Could a tiny implant replace daily blood thinners for AFib patients?

NCT ID NCT04394546

Disease control Sponsor: Boston Scientific Corporation Source: ClinicalTrials.gov ↗

First seen Jun 27, 2026 · Last updated Sep 11, 2026 · Updated 5 times

Summary

This large study is testing whether a device called WATCHMAN FLX, which closes off a small pouch in the heart, can be a safe and effective alternative to daily blood thinners (NOACs) for preventing strokes in people with non-valvular atrial fibrillation. The trial involves 3,000 participants and compares the device against standard medication. The goal is to see if the device can reduce bleeding complications while still protecting against strokes.

What this could mean

Our plain-language read of the trial. This is informational only, not medical advice or a prediction.

Active substance: WATCHMAN FLX Left Atrial Appendage Closure Device
What this could lead to: If successful, this could offer a long-term alternative to daily blood thinners for preventing strokes in people with atrial fibrillation, reducing bleeding risks.
What could go wrong: The device requires an invasive implantation procedure and may not be as effective as blood thinners for preventing all strokes. Bleeding risks from the procedure itself are also a concern.

This is an AI summary of the original study and may miss details. Read our disclaimer.

Study facts

What this study's own registry entry says, in plain language.

Phase

Not a phased trial

Phase numbers describe drug development. The registry uses this when they do not apply, as it does for trials of devices, procedures or behaviour changes, