Year in Review: Left Atrial Appendage Occlusion (LAAO) and Stroke Prevention
In her 2025 SCAI session titled “Year in Review: Left Atrial Appendage Occlusion (LAAO) and Stroke Prevention,” Dr Jacqueline Saw of Vancouver General Hospital and clinical professor at the University of British Columbia presented the year’s most consequential contributions to the LAAO procedure, from advancements in closure devices to the emerging data from ongoing trials. She also provided an update on the latest guidelines and recommendations for the procedure.
Devices and Registries
Dr Saw began with a summary of the registries collecting the data that will shape the future of LAAO. Much of the information presented was from the National Cardiovascular Data Registry (NCDR), which has tracked over 300,000 LAAO procedures in the United States from its inception to Q3 2024. Notably, the prevalence of US LAAO rose dramatically following the 2015 approval of the WATCHMAN Gen 2.5 device (Boston Scientific), which has now been superseded by its successor, the WATCHMAN FLX. Since its approval in 2020, the FLX has demonstrated superior safety compared with the 2.5 in terms of major adverse events, mortality, pericardial effusion, major bleeding, cardiac arrest, and device embolization.
Further safety validation for the WATCHMAN FLX comes from the HEAL-LAA registry, a post-marketing study involving 500 patients across 32 centers. The registry reports a 96.4% successful implantation rate, with imaging at 45 days and 12 months showing complete closure in 85% of patients and a device-related thrombus rate of 2.7% at 1 year. The study also tested the TruSteer delivery sheath; in a 200-patient cohort, the device was implanted successfully in 99.5% of patients without increased complications despite its larger size.
Next up was the WATCHMAN FLX Pro, the focus of the SURPASS Pro Registry. This iteration is distinguished by the addition of HEMOCOAT technology, 3 new radiopaque markers, and a larger size of 40 millimeters, which makes the LAAO procedure accessible to a greater range of anatomies. Using data from the NCDR LAAO Registry, SURPASS Pro analyzed over 21 000 patients who were implanted with the WATCHMAN FLX Pro between October 2023 and June 2024. The device demonstrated a high procedural success rate of 96.9% and very low complication rates, including a 0.4% pericardial effusion rate and a 0.2% all-stroke rate at 45 days.
On the other hand, the competitor in this space, the Amulet device (Abbott), is not seeing as many recent gains. The EMERGE LAA study evaluated the early postapproval experience with the Amulet in the United States, enrolling patients implanted with the Amulet from August 2021 to December 2022. While the study demonstrated improvements over the prior Amulet IDE study at 45 days postoperative, the risk of pericardial effusion requiring intervention remained higher than that associated with the WATCHMAN FLX Pro (1.9% vs 0.4%). Important to consider is that the success rate was higher and the pericardial effusion rate was lower (1%) for operators with more experience (< 30 cases), though neither still met the level of the FLX Pro. The next generation of the Amulet will be the focus of the VERITAS study, which will take place at up to 40 sites across the US, Canada, and Europe.
Ongoing Trials
There are several ongoing randomized controlled trials that are shaping the next generation of LAAO therapy. Of particular interest are CHAMPION and CATALYST, both enrolling patients who are eligible for oral anticoagulant: CHAMPION is randomizing patients to the WATCHMAN FLX vs direct oral anticoagulants (DOACs), and CATALYST is randomizing patients to the Amulet vs DOACs. These results will illuminate the safety and efficacy of LAAC with either of these devices compared with the current standard-of-care DOAC. Data for CHAMPION should be available in 2026. In a later interview, Dr Saw noted that the results of these 2 trials could potentially tip all guidelines to Class 1 for the LAAO procedure.
She also touched on OPTION, which was presented in 2024 and compared WATCHMAN FLX to OAC in 1600 patients undergoing atrial fibrillation (AF) ablation. In this randomized one-to-one trial, WATCHMAN FLX demonstrated non-inferiority for the primary efficacy endpoints of stroke, mortality, and systemic embolization, as well as statistical superiority for non-procedural bleeding at 3 years.
Two other important trials that just launched in the past year or so are the LAAOS-4 and the SIMPLAAFY. Building upon the data from LAAOS-3 showing that surgical LAAO reduced stroke on top of OAC—and the fact that DOAC does not reduce all strokes—, LAAOS-4 will randomize high-risk patients to WATCHMAN FLX plus OAC vs OAC alone. SIMPLAAFY will evaluate patients implanted with the FLX Pro to determine if the new HEMOCOAT technology can reduce the need for aggressive anticoagulation therapies. It will include 3 arms of randomization: aspirin alone, reduced-dose DOAC, and DAPT.
Guidelines and Recommendations
Dr. Saw concluded with updates to the 2023 ACC/AHA guidelines, which now offer a Class 2A recommendation for LAAO in AF patients at a high risk of stroke with non-reversible contraindications to OAC. However, it falls under Class 2B if there is major bleeding that is not necessarily irreversible. In comparison is the surgical indication, which is Class 1 for patients undergoing cardiac surgery with a CHA₂DS₂-VASc score of 2 or greater, but with the addition of OAC patients undergoing surgical LAAC.
She also highlighted the SCAI Expert consensus statement on LAAC, published in 2023, which recommends patients for LAAC if they have non-valvular AF and high thromboembolic risk, but are not suitable for long-term OAC. These patients should have a life expectancy of at least 1 year and a quality of life to benefit from LAAC. Patient-provider discussion for shared decision making should be involved as well. The statement also featured recommendations for providers: physicians performing LAAC and interventional imaging physicians should have sufficient prior experience, and implanting physicians should maintain their skills by performing regular procedures over each 2-year period.
Next on the horizon are the 2025 SCAI/HRS Guidelines, which are currently under executive review and slated for publication in June 2025.
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Any views and opinions expressed are those of the author(s) and/or participants and do not necessarily reflect the views, policy, or position of the Journal of Invasive Cardiology or HMP Global, their employees, and affiliates.
