Real-World Experience With WATCHMAN FLX Replicates Pivotal Trial Outcomes

Routine clinical use of the WATCHMAN FLX left atrial appendage occlusion (LAAO) device for stroke prevention in patients with high-risk nonvalvular atrial fibrillation achieves similar safety and efficacy outcomes through one year as those achieved in the PINNACLE FLX clinical trial, which led to the device’s FDA approval in July 2020.

So found the real-world SURPASS study, involving more than 95,000 patients from the American College of Cardiology’s National Cardiovascular Disease Registry (NCDR) LAAO Registry^™. The study was published online in Circulation: Cardiovascular Interventions (Epub 2024 Jul 26).

“We were most interested in knowing that the WATCHMAN FLX, which is now widely implanted by thousands of different operators, is safe,” says the study’s lead investigator and corresponding author Samir Kapadia, MD, Chair of Cardiovascular Medicine at Cleveland Clinic. “The SURPASS study, with its very large dataset from across the U.S., confirmed that the favorable outcomes we saw in a clinical trial setting are being replicated in the community.”

New device in need of real-world evidence

The WATCHMAN FLX is a second-generation LAAO device that underwent several design changes from the initial WATCHMAN 2.5, which had well-established safety and efficacy. Alterations were designed to address complications, especially peridevice leak and device-related thrombosis, and to ease implantation and treat a wider range of LAA anatomy.

The WATCHMAN FLX demonstrated favorable safety and efficacy in PINNACLE FLX, the 12-month investigational device exemption study involving 400 patients, as well as in smaller studies in Europe and the U.S.

Over the past 10 years, implantation of an LAAO device has become an established stroke prevention option for patients with atrial fibrillation who are poor candidates for oral anticoagulation therapy, and thousands of the devices are implanted monthly in the U.S.

SURPASS was designed to evaluate safety and efficacy outcomes of the WATCHMAN FLX device in routine clinical practice.

Characteristics of the large cohort

The SURPASS cohort consisted of 97,185 patients from the NCDR LAAO Registry who underwent WATCHMAN FLX implantation at 772 U.S. hospitals between August 2020 and September 2022.

Compared with PINNACLE FLX, patients at baseline in the SURPASS study:

• Were older (mean age of 76 ± 8 years vs. 74 ± 8 years)
• Were more likely to be women (41.3% of the cohort vs. 35.5%)
• Had a higher risk profile (mean CHA₂DS₂-VASc risk score of 4.8 ± 1.5 vs. 4.2 ± 1.5, and mean HAS-BLED score of 2.8 ± 1.1 vs. 2.0 ± 1.0).
• Had higher rates of prior stroke (20.6% vs. 15.5%) and major bleeding (65.8% vs. 33.0%)

Study outcomes

The procedural implant success rate in SURPASS was 97.5%.

Key comparisons between the SURPASS cohort (N = 97,185) and the PINNACLE FLX cohort (N = 400), were as follows:

• At time of discharge (or seven days after implantation, whichever was longer), rates of the key safety endpoint — defined as all-cause death, ischemic stroke, systemic embolism, or device or procedure-related events requiring open cardiac surgery or major endovascular intervention — were similar, at 0.5%. This endpoint was used because it matched the one used in PINNACLE FLX.
• At 45 days, rates of all death were 0.8% in SURPASS vs. 0.5% in PINNACLE FLX; rates of ischemic stroke were 0.2% vs. 0.7%, respectively; rates of major bleeding were 3.1% vs. 3.0%, respectively; and freedom from peridevice leak was 83.1% vs. 82.8%, respectively.
• At 1 year, rates of all death were 8.2% in SURPASS vs. 6.6% in PINNACLE FLX; rates of ischemic stroke were 1.2% vs. 2.6%, respectively; and rates of major bleeding were 6.4% vs. 7.9%, respectively.

Comparable safety despite a higher-risk real-world population

“The key safety outcome of major adverse events before hospital discharge occurred at a similar rate of approximately 0.5% in SURPASS and PINNACLE FLX despite the higher risk profile of SURPASS patients,” Dr. Kapadia notes. “This and the other safety outcomes provide good reassurance that the device is being used safely.”

The study authors point out that patient management differed between SURPASS and PINNACLE FLX, likely contributing to the safety results observed in the SURPASS cohort. At discharge, PINNACLE FLX patients were prescribed a direct oral anticoagulant plus aspirin, per study protocol, whereas only about 40% of SURPASS patients received this regimen. Many SURPASS patients were provided an oral anticoagulant alone, and evidence since the PINNACLE FLX trial suggests that this may lead to a lower risk of adverse events through 45 days.

Dr. Kapadia notes that SURPASS, being a registry study, was not specifically designed to evaluate efficacy, as full outcomes data were not available. “Our primary objective was to assess safety in real-world settings, in view of the widespread adoption of the WATCHMAN FLX,” he says. He adds, however, that given the study’s huge dataset, evidence is strong that efficacy outcomes were comparable to those in PINNACLE FLX. “Ongoing randomized controlled trials such as OPTION and CHAMPION-AF will provide further clarity on efficacy,” he notes.

Additional perspectives

“These data from SURPASS leave little doubt that LAA occlusion is a safe and effective strategy for stroke prevention in patients with nonvalvular atrial fibrillation,” says Mohamed Kanj, MD, Associate Director of Electrophysiology Laboratories in Cleveland Clinic’s Department of Cardiovascular Medicine. “The rate of reported stroke was a quarter of what you would expect in this population. The WATCHMAN FLX device gets much of the credit because it has improved the procedural success rate and reduced the rate of adverse outcomes.”

“The results of this latest SURPASS analysis are very encouraging, especially the high implant success rate,” adds Oussama Wazni, MD, MBA, Section Head of Cardiac Electrophysiology at Cleveland Clinic. “This is made possible by the device’s wider range of sizes and the operator’s ability to adjust its placement to obtain the best possible closure.”

The SURPASS analysis was supported by Boston Scientific Corporation, which markets the WATCHMAN FLX.

Image of the WATCHMAN FLX device is courtesy of Boston Scientific.