Is diltiazem (calcium channel blocker) used for rhythm control in atrial fibrillation?

Diltiazem for Rhythm Control in Atrial Fibrillation

Diltiazem is NOT used for rhythm control in atrial fibrillation but is specifically indicated for rate control. 1

Rate Control vs. Rhythm Control

Diltiazem belongs to the class of non-dihydropyridine calcium channel blockers that are used in the management of atrial fibrillation for rate control purposes only. Here's why:

Mechanism of Action and Clinical Role

• Diltiazem slows AV node conduction and increases AV node refractoriness 1
• It effectively reduces ventricular response rate in atrial fibrillation but does not convert AF to sinus rhythm
• It has no direct effect on atrial tissue that would terminate or prevent atrial fibrillation

Guidelines-Based Evidence

The 2014 AHA/ACC/HRS guidelines clearly position diltiazem as a rate control agent:

• "Nondihydropyridine calcium antagonists, such as diltiazem, should be used with caution in those with depressed EF because of their negative inotropic effect" 1
• "For those with HF and preserved EF, nondihydropyridine calcium antagonists can be effective for achieving rate control" 1

Appropriate Use of Diltiazem in AF Management

Indications for Diltiazem

• First-line agent for rate control in patients with preserved ejection fraction 1
• Recommended when beta-blockers are inadequate or contraindicated 1
• Particularly effective for rate control during both rest and exercise 1

Clinical Considerations

• Dosing: Initial IV dose 15-20 mg (0.25 mg/kg) over 2 minutes; may give additional 20-25 mg in 15 minutes if needed 1
• Low-dose strategy: Starting with ≤0.2 mg/kg may provide similar efficacy with reduced hypotension risk 2
• Transition to oral therapy: Can effectively transition from IV to oral long-acting diltiazem (typically 300 mg/day) 3

Contraindications and Cautions

• Avoid in heart failure with reduced ejection fraction due to negative inotropic effects 1
• Use with caution in combination with beta-blockers due to risk of bradycardia 1
• May cause hypotension, especially at higher doses 2

Drugs Actually Used for Rhythm Control

For rhythm control (converting to and maintaining sinus rhythm), the following agents are recommended:

• Amiodarone
• Flecainide
• Propafenone
• Sotalol
• Disopyramide 1

Clinical Decision Algorithm

1. Determine management strategy:

   • Rate control strategy: Use diltiazem (if preserved EF)
   • Rhythm control strategy: Use antiarrhythmic drugs (NOT diltiazem)

2. For rate control with diltiazem:

   • Confirm preserved ejection fraction
   • Start with appropriate dose based on hemodynamic stability
   • Monitor for hypotension and bradycardia
   • Consider combination with digoxin for enhanced rate control 1

3. If rhythm control is desired:

   • Choose appropriate antiarrhythmic drug based on cardiac structure and comorbidities
   • Consider electrical cardioversion
   • Do NOT use diltiazem for this purpose

Bottom Line

Diltiazem is exclusively a rate control agent in atrial fibrillation management and has no role in rhythm control (conversion to or maintenance of sinus rhythm). For rhythm control, specific antiarrhythmic medications or electrical cardioversion should be used instead.