Why is a patient with a Watchman (Left Atrial Appendage Closure Device) still on Dual Antiplatelet Therapy (DAPT)?

Why Patients with Watchman Devices Remain on DAPT

Patients with Watchman devices require dual antiplatelet therapy (DAPT) during the initial post-implantation period to prevent device-related thrombus formation while the device undergoes endothelialization, which takes approximately 45 days to 6 months. 1, 2

Standard Post-Implantation Antithrombotic Protocol

The regulatory-approved regimen following Watchman implantation follows a three-phase approach 1, 3:

• Phase 1 (0-45 days): Warfarin (INR 2.0-3.0) plus aspirin to prevent thrombus formation on the incompletely endothelialized device 1, 3
• Phase 2 (45 days to 6 months): DAPT with aspirin plus clopidogrel after confirming adequate device position and absence of significant peri-device leak on transesophageal echocardiography 1, 3
• Phase 3 (>6 months): Aspirin monotherapy indefinitely 1, 3

Why DAPT is Necessary

Device Endothelialization Timeline

• The Watchman device requires time for complete endothelialization, during which the bare metal surface remains thrombogenic 1, 2
• Device-related thrombus occurs in 2.4-7.2% of patients during the first year, with highest risk during the transition from anticoagulation to antiplatelet therapy 4, 5
• Complete endothelialization typically occurs by 45 days, but additional antithrombotic coverage is maintained through 6 months as a safety margin 1, 3

Risk Factors for Device-Related Thrombus

Your patient may be at particularly high risk if she has 2, 6, 4:

• Non-paroxysmal atrial fibrillation (OR 1.90-2.24 for device thrombus) 2
• Renal insufficiency (OR 4.02) 2
• History of prior stroke/TIA (OR 2.31) 2
• Deep device implantation >10mm from pulmonary vein limbus (OR 2.41) 2
• Premature discontinuation of antithrombotic therapy 4

Clinical Implications and Monitoring

The Paradox of Watchman Therapy

• Critical caveat: The need for post-procedural antithrombotic therapy exposes patients to bleeding risks that may be equivalent to DOACs, creating a paradox for patients who received the device due to bleeding contraindications 1
• This is particularly problematic since the Watchman trials compared against warfarin, not modern DOACs which have bleeding profiles similar to aspirin 1, 3

Mandatory Surveillance Requirements

• TEE at 45 days: Required before transitioning from anticoagulation to DAPT to assess for device-related thrombus and peri-device leak 2, 3
• TEE at 1 year: Required before discontinuing DAPT to aspirin monotherapy 2, 3
• Any peri-device leak detected on TEE is associated with increased thromboembolism risk and may necessitate continued anticoagulation 2, 6

Alternative Regimens in Real-World Practice

Shortened DAPT Protocols

Real-world practice differs significantly from trial protocols 1:

• Some centers use 3 months of DAPT alone (without initial anticoagulation) with comparable safety and efficacy outcomes 7
• DOACs at full or reduced dose have been used as alternatives to warfarin during the initial 45-day period with no increase in device-related thrombus 1, 8
• Observational data support antiplatelet therapy alone without associated increases in device-related thrombus or stroke 1

When to Consider Extended DAPT

Your patient should remain on DAPT beyond 6 months if 1, 2, 5:

• Device-related thrombus is detected on surveillance imaging (requires warfarin reinitiation until resolution, then continued DAPT) 4
• Significant peri-device leak (>5mm) persists on follow-up imaging 2
• She has concurrent coronary artery disease requiring DAPT for stent thrombosis prevention 1

Common Pitfalls to Avoid

• Do not discontinue DAPT before 45-day TEE: This is the highest-risk period for device-related thrombus formation 4, 5
• Do not skip surveillance imaging: Asymptomatic device-related thrombus occurs in 2.4-3.4% of patients and requires treatment 4, 5
• Verify medication adherence: All patients with device-related thrombus in one series had discontinued their prescribed antithrombotic regimen 4
• Recognize that no ischemic strokes occur between 45 days and 4 months when proper antithrombotic therapy is maintained, making the 45-day TEE potentially less critical than the later surveillance 5