Is the Watchman Procedure Safe? Risks and Alternatives

The Watchman procedure is generally considered safe, with serious complication rates that have dropped substantially as the device and implanting techniques have improved. In the largest real-world registry to date, covering more than 97,000 patients who received the current-generation Watchman FLX, the key safety event rate was under half a percent, and successful implantation occurred in about 98% of cases.¹ That said, it is a catheter-based heart procedure, and it carries real risks both during the operation and in the months afterward. Understanding what those risks actually look like in practice, and how they stack up against the alternative of staying on blood thinners, is the core question for anyone weighing this decision.

Why the Procedure Exists

People with atrial fibrillation (often called AFib) have an irregular heartbeat that lets blood pool in a small pouch on the left side of the heart called the left atrial appendage. Because of the appendage’s shape and its internal ridges, blood can sit there long enough to form clots, which can then travel to the brain and cause a stroke.² The standard treatment is long-term blood thinners like warfarin or newer oral anticoagulants. These drugs work well at preventing strokes, but they also raise the risk of serious bleeding, which can be especially dangerous in older adults, people who fall frequently, or people who have already had a major bleed. The Watchman device is a small, umbrella-shaped plug delivered through a catheter in the groin. Once it seals off the appendage, the idea is that clots can no longer form there, and the patient can eventually stop taking blood thinners altogether.

Who Gets the Procedure

The Watchman is not for everyone with AFib. It is approved for people who have a good reason to avoid long-term anticoagulation. In the large U.S. national registry, the average patient had high stroke risk scores and high bleeding risk scores. About 70% had a history of prior bleeding, with gastrointestinal bleeding being the most common type. Roughly 40% had already had a stroke or a transient ischemic attack. Most patients had more than one reason for the procedure, such as a combination of high stroke risk and a history of major bleeding.³ In other words, the typical Watchman patient is someone already facing significant health challenges, not a low-risk person casually opting out of medication.

Short-Term Procedural Risks

The most talked-about immediate risk is pericardial effusion, which is fluid collecting around the heart. This happens when the catheter or the device irritates or punctures the thin sac surrounding the heart. In the large U.S. registry of the current-generation device, pericardial effusion requiring intervention occurred in about 0.5% of patients at 45 days.¹ A separate registry-based study looking at the earlier-generation device reported the rate at about 1.35%, and found that older age, female sex, and certain procedural factors like the number of delivery sheaths used were independently linked to higher risk.⁴ A single-center study tracking effusions closely found a higher overall rate of about 4%, with most cases appearing within six hours and the majority being clinically relevant. That study also flagged female sex, older age, and baseline use of oral anticoagulation as independent predictors.⁵ The range across studies reflects differences in how aggressively teams look for fluid and how they define “clinically relevant,” but the bottom line is that this complication exists, is usually manageable, and has become less common with the newer device.

Device embolization, where the plug dislodges from the appendage and migrates into the heart or a major artery, is rarer but more dramatic. Factors that contribute include improper sizing, unfavorable anatomy of the appendage, excessive manipulation during placement, and high pressure in the left atrium from conditions like heart failure.⁶ When it does happen, the device can often be retrieved using catheter-based techniques such as snares, biopsy forceps, or basket devices, avoiding open-heart surgery. In the large FLX registry, device embolization occurred in 0.04% of cases, roughly 1 in 2,500 procedures.¹

Long-Term Risks After Implantation

Even after the device is successfully placed and the patient goes home, two complications can develop over the following months and years: device-related thrombus and peridevice leak.

Device-related thrombus (DRT) means a blood clot forms on the surface of the implanted device itself. In a large study of nearly 1,740 patients followed for an average of about four years, DRT showed up in about 3.7% of patients. The finding that mattered most was the downstream risk: patients who developed DRT had roughly three and a half times the rate of stroke or systemic embolism compared with patients who did not.⁷ Predictors included a history of prior stroke, permanent (rather than intermittent) AFib, vascular disease, a larger appendage diameter, and lower heart pumping function. This is a risk that follow-up imaging is specifically designed to catch, and when detected early, it is usually managed by restarting anticoagulation temporarily.

Peridevice leak (PDL) occurs when the device does not form a perfectly tight seal against the appendage walls, allowing a small channel of blood flow to persist around it. Leaks are not rare. In the large FLX registry, about 83% of patients had no detectable leak at 45 days, meaning roughly one in six did have some degree of residual flow.¹ For years, the clinical significance of small leaks was debated. More recent evidence has settled the question: even leaks of 3 mm or less were independently associated with a roughly three-and-a-half-fold increase in ischemic stroke, TIA, or systemic embolism, while any PDL of any size was associated with more than a four-fold increase.⁸ That study is relatively recent, and it has shifted clinical thinking. Many teams are now more aggressive about detecting leaks and intervening when they find them.

How the Newer Device Compares to the Original

The Watchman has gone through a significant generational upgrade. The original Watchman 2.5 was the device used in the landmark clinical trials. The newer Watchman FLX, approved in the U.S. in 2020, has a redesigned frame that allows it to be recaptured and repositioned during the procedure, along with a closed end cap that is meant to reduce clot formation on the device surface and a better seal against the appendage wall.

The improvement shows up clearly in the data. In a study comparing more than 27,000 patients who received each device, the FLX had half the rate of in-hospital major adverse events: 1.35% versus 2.40%. The biggest driver was far fewer pericardial effusions requiring intervention (0.42% versus 1.23%). The FLX was also associated with lower in-hospital mortality (0.12% versus 0.24%), less major bleeding, and fewer device embolizations.⁹ A systematic review and meta-analysis across multiple studies found similar patterns, with the FLX associated with roughly a sevenfold improvement in procedural success and substantially lower rates of device embolism and pericardial effusion.¹⁰ A propensity-matched comparison also showed the FLX had lower rates of both DRT and PDL on follow-up imaging.¹¹ The takeaway is that if you are reading about Watchman complication rates from the original clinical trials (which enrolled patients between 2005 and 2013), those numbers are outdated in a meaningful way.

How It Compares to Staying on Blood Thinners

The pivotal trials comparing the Watchman to warfarin showed that the device was at least as good at preventing the combined outcome of stroke, systemic embolism, and cardiovascular death. The PROTECT AF trial, with five years of follow-up, found the device group had fewer total events, with results meeting criteria for both noninferiority and superiority.¹² The PREVAIL trial, a second randomized trial, met noninferiority on one of its two primary endpoints but not the other at 18 months.¹³ Taken together, the evidence supports that the device is roughly equivalent to warfarin for stroke prevention and gets better relative to warfarin over longer follow-up, partly because it avoids the ongoing bleeding risk that blood thinners carry.

The bleeding story is where the device really shines for the right patient. At five years, one observational study found the Watchman cohort had dramatically lower rates of major bleeding compared with patients on direct oral anticoagulants, along with lower rates of ischemic stroke and TIA.¹⁴ A systematic review and meta-analysis of randomized controlled trials confirmed that the risk of bleeding events was significantly lower in the device group compared with anticoagulants.¹⁵ For a patient whose primary concern is surviving without a devastating bleed from long-term anticoagulation, this trade-off can be worth the procedural risks.

Real-World Outcomes Over Longer Follow-Up

Registry data give a clearer picture of what happens in everyday practice, outside the controlled world of clinical trials. In the large U.S. registry of Watchman FLX patients, the one-year rate of any stroke was 1.5%, ischemic stroke was 1.2%, and major bleeding was 6.4%. All-cause death at one year was 8.2%.¹ A European registry showed similar numbers, with all-cause death at one year of about 11% and disabling or non-disabling stroke each at about 1%.¹⁶ Those mortality figures may seem alarming at first glance, but they reflect the population being treated: elderly patients with multiple health conditions, high stroke risk, and a history of serious bleeding. Much of the mortality at one year is from causes unrelated to the device itself. A Medicare-based analysis found that at five years, death occurred in about 44% and ischemic stroke in about 7%, which again underscores that this is a sick population to begin with.

