Watchman Registry: 1-Year Stroke Estimates Reassuringly Low

Patrice Wendling

May 15, 2021

The Watchman left atrial appendage (LAA) closure device (Boston Scientific) is associated with low 1-year stroke rates, despite being used commercially in older, sicker patients than seen in pivotal clinical trials, new data suggest.

Among more than 36,000 patients with atrial fibrillation (AF), the Kaplan-Meier estimated rate of ischemic stroke at 1 year was 1.53% (95% CI, 1.40% - 1.66%).

This represents a 77% relative risk reduction in ischemic stroke with the device than would be expected based on the patients' CHA2DS2-VASc score if left untreated (6.64% vs 1.53%).

The cumulative ischemic stroke rate was 1.40 per 100 person-years (95% CI, 1.27 - 1.53).

"Thromboembolic events at 1 year are infrequent among patients undergoing commercial Watchman implantation, which supports the early-to-mid-term clinical effectiveness as it is currently being utilized in the United States," Matthew J. Price, MD, said at the American College of Cardiology (ACC) 2021 Scientific Session.

The Watchman device was approved in 2015 for the prevention of stroke in high-risk patients with nonvalvular atrial fibrillation (AF) and is touted as an alternative to lifelong oral anticoagulation. The newest iteration, the Watchman FLX, gained approval in 2020.

This study was based on 36,681 patients in the National Cardiovascular Data Registry (NCDR) LAA Occlusion (LAAO) Registry implanted with a Watchman device from January 2016 through December 2018. Participation in the registry is mandated by the U.S. Food and Drug Administration as part of its postmarketing surveillance and is required for Centers for Medicare & Medicaid Services (CMS) reimbursement.

Early procedural outcomes reported at last year's ACC meeting show a higher implant success rate and substantially lower in-hospital complication rate in the real world than that seen in the pivotal PROTECT-AF and PREVAIL trials.

There is a paucity of data, however, regarding longer-term safety and effectiveness of the Watchman device in contemporary practice, noted Price, director of the cardiac catheterization lab at Scripps Clinic, La Jolla, California. The population in the randomized trials leading to the Watchman approval also differs substantially from that indicated in the CMS coverage decision.

CMS covers patients with a CHADS2 score of 2 or greater or a CHA2DS2-VASc score of 3 or greater who are suitable for short-term warfarin but deemed unable to take long-term oral anticoagulation. In contrast, trial participants had lower thromboembolic risk (CHADS2 score ≥ 1 for PROTECT-AF and CHADS2 score ≥ 2 or CHADS2 score ≥ 1 with conditions for PREVAIL) and were eligible for long-term warfarin.

LAAO registry patients were, on average, 76 years old, compared with 71.7 years in PROTECT-AF and 74 years in PREVAIL, and they had a higher mean CHA2DS2-VASc score (4.6 vs 3.4 vs 3.8, respectively). One-quarter had previously had a stroke or transient ischemic attack (29.8% vs 17.7% vs 27.5%) and 69.4% previously had clinically relevant bleeding (trial data not available). Median follow-up was 373 days (interquartile range, 208 to 425 days).

At 1 year, the estimated mortality rate was 8.52%, with 32.6% of cases due to cardiovascular mortality, 60.3% to noncardiovascular death, and 7.1% not specified. The cumulative rate of all-cause mortality was 7.58 per 100 person-years.

The estimated 1-year rate of major bleeding was 6.2% (cumulative rate, 7.08/100 person-years).

"The incidence of 1-year mortality is not infrequent, mostly from noncardiovascular death, and the risk of bleeding, particularly early in the first 6 weeks, is higher than seen in the randomized trials. So these balancing risks need to be taken into account when considering the Watchman device for a patient," Price told | Medscape Cardiology.

Although 93.6% of patients in the registry had at least one follow-up visit after discharge, the percentage of patients with follow-up fell to 78% at 180 days and 71% at 365 days.

There were no differences, however, among patients with and without follow-up in thromboembolic risk (CHA2DS2-VASc, both 4.8) or bleeding risk based on HAS-BLED score (both 3.0) or clinically relevant prior bleeding (69.4% vs 70.2%; P = .39), Price noted. AF classification was also similar (paroxysmal AF, 52.4% vs 52.2%; P = .82).

"This is an impressive response in terms of comparing real-world data to what we have in the studies," panelist and electrophysiologist Jodie Hurwitz, MD, Medical City Hospital, Dallas, Texas, said during a discussion of the results.

Hurwitz asked whether information will be forthcoming regarding the use of warfarin and dual antiplatelet therapy among the registry patients. Price noted that early results reported last year included these data in about 32,000 patients out to 45 days.

"The relatively low stroke events cannot be ascribed to LAAO alone because patients do take a short-term of post-procedure pharmacotherapy," he said. "But certainly, given the risk of the population, the results are reassuring about how we're practicing medicine now in the United States with the Watchman, and using these pharmacotherapies afterwards translates into low thromboembolic event rate."

Price said forthcoming analyses will examine in-hospital complication rates based on hospital volume. "Understanding the relationship between hospital volume, physician experience, and outcomes will be important."

Asked whether the results in these "incredibly sick" patients may be enough to strengthen the soft IIb recommendation for LAAO in clinical guidelines, Price said randomized data in this population are lacking. The randomized ASAP-TOO trial in patients unsuitable for oral anticoagulation was stopped because of low enrollment, although randomized trials comparing the Watchman with novel oral anticoagulants in patients who are good candidates for OAC will help inform guidelines.

"It would be nice to see a consensus paper, so more people can get access," Hurwitz said. "This is very impressive."

Price reported consultant fees/honoraria from Abbott Vascular, Accutus, AstraZeneca, Baylis Medical, Boston Scientific, InnovHeart, Johnson & Johnson, MEDTRONIC, and W.L. Gore; speaker's bureau participation for Abbott Vascular and AstraZeneca; and stock in Indian Wells. Hurwitz reported serving as an officer, director, trustee, or other fiduciary role for Medical City Dallas; having an ownership interest/partnership/principal role with the Heart Hospital Baylor Plano; and serving on Medtronic's speaker's bureauc.

American College of Cardiology (ACC) 2021 Scientific Session.  Abstract 403-11. Presented May 15, 2021.

Follow Patrice Wendling on Twitter: @pwendl. Follow ACC.21 coverage from | Medscape Cardiology on Twitter and Facebook.


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