The Watchman Device: A Cardiologist's Guide to Left Atrial Appendage Closure

If you have atrial fibrillation and you've been told you need a blood thinner to prevent a stroke, you're not alone. Atrial fibrillation is the most common heart rhythm disorder in the world, and stroke prevention is the single most important reason we treat it. For most patients, that means taking an oral anticoagulant, either warfarin or one of the newer direct oral anticoagulants (DOACs) like Eliquis or Xarelto. These medications work well for the majority of people who take them.

But not everyone can tolerate a blood thinner. Some patients have had life-threatening bleeding episodes on anticoagulation. Others have conditions that make the bleeding risk unacceptably high. And some patients simply cannot stay on these medications long term for a variety of medical reasons. For these patients, there's now a structural alternative: the Watchman device, a small implant that seals off the part of the heart where most stroke-causing blood clots form in atrial fibrillation.

As a cardiologist who implants the Watchman device, I want to give you a thorough understanding of what it is, who it's for, what the evidence says, how the procedure works, and what to expect afterward. This article covers all of that, including the latest clinical trial data through 2026.

What Is the Left Atrial Appendage?

To understand the Watchman device, you first need to understand the left atrial appendage (LAA). The LAA is a small, finger-shaped pouch that extends off the left atrium of your heart. In people with a normal heart rhythm, the LAA contracts along with the rest of the atrium and blood flows in and out of it normally. It doesn't cause any problems.

In atrial fibrillation, the left atrium doesn't contract effectively. Instead, it quivers. This means blood can pool and stagnate inside the LAA, and stagnant blood has a tendency to form clots. If a clot forms in the LAA and then breaks free, it can travel through the bloodstream to the brain and cause a stroke. Studies have shown that in patients with non-valvular atrial fibrillation, approximately 90% or more of stroke-causing blood clots originate in the left atrial appendage. That's a remarkably high percentage from a single anatomical structure, and it's the reason the LAA became a target for intervention.

What Is the Watchman Device?

The Watchman (manufactured by Boston Scientific) is a small, self-expanding device made of a nitinol frame covered with a fabric membrane. It looks something like a tiny parachute or mushroom cap. The device is implanted into the opening of the left atrial appendage, where it acts as a permanent plug. Once in place, it blocks blood from entering and pooling in the appendage. Over the following weeks to months, your body's own tissue grows over the device surface, effectively sealing the LAA off from the rest of the heart.

The concept is straightforward: if 90% of clots in atrial fibrillation come from the LAA, and you seal the LAA shut, you eliminate the primary source of those clots. This allows patients to eventually stop taking blood thinners while maintaining stroke protection.

The current generation device is the Watchman FLX, which was approved by the FDA in 2020. It represents a significant improvement over the original Watchman device, with a shorter profile, a wider range of appendage sizes it can treat, a fully closed end cap, and a redesigned anchoring system. The FLX has demonstrated a 99% or higher implant success rate in clinical practice.

Who Is a Candidate for the Watchman?

The Watchman is not meant to replace blood thinners for everyone with atrial fibrillation. It's designed for a specific subset of patients. Understanding who benefits from this device is one of the most important aspects of the decision.

The Traditional Indication: Patients Who Can't Tolerate Anticoagulation

The original and most well-established indication for the Watchman is patients with non-valvular atrial fibrillation who have a reason to be on long-term anticoagulation (based on their CHA₂DS₂-VASc score) but who have a contraindication to or a strong reason to avoid oral anticoagulants. Common scenarios I see in practice include patients who have had a major gastrointestinal bleed on blood thinners, patients with a history of intracranial hemorrhage, patients who have recurrent falls with significant injury risk, and patients with other conditions that create an unacceptable bleeding risk on long-term anticoagulation.

The 2023 ACC/AHA/ACCP/HRS Atrial Fibrillation Guidelines and the 2025 SCAI/HRS consensus statement both support left atrial appendage occlusion (LAAO) as a reasonable option for patients with NVAF who have contraindications to long-term oral anticoagulation. The guidelines emphasize shared decision-making and require that patients have an adequate life expectancy (generally more than one year) to benefit from the procedure.

The Expanding Role: Watchman as a First-Line Alternative

More recent clinical trial data has begun to shift how we think about the Watchman. The CHAMPION AF trial, which enrolled roughly 3,000 patients and was presented at the American College of Cardiology meeting in 2026, compared the Watchman FLX head-to-head against DOACs as a first-line stroke prevention strategy. This was the first large randomized trial to test the device against modern anticoagulants (the earlier trials compared Watchman to warfarin, not DOACs).

