapamil and diltiazem may depend on specific patient factors, such as the presence of bronchospasm or chronic obstructive pulmonary disease, where non-dihydropyridine calcium channel blockers might be preferred over beta blockers, as suggested in the 2011 ACCF/AHA/HRS focused updates 1. Overall, non-dihydropyridine calcium channel blockers are a valuable option for acute AF management, offering effective rate control with a mechanism that is distinct from beta blockers and other antiarrhythmic agents, as supported by the guidelines 1.
From the FDA Drug Label
Injectable forms of diltiazem are contraindicated in: ... 6. Patients with atrial fibrillation or atrial flutter associated with an accessory bypass tract such as in WPW syndrome or short PR syndrome. The FDA drug label does not answer the question.
From the Research
Non-Dihydropyridine Calcium Channel Blockers in Acute AF Management
- Non-dihydropyridine calcium channel blockers, such as diltiazem and verapamil, are recommended for acute AF management due to their efficacy in rate control 2, 3, 4, 5.
- These medications have a quick onset of action, minimal side effects, and are relatively low in cost 2.
- Studies have shown that diltiazem is associated with increased achievement of rate control target in patients with AF-RVR compared to metoprolol 4, 5.
- The use of non-dihydropyridine calcium channel blockers is also supported by their ability to reduce ventricular rate, particularly at short time intervals after administration 5.
Comparison with Beta-Blockers
- Beta-blockers, such as metoprolol, are also used for rate control in AF, but may have a slower onset of action compared to non-dihydropyridine calcium channel blockers 3, 4.
- Studies have shown that there is no significant difference in sustained rate control between diltiazem and metoprolol 3, but diltiazem may be more effective in achieving rate control target 4, 5.
- The choice of rate control agent may depend on individual patient factors, such as the presence of heart failure or other comorbidities 6.
Safety and Efficacy
- Non-dihydropyridine calcium channel blockers and beta-blockers have been shown to be safe and effective for rate control in AF, with similar incidence of hypotension and bradycardia 4, 5.
- However, the use of non-dihydropyridine calcium channel blockers may be associated with a increased risk of hypotension 5.
- Further studies are needed to determine the optimal rate control strategy for patients with AF and to compare the safety and efficacy of different medications 2, 6, 5.