Can cardioversion dislodge a left ventricular (LV) thrombus?

Can Cardioversion Dislodge an LV Thrombus?

Cardioversion in patients with left ventricular (LV) thrombus appears to be safe and is not associated with increased thromboembolic risk, based on the best available evidence. 1, 2

Key Evidence on LV Thrombus and Cardioversion

The primary concern with cardioversion has historically focused on left atrial appendage (LAA) thrombi, not left ventricular thrombi. 3 The distinction is critical because:

• LAA thrombi are an absolute contraindication to elective cardioversion due to well-established stroke risk 3
• LV thrombi have different embolic characteristics and appear to pose minimal risk during cardioversion 1, 2

Clinical Evidence Supporting Safety

Most Recent High-Quality Study (2025)

A retrospective study of 39 patients with documented LV thrombus who underwent cardioversion showed zero embolic complications during 81-day follow-up. 1 Key findings:

• Mean LV ejection fraction was 24% (severely reduced)
• Most thrombi were fixed (92%), with only 8% mobile
• Cardioversion performed for atrial fibrillation/flutter, ventricular arrhythmias, and defibrillator testing
• 74% were on warfarin, 5% on DOACs, and 21% on antiplatelet therapy alone
• Mean interval between echocardiogram and cardioversion was 6 days 1

Supporting Earlier Evidence (2006)

A study of 21 patients with echocardiographic LV thrombus who underwent cardioversion demonstrated no embolic events during up to 1-year follow-up (mean 153 days). 2 Important details:

• Mean ejection fraction 22% (severely reduced)
• 81% were anticoagulated before cardioversion
• Thrombi were apical, laminated (71%) or protruding (29%)
• Cardioversion performed emergently (24%), electively (38%), or during EP study (38%) 2

Mechanistic Rationale

The risk of thrombus dislodgement exists at two distinct time points, but guidelines focus primarily on atrial thrombi:

1. At the moment of cardioversion - the immediate electrical shock could theoretically dislodge thrombus 3
2. During atrial stunning post-cardioversion - when atria regain mechanical contraction days to weeks later, this may pose greater risk for atrial thrombi 3

However, LV thrombi behave differently because:

• The left ventricle maintains mechanical contraction even during atrial arrhythmias
• There is no "ventricular stunning" phenomenon analogous to atrial stunning
• Most LV thrombi are laminated and adherent to areas of akinetic myocardium 1, 2

Clinical Management Recommendations

When LV Thrombus is Present

Proceed with cardioversion when clinically indicated, but ensure:

• Therapeutic anticoagulation is maintained before, during, and after the procedure 1, 2
• Warfarin (INR 2.0-3.0) or DOACs should be continued 1
• Do not delay urgent cardioversion in hemodynamically unstable patients 4

Anticoagulation Strategy

• Continue anticoagulation for at least 4 weeks post-cardioversion regardless of LV thrombus status 3
• Long-term anticoagulation decisions should be based on:
  • Underlying cardiac pathology (typically severe LV dysfunction with LV thrombus)
  • Stroke risk factors (CHA₂DS₂-VASc score if AF present) 5
  • Persistence of LV thrombus on follow-up imaging 1

Pre-Cardioversion Assessment

TEE is NOT required to rule out LV thrombus before cardioversion, as the primary concern is LAA thrombus. 3 However:

• TEE should be performed to exclude LAA thrombus if AF duration >48 hours or unknown, or if inadequate anticoagulation 3
• Transthoracic echocardiography adequately visualizes LV apex for thrombus detection 1, 2

Critical Pitfalls to Avoid

• Do not confuse LV thrombus with LAA thrombus - they have different embolic risks and management 3, 1, 2
• Do not unnecessarily delay cardioversion in patients with LV thrombus who are adequately anticoagulated 1, 2
• Do not discontinue anticoagulation in patients with LV thrombus, as the underlying cardiomyopathy typically requires long-term anticoagulation regardless of cardioversion 1, 2
• Ensure adequate anticoagulation - in one study, 21% of patients with LV thrombus received only antiplatelet therapy, which is suboptimal 1

Limitations and Caveats

• Available evidence consists of small retrospective studies with limited patient numbers (39 and 21 patients) 1, 2
• Mobile LV thrombi were rare in these studies (8-29%), and theoretical risk may be higher with mobile thrombi 1, 2
• Larger prospective studies are needed to definitively establish safety across all LV thrombus subtypes 1, 2
• Guidelines do not specifically address LV thrombus as a contraindication to cardioversion, focusing instead on LAA thrombus 3