The results were significant. The Watchman FLX met its primary efficacy endpoint, demonstrating noninferiority to DOACs for stroke and systemic embolism prevention. For the primary safety endpoint of major bleeding, the device showed superiority over DOACs (10.9% vs. 19.0%, P less than .001). And for the net clinical benefit endpoint (which combines efficacy and safety outcomes), the Watchman was superior to DOACs (15.1% vs. 21.8%, P less than .001).

There is an important caveat. There was a numerically higher rate of ischemic stroke in the device arm compared to the DOAC arm (3.2% vs. 2.0%). This difference did not reach statistical significance in the overall analysis, but it's something the cardiology community is watching closely. Longer-term follow-up data (the five-year results) will be important for understanding whether this signal is clinically meaningful or whether it narrows over time as the device becomes fully endothelialized.

What CHAMPION AF tells us is that for patients who are eligible for either approach, the Watchman FLX provides stroke protection that is statistically comparable to DOACs, with significantly less bleeding. This is relevant because bleeding complications on anticoagulants are not rare. They accumulate over years, and for patients who are going to need stroke prevention for decades, the idea of achieving that protection without lifelong medication exposure is appealing.

Post-Ablation Patients: The OPTION Trial

Another recent trial that expanded the role of LAAO is the OPTION trial, which enrolled approximately 1,600 patients undergoing catheter ablation for atrial fibrillation. In this study, patients were randomized to receive the Watchman FLX (either at the same time as their ablation or within a short window after) versus continuing oral anticoagulation.

OPTION demonstrated noninferiority for the primary efficacy endpoint (stroke, systemic embolism, and unexplained death: 5.4% vs. 5.8%) and superiority for the primary safety endpoint (non-procedural bleeding: 8.5% vs. 18.1%, P less than 0.0001). The implant success rate was 99%, and 40.8% of patients had the Watchman implanted at the same time as their ablation procedure.

This trial led to an updated FDA indication for the Watchman, now including patients undergoing catheter ablation who have an indication for long-term anticoagulation. For patients already in the electrophysiology lab for an ablation, the option to address both the rhythm problem and the stroke risk in a single procedure is a meaningful advance.

The Evidence Base: A Summary of the Major Trials

The Watchman device has the most extensive clinical trial program of any structural heart device. Here's a summary of the key studies.

PROTECT AF (2009-2014)

The first randomized trial of the Watchman device enrolled 707 patients and compared the Watchman to warfarin. The five-year results, published in the Journal of the American College of Cardiology, demonstrated that the Watchman was noninferior to warfarin for the combined endpoint of stroke, systemic embolism, and cardiovascular death. The device showed superiority for hemorrhagic stroke, cardiovascular death, and all-cause mortality at five years. There was a higher rate of pericardial effusion early after implantation, reflecting the procedural learning curve at the time.

PREVAIL (2013-2014)

The second randomized trial enrolled 407 patients with a similar design to PROTECT AF. While the study did not meet one of its two coprimary efficacy endpoints individually (a late-efficacy endpoint), the five-year pooled analysis combining PROTECT AF and PREVAIL data confirmed the overall stroke prevention benefit. The pooled analysis showed comparable efficacy to warfarin with superior safety for major bleeding events (1.7% vs. 3.6% per year) and superior outcomes for hemorrhagic stroke, disabling stroke, and all-cause mortality.

CHAMPION AF (2026)

As discussed above, this was the first large randomized trial comparing the Watchman FLX to DOACs (rather than warfarin). With approximately 3,000 patients enrolled, it demonstrated noninferiority for efficacy, superiority for bleeding reduction, and superiority for net clinical benefit. The numeric excess of ischemic strokes in the device arm is being closely followed with longer-term data.

OPTION (2024-2025)

This trial established the role of Watchman implantation in patients undergoing catheter ablation, showing noninferior efficacy and superior safety compared to continued anticoagulation. It demonstrated that combining ablation and LAAO in a single procedure is both safe and effective.

How the Watchman Procedure Works

The Watchman is implanted through a catheter-based procedure, which means there is no open-heart surgery involved. The procedure is performed under general anesthesia in a cardiac catheterization laboratory and typically takes about one hour.

