Can a Left Atrial Appendage Clot Become Infected?
Yes, left atrial appendage clots and LAA closure devices can become infected, though this is a rare but serious complication with significant mortality risk.
Evidence for LAA Device Infection
The most direct evidence comes from device-related infections rather than native thrombus infections:
- LAA closure device infections occur with a median time of 6.6 months post-implantation (range 0.2-36 months), carry a 25% mortality rate, and most commonly involve Staphylococcus aureus as the causative organism 1
- Transesophageal echocardiography is diagnostic in all cases of LAA device infection, and PET/CT can provide additional diagnostic utility 1
- Device removal is recommended in appropriate cases, as antibiotic therapy alone should only be considered in selected patients with poor surgical candidacy 1
Pathophysiology Supporting Infection Risk
The left atrial appendage environment creates conditions conducive to both thrombosis and potential infection:
- The LAA is the primary site of thrombus formation in atrial fibrillation, accounting for approximately 90% of cardioembolic strokes in non-valvular AF 2
- LAA flow velocities are significantly reduced due to loss of organized mechanical contraction during AF, creating stagnant blood flow that predisposes to thrombus formation 3
- Spontaneous echo contrast and thrombi in the LAA are independent risk factors for further thrombus formation and embolic events 3
Clinical Implications and Management
When LAA thrombus is identified:
- Anticoagulation with warfarin (target INR 2.5-3.5) is recommended until thrombus resolution is documented by repeat TEE 3
- Among patients with mitral stenosis and left atrial thrombus on TEE, warfarin therapy results in 62% thrombus disappearance over an average of 34 months 3
- Predictors of thrombus resolution include NYHA functional class II or better, LAA thrombus size <1.6 cm², less dense spontaneous echocardiographic contrast, and INR ≥2.5 3
Critical Diagnostic Considerations
- Obliterated or occluded LAA from prior surgical closure can mimic thrombus on echocardiography, making surgical history essential to avoid misdiagnosis and unnecessary anticoagulation 4
- TEE provides sensitivity of 93-100% and specificity of 99% for detecting LAA thrombi 2
- Contrast-enhanced cardiac CT and CMR also provide highly diagnostic (99%) detection of LAA thrombi 2
Key Clinical Pitfalls
- Do not assume all echo-dense material in the LAA represents thrombus—obtain detailed surgical history to distinguish between thrombus and surgically occluded LAA 4
- If LAA device infection is suspected, pursue aggressive diagnostic workup including TEE and consider PET/CT, as mortality reaches 25% even with treatment 1
- Device removal should be strongly considered rather than antibiotics alone, except in patients with prohibitive surgical risk 1