Alternative Devices

The Watchman is not the only option for closing off the left atrial appendage via catheter. The Amplatzer Amulet, a competing device with a different design (a dual-seal mechanism consisting of a lobe and a disc), received FDA approval in 2024. Head-to-head data exist from the SWISS-APERO randomized trial, which showed comparable results between the two devices overall. However, procedure-related complications were higher with the Amulet, largely driven by more bleeding events around the time of the procedure, while peridevice leaks were less frequent with the Amulet compared to the Watchman.¹⁷

A meta-analysis pooling data from several studies confirmed this pattern: the Amulet had significantly higher odds of procedure-related complications but about 60% fewer peridevice leaks. Stroke, death, major bleeding, and device-related thrombus rates were statistically similar between the two.¹⁸ More recently, three-year results from the SWISS-APERO trial showed a trend toward fewer ischemic events with the Amulet, possibly because of its lower leak rate, though the primary analysis did not reach statistical significance.¹⁹ The choice between devices is often guided by the anatomy of the patient’s appendage, operator experience, and local availability rather than by dramatic differences in overall outcomes.

Surgical closure of the appendage during open-heart surgery is another route entirely. It is not a standalone procedure for most people but is sometimes performed when a patient is already undergoing cardiac surgery such as coronary artery bypass.²⁰ The clinical context is different enough from a catheter-based procedure that direct comparisons are difficult.

Recovery and Follow-Up Imaging

The procedure itself is relatively quick, usually taking under an hour. Recovery is faster than many people expect. Research has shown that same-day discharge after a successful, uncomplicated procedure appears safe, with outcomes similar to patients who stay overnight.²¹ Some centers still keep patients overnight as a precaution, especially for those with higher risk profiles, while others have moved to same-day protocols under moderate sedation rather than general anesthesia, which can simplify the process and improve patient satisfaction.²²

After the procedure, patients typically take a combination of blood thinners and antiplatelet drugs for a few months while tissue grows over the device surface. The exact regimen varies by center and by the patient’s bleeding risk. A follow-up imaging study is usually performed around 45 days to check for device-related thrombus and peridevice leak. The traditional method has been transesophageal echocardiography (TEE), which involves swallowing a probe, but cardiac CT has emerged as an alternative. A meta-analysis found that CT picks up more leaks than TEE, detecting residual flow in roughly 59% of cases versus 35%.²³ Detection of device-related thrombus was similar between the two methods. CT has the advantage of being non-invasive and more comfortable, which matters given that follow-up imaging may need to happen more than once. However, it does involve radiation exposure and contrast dye, so the best imaging approach depends on the patient’s situation.

Cost Over Time

One underappreciated aspect of the Watchman is its long-term economics. The device and procedure carry a substantial upfront cost, but patients who would otherwise take anticoagulant medications indefinitely are paying for those drugs, regular blood monitoring (especially with warfarin), and the treatment of bleeding complications for years. A modeling study found that the Watchman became cost-effective relative to blood thinners by around five to six years and was the dominant strategy (both less expensive and more effective) over a ten-year horizon.²⁴ A separate analysis from Japan reached a similar conclusion, finding the device less costly than both warfarin and newer oral anticoagulants over a lifetime horizon, while also providing more quality-adjusted life years.²⁵ These analyses depend on assumptions about how long patients live and how compliant they would be with medication, but the general direction of the evidence is consistent: the procedure pays for itself over time for patients who are good candidates.

Choosing the Right Imaging for Leak Detection

Given the emerging evidence that even small peridevice leaks matter clinically, the method used to check for them takes on greater importance. An earlier study comparing CT and TEE directly found that about half of patients had some degree of flow around the device on CT, while only a third had detectable leak on TEE. Among patients with a leak on CT, about two-thirds also showed it on TEE. No patient had a large leak (5 mm or more) on either modality, but the discrepancy in detecting smaller leaks was notable.²⁶ CT has also been described as superior for evaluating complex appendage anatomy and for detecting device dislodgement.²⁷ As the field continues to grapple with the clinical significance of small leaks, it would not be surprising to see CT play a larger role in standard follow-up protocols.