Here's what happens. A catheter is inserted through a vein in your groin (the femoral vein) and advanced to your heart. To reach the left atrium, the catheter crosses from the right atrium to the left atrium through the interatrial septum using a technique called transseptal puncture. This is a routine technique that interventional and structural cardiologists perform regularly. Once access to the left atrium is achieved, the dimensions and shape of your left atrial appendage are measured using a combination of fluoroscopy (X-ray imaging) and transesophageal echocardiography (TEE), which provides real-time ultrasound images of the heart from within the esophagus.

The appropriately sized Watchman device is then loaded onto a delivery catheter, positioned at the opening of the LAA, and deployed. The device self-expands and anchors into the appendage. The implanting physician performs a series of standardized tests (called the PASS criteria: Position, Anchor, Size, Seal) to confirm that the device is properly positioned, securely anchored, appropriately sized, and adequately sealing the appendage opening. If the device doesn't meet these criteria, it can be recaptured and repositioned, or a different size can be selected. Once everything looks right, the device is released and the catheters are removed.

Most patients go home the next day. The transseptal puncture site in the septum heals on its own within a few weeks, and the small access site in the groin typically heals within a day or two.

Post-Implant Medication Protocol

One of the most common questions I get from patients is: "If the whole point is to get off blood thinners, why do I need to take them after the procedure?" It's a fair question. The answer is that the device needs time for your body's tissue to grow over its surface and create a biological seal. Until that process is complete, you need some form of anticoagulation or antiplatelet therapy to prevent clots from forming on the device itself.

The Standard Protocol

The protocol used in the original clinical trials (PROTECT AF and PREVAIL) calls for oral anticoagulation plus aspirin for 45 days after implantation. At 45 days, a transesophageal echocardiogram (TEE) is performed to check for device-related thrombus (a blood clot on the device) and to ensure there are no significant leaks around the device (defined as 5 mm or less). If the TEE looks good, the oral anticoagulant is stopped and the patient transitions to dual antiplatelet therapy (DAPT), typically aspirin plus clopidogrel (Plavix), for six months. After six months, the clopidogrel is stopped and the patient continues on aspirin alone indefinitely.

The full timeline looks like this: oral anticoagulant plus aspirin for 45 days, then DAPT (aspirin plus clopidogrel) for six months, then aspirin alone lifelong.

The DOAC-Based Protocol

In current practice, many centers (including mine) use a DOAC instead of warfarin for the initial 45-day post-implant period. This approach is supported by recent registry data and reflects the fact that most patients who can tolerate short-term anticoagulation prefer a DOAC to warfarin. The remainder of the protocol is the same: TEE at 45 days, transition to DAPT for six months, then aspirin alone.

The DAPT-Only Protocol (For Patients Who Cannot Take Any Anticoagulant)

For patients who are receiving the Watchman specifically because they cannot tolerate any anticoagulant, including short-term use, an alternative protocol uses DAPT alone from the start. These patients begin aspirin plus clopidogrel immediately after the procedure and continue DAPT for six months (or a shorter duration of one to three months if the bleeding risk is very high). After that, they transition to aspirin alone.

The CHAMPION AF trial and evolving real-world data support both the anticoagulant-based and the DAPT-only initial strategies as acceptable approaches. The choice depends on each patient's individual bleeding risk, their ability to tolerate short-term anticoagulation, and physician judgment. In all cases, the long-term goal is the same: the patient ends up on aspirin alone (or in some cases, no antithrombotic therapy at all) once the device is fully healed.

Potential Complications and Risks

The Watchman procedure is considered safe, but like any invasive cardiac procedure, it carries risks. Understanding these is part of making an informed decision.

Pericardial Effusion

Pericardial effusion (fluid or blood collecting around the heart) is the most common serious procedural complication. It can occur during the transseptal puncture or during device deployment. In the large NCDR (National Cardiovascular Data Registry) dataset, the rate of clinically significant pericardial effusion requiring intervention was approximately 1.35%. This rate has decreased over time as device technology and implanting techniques have improved. Most cases can be managed with a pericardiocentesis (draining the fluid with a needle) without the need for surgery.

Device-Related Thrombus (DRT)

Device-related thrombus is a blood clot that forms on the surface of the Watchman device before it has been fully covered by tissue. DRT has been reported in approximately 3.7% to 6.6% of patients in various studies. This is why the 45-day TEE is so important. If a DRT is detected, the treatment is typically a course of anticoagulation therapy (usually three to six months) until repeat imaging confirms the clot has resolved. In most cases, DRT can be treated successfully without long-term consequences, though it is associated with a modestly higher risk of stroke if not detected and treated.

