Does chemical cardioversion with Cartizem (diltiazem) increase the risk of embolic events in patients with atrial fibrillation (AFib) with rapid ventricular response (RVR) lasting more than 24 hours?

Chemical Cardioversion with Diltiazem and Embolic Risk in AFib >24 Hours

Diltiazem (Cartizem) should NOT be used for chemical cardioversion of atrial fibrillation with RVR lasting more than 24 hours without appropriate anticoagulation due to significant risk of thromboembolism. 1

Understanding the Issue

Diltiazem is not actually a cardioversion agent but a rate control medication. This distinction is critical:

• Rate control: Slows ventricular response while leaving the atrium in fibrillation
• Cardioversion: Converts atrial fibrillation back to sinus rhythm

Key Points About Diltiazem

• Diltiazem is a calcium channel blocker recommended for heart rate control in AFib with RVR 1, 2
• It does not chemically cardiovert patients from AFib to sinus rhythm
• It is effective for controlling ventricular rate but does not terminate the arrhythmia 2

Embolic Risk in AFib >24 Hours

The 2024 ESC guidelines clearly state that early cardioversion (whether chemical or electrical) is not recommended without appropriate anticoagulation or transesophageal echocardiography if AFib duration is longer than 24 hours 1. This recommendation applies to any intervention that might result in cardioversion.

For AFib lasting >24 hours:

• Therapeutic anticoagulation for at least 3 weeks before cardioversion is recommended 1
• If 3 weeks of anticoagulation has not been provided, transesophageal echocardiography is recommended to exclude cardiac thrombus 1
• Oral anticoagulation should continue for at least 4 weeks after cardioversion 1

Appropriate Cardioversion Agents

When pharmacological cardioversion is desired, the guidelines recommend:

• Intravenous flecainide or propafenone (for patients without structural heart disease) 1
• Intravenous vernakalant (excluding patients with recent ACS, HFrEF, or severe aortic stenosis) 1
• Intravenous amiodarone (for patients with structural heart disease) 1

Diltiazem is not included in this list as it is not a cardioversion agent.

Proper Use of Diltiazem in AFib

Diltiazem is appropriately used for:

• Rate control in AFib with RVR 1, 2
• First-line rate control in patients with preserved ejection fraction (>40%) 1
• Patients who need rate control but have contraindications to beta-blockers 2

The typical dosing for diltiazem in AFib with RVR is:

• IV administration: 15-25 mg IV bolus
• Oral maintenance: 60-120 mg TID (or 120-360 mg daily modified release) 2

Clinical Implications

For a patient with AFib with RVR lasting >24 hours:

1. Assess stroke risk using CHA₂DS₂-VASc score
2. Initiate appropriate anticoagulation
3. Use diltiazem for rate control only (not expecting cardioversion)
4. If cardioversion is desired, ensure proper anticoagulation for at least 3 weeks before attempting cardioversion with appropriate agents

Conclusion

Diltiazem is not a cardioversion agent and does not carry embolic risks directly. However, any agent that might inadvertently convert AFib to sinus rhythm in a patient with AFib >24 hours duration without proper anticoagulation would pose a thromboembolic risk. The appropriate approach is to use diltiazem strictly for rate control while ensuring proper anticoagulation based on stroke risk assessment.