In a patient with a history of acute stroke and atrial fibrillation (AF), do you mean that both electrical and chemical cardioversion pose a risk of stroke?

Cardioversion-Related Stroke Risk: Both Electrical and Chemical Methods

Yes, both electrical and pharmacological cardioversion carry equivalent stroke risk in patients with atrial fibrillation, and the anticoagulation requirements are identical for both methods. 1

Evidence for Equivalent Stroke Risk

The 2011 ACC/AHA/ESC guidelines explicitly state: "There is no evidence that the risk of thromboembolism or stroke differs between pharmacological and electrical methods of cardioversion. The recommendations for anticoagulation are therefore the same for both methods." 1

This equivalence is further supported by:

• The 2024 ESC guidelines recommend the same anticoagulation approach for both cardioversion strategies, making no distinction between electrical and pharmacological methods regarding thromboembolic risk 1
• The 2018 CHEST guidelines apply identical anticoagulation protocols to both electrical and pharmacological cardioversion 1

Mechanism of Stroke Risk

The stroke risk from cardioversion is not related to the method used (electrical vs. chemical), but rather to the restoration of sinus rhythm itself. 1, 2 When atrial fibrillation converts to normal sinus rhythm:

• Atrial mechanical function ("atrial stunning") remains impaired for days to weeks after rhythm restoration, regardless of conversion method 1
• Pre-existing thrombi in the left atrial appendage can dislodge when coordinated atrial contraction resumes 2
• This risk exists whether conversion occurs via electrical shock or antiarrhythmic drugs 1

Universal Anticoagulation Requirements

For AF duration >48 hours or unknown duration, both methods require: 1

• At least 3 weeks of therapeutic anticoagulation before cardioversion (conventional approach), OR
• Transesophageal echocardiography to exclude left atrial thrombus with abbreviated pre-cardioversion anticoagulation (TEE-guided approach) 1
• At least 4 weeks of therapeutic anticoagulation after successful cardioversion, regardless of baseline stroke risk 1

For AF duration ≤48 hours: 1

• Anticoagulation should be started at presentation (full-dose LMWH or UFH) and cardioversion can proceed without delay 1
• Post-cardioversion anticoagulation for at least 4 weeks is still required 1

Clinical Implications

The FibStroke registry demonstrated that post-cardioversion strokes account for 6.4% of all strokes in patients with paroxysmal/persistent AF, with median delay of 2 days from cardioversion to stroke 3. Importantly:

• 63% of post-cardioversion strokes occurred in patients not using anticoagulation 3
• The method of cardioversion (electrical vs. pharmacological) was not a distinguishing factor in stroke risk 3

Long-term anticoagulation decisions after cardioversion must be based solely on CHA₂DS₂-VASc score, not on successful rhythm restoration or the cardioversion method used. 1, 4 Approximately 50% of patients experience AF recurrence within 1 year after cardioversion, making stroke risk persistent regardless of apparent rhythm control success 4

Common Pitfall to Avoid

Never discontinue anticoagulation based on successful cardioversion or return to sinus rhythm, regardless of whether electrical or pharmacological cardioversion was used. 1, 4 The stroke risk is determined by the underlying atrial fibrillation diagnosis and CHA₂DS₂-VASc score, not by current rhythm status 4