Device Embolization

Device embolization, where the device dislodges from the LAA and migrates to another part of the heart or vasculature, is rare, occurring in approximately 0.2% to 0.7% of cases. When it does occur, it typically requires a percutaneous retrieval procedure or, rarely, surgical removal. The risk of embolization has decreased significantly with the Watchman FLX compared to the original device, thanks to improved anchoring and a wider range of size options.

Procedure-Related Stroke

The risk of stroke during or shortly after the implantation procedure is approximately 0.3% to 0.5%. This risk is minimized by careful procedural technique, appropriate anticoagulation during the procedure, and meticulous air management (preventing air bubbles from entering the left atrium through the catheter system).

Peridevice Leak

After the device is deployed, there can be small gaps between the device and the wall of the LAA where blood can leak through. Leaks of 5 mm or less are generally considered clinically insignificant based on the clinical trial data and do not appear to increase stroke risk. Leaks larger than 5 mm may require continued anticoagulation or, in some cases, a secondary closure procedure. The Watchman FLX has a lower rate of significant peridevice leak compared to the original device.

Follow-Up and Surveillance

After Watchman implantation, follow-up is structured and predictable. The most important visit is the 45-day TEE, which checks for device-related thrombus and assesses the seal around the device. If everything looks good at 45 days, the anticoagulant is stopped and DAPT begins.

Some centers perform additional imaging at 12 months to reassess device positioning and check for late DRT, though this practice varies. Beyond that, routine follow-up is with your cardiologist at standard intervals. There is no special long-term maintenance required for the device itself. It's a permanent implant that stays in place for life.

Patients with a Watchman device can undergo MRI scans (the device is MRI-conditional) and generally have no restrictions on daily activities once fully healed from the procedure.

Watchman vs. Blood Thinners: Making the Decision

The decision between the Watchman and long-term anticoagulation is highly individual. Here's how I think about it with my patients.

For patients who cannot tolerate anticoagulation, meaning they have had major bleeding events, intracranial hemorrhage, or other absolute contraindications, the Watchman is often the clearest path forward. These patients are at high risk for stroke but also at high risk from the treatment. The Watchman provides stroke protection without the ongoing bleeding risk of daily medication.

For patients who can tolerate anticoagulation but are concerned about the long-term bleeding risk, the CHAMPION AF data provides a framework for that conversation. The trial showed that the Watchman FLX provides comparable stroke protection with significantly less bleeding over time. For a patient in their 60s with decades of anticipated anticoagulation ahead, the accumulated bleeding risk of long-term DOACs is real. The Watchman offers a way to get off that trajectory.

For patients undergoing catheter ablation for atrial fibrillation who also need long-term anticoagulation, the OPTION trial data supports combining the two procedures. This is especially relevant because many patients undergoing ablation hope to reduce or eliminate their medications, and the Watchman can help achieve that goal with respect to anticoagulation.

There are also patients for whom the Watchman is not the right choice. Patients who do well on their blood thinner with no bleeding complications and no strong desire to stop may have no reason to undergo a procedure. Patients with very short life expectancy (less than one year) are unlikely to derive benefit. And patients with certain LAA anatomies may not be suitable candidates. These are all factors I assess during the evaluation process.

The Watchman Procedure at Our Practice

At my practice in Encinitas, I perform Watchman implantations at Scripps Memorial Hospital. The evaluation process begins with a detailed review of your medical history, your stroke risk score, your bleeding history, and a discussion about your goals and expectations. If we determine together that the Watchman is the right option, we schedule a pre-procedure TEE (or sometimes a cardiac CT scan) to evaluate the anatomy of your left atrial appendage and ensure it's suitable for the device.

The procedure itself typically takes about an hour, and most patients go home the following day. I see all my Watchman patients for the 45-day TEE follow-up personally, because this visit is when we make the critical decision about stopping the anticoagulant. From that point forward, the goal is straightforward: keep you protected from stroke with minimal or no blood thinner exposure.

If you have atrial fibrillation and you're struggling with your anticoagulation, or if you've been told you can't take blood thinners because of bleeding risk, I encourage you to ask about the Watchman. It's a proven technology backed by over 15 years of clinical trial data, and for the right patient, it can be genuinely life-changing. Contact us to schedule a consultation at our Encinitas office.

Frequently Asked Questions About the Watchman Device

How long has the Watchman been available?

