Can ablation cause blood clots even in patients with a Watchman (Left Atrial Appendage Closure) device?

Can Ablation Cause Blood Clots Even With a Watchman Device?

Yes, catheter ablation can cause blood clots even in patients with a Watchman device, as the ablation procedure itself carries independent thrombotic risks separate from the device's protective effects. The Watchman device only addresses thrombus formation in the left atrial appendage, while ablation creates multiple additional thrombogenic mechanisms throughout the left atrium 1.

Mechanisms of Clot Formation During Ablation

Catheter ablation generates thrombi through several distinct pathways that are unrelated to left atrial appendage closure 1:

• Thermal injury effects: Radiofrequency ablation causes tissue boiling and steam pop phenomena, leading to denaturation of plasma proteins and clot formation that can embolize to the cerebrovascular system 1
• Mechanical trauma: Direct catheter manipulation across the atrial septum and within the left atrium creates endothelial injury and activates coagulation cascades 1
• Non-thermal mechanisms: Newer ablation techniques like pulsed field ablation can generate gaseous microbubbles through hydrolysis or nitrogen displacement, which may affect cerebral blood flow 1
• Hemodynamic instability: Blood pressure drops during rapid ventricular tachycardia or pacing can cause cerebral hypoperfusion and ischemic injury 1

Documented Stroke Risk With Ablation

The procedural stroke risk from ablation remains clinically significant regardless of Watchman presence 1:

• Japanese registry data: Cerebral or systemic thromboembolism occurred in 0.2% of all catheter ablation procedures, with AF ablations showing 0.2% risk versus 0.09% for non-AF ablations 1
• Age-related risk: Patients over 85 years had stroke/TIA rates of 1.4% after radiofrequency or cryoballoon ablation 1
• Australia/New Zealand data: 30-day stroke or TIA rate was 0.24% after AF ablation, with 0.11% occurring in-hospital 1

Device-Related Thrombosis Adds Additional Risk

The Watchman device itself carries ongoing thrombotic risk that compounds ablation-related concerns 1:

• Device-related thrombus (DRT) occurs with an incidence of 1.7%–7.2% and is associated with higher ischemic stroke risk 1
• Late detection: DRT can be documented as late as 1 year post-implantation in one-fifth of patients 1
• Peri-device leaks: Small leaks (0–5 mm) are present in approximately 25% of patients and may allow thrombus passage 1

Critical Risk Factors for DRT That May Worsen With Ablation

Specific patient characteristics increase device-related thrombosis risk, which ablation may exacerbate 1:

• Non-paroxysmal AF (OR 1.90–2.24) 1
• Renal insufficiency (OR 4.02) 1
• History of TIA or stroke (OR 2.31) 1
• Deep device implantation >10 mm from pulmonary vein limbus (OR 2.41) 1
• Hypercoagulable disorders (OR 17.5) 1

Combined Procedure Safety Data

Registry data on combined Watchman implantation and catheter ablation procedures demonstrate the dual thrombotic risk 2, 3:

• Acute safety: In 139 patients undergoing concomitant procedures, successful Watchman implantation was achieved in 100%, with a 30-day serious adverse event rate of 8.7% and device/procedure-related SAE rate of 1.4% 2
• Long-term outcomes: At 2-year follow-up of 142 combined procedure patients, ischemic stroke/TIA/systemic thromboembolism occurred at 1.09 per 100 patient-years despite 92% remaining off oral anticoagulation 3
• Pulsed field ablation: A small case series (n=7) showed successful PVI with PFA in patients with pre-existing Watchman devices without major adverse events, though follow-up was limited 4

Anticoagulation Management Paradox

The need for post-ablation anticoagulation creates a clinical dilemma in Watchman patients 1:

• Standard post-Watchman protocols require 45 days of warfarin plus aspirin, followed by 6 months of dual antiplatelet therapy 1
• This exposes patients to bleeding risks that may be equivalent to DOACs, creating a paradox for those who received the device due to bleeding contraindications 1
• No randomized trial data exist showing beneficial effects on ischemic stroke or systemic embolism in patients with AF undergoing left atrial appendage occlusion during catheter ablation 1

Clinical Implications and Monitoring

Mandatory surveillance imaging is essential to detect both device-related and ablation-related thrombotic complications 1:

• TEE should be performed at 45 days and 1 year post-Watchman to evaluate for device-related thrombus and peri-device leaks 5
• High-grade hypoattenuated thickening on cardiac CT is significantly associated with increased stroke risk (HR 4.6) and requires intensified anticoagulation 1
• Late "rule-out" imaging approach is mandated given that DRT can be detected up to 1 year post-implantation 1

Practical Recommendation

For patients with Watchman devices undergoing catheter ablation, maintain heightened vigilance for thrombotic complications through the acute procedural period and ensure adherence to post-procedural anticoagulation protocols despite the presence of the device 1, 2. The Watchman does not eliminate stroke risk from ablation-related thrombus formation in non-appendage locations 1.