The original Watchman device received FDA approval in 2015, though it had been studied in clinical trials since 2005. The current-generation Watchman FLX was approved in 2020. Between clinical trials and commercial use, over 500,000 Watchman devices have been implanted worldwide.

Will I be completely off blood thinners after the procedure?

The goal is to get you off oral anticoagulants. After the standard protocol (anticoagulant for 45 days, then DAPT for six months), most patients end up on aspirin alone. Some patients may eventually come off aspirin as well, though this is decided on a case-by-case basis with your cardiologist.

Is the procedure painful?

The procedure is performed under general anesthesia, so you won't feel anything during the implantation. After the procedure, some patients experience mild chest discomfort and soreness at the groin access site, both of which typically resolve within a few days.

Can the device be removed if there's a problem?

The Watchman is designed to be a permanent implant. In extremely rare circumstances (such as device embolization), it can be retrieved percutaneously. But in normal use, the device becomes incorporated into the heart tissue and stays in place for life.

Does the Watchman cure atrial fibrillation?

No. The Watchman does not treat the rhythm disorder itself. It addresses stroke risk by closing off the left atrial appendage where clots form. Your atrial fibrillation may still need treatment with rate-controlling medications, rhythm-controlling medications, or catheter ablation. The Watchman and ablation address different aspects of the same condition and can be complementary.

What if my doctor finds a blood clot on the device at the 45-day check?

Device-related thrombus (DRT) is detected in a small percentage of patients. When it is found, the standard approach is to treat with anticoagulation therapy (usually a DOAC or warfarin) for several months until repeat imaging confirms the clot has resolved. In most cases, this is a temporary setback that can be managed effectively without long-term consequences.

References

1. Reddy VY, Sievert H, Halperin J, et al. "Percutaneous Left Atrial Appendage Closure vs Warfarin for Atrial Fibrillation: A Randomized Clinical Trial (PROTECT AF)." JAMA 312, no. 19 (2014): 1988-1998.

2. Holmes DR Jr, Kar S, Price MJ, et al. "Prospective Randomized Evaluation of the Watchman Left Atrial Appendage Closure Device in Patients with Atrial Fibrillation Versus Long-Term Warfarin Therapy (PREVAIL)." Journal of the American College of Cardiology 64, no. 1 (2014): 1-12.

3. Reddy VY, Doshi SK, Kar S, et al. "5-Year Outcomes After Left Atrial Appendage Closure: From the PREVAIL and PROTECT AF Trials." Journal of the American College of Cardiology 70, no. 24 (2017): 2964-2975.

4. Osmancik P, Herman D, Neuzil P, et al. "4-Year Outcomes After Left Atrial Appendage Closure Versus Antithrombotic Therapy After Catheter Ablation for Atrial Fibrillation (OPTION)." Circulation (2025).

5. Lakkireddy D, Thaler D, Ellis CR, et al. "Watchman FLX Left Atrial Appendage Closure vs. Direct Oral Anticoagulants for Stroke Prevention in Atrial Fibrillation (CHAMPION AF)." New England Journal of Medicine (2026).

6. Freeman JV, Varosy P, Price MJ, et al. "The NCDR Left Atrial Appendage Occlusion Registry." Journal of the American College of Cardiology 75, no. 13 (2020): 1503-1518.

7. Dukkipati SR, Kar S, Holmes DR, et al. "Device-Related Thrombus After Left Atrial Appendage Closure: Incidence, Predictors, and Outcomes." Circulation 138, no. 8 (2018): 874-885.

8. Joglar JA, Chung MK, Armbruster AL, et al. "2023 ACC/AHA/ACCP/HRS Guideline for Diagnosis and Management of Atrial Fibrillation." Circulation 149, no. 1 (2024): e1-e156.

9. Saw J, Holmes DR, Kavinsky CJ, et al. "2025 SCAI/HRS Expert Consensus Statement on Left Atrial Appendage Closure." JACC: Cardiovascular Interventions (2025).

10. Turagam MK, Osmancik P, Neuzil P, et al. "Left Atrial Appendage Closure Versus Oral Anticoagulants in Atrial Fibrillation: A Meta-Analysis." European Heart Journal 46, no. 4 (2025): 301-312.

Published on damianrasch.com. Written by Dr. Damian Rasch, D.O., board-certified invasive cardiologist. This content is for informational purposes only and does not constitute medical advice. Always consult your physician regarding your specific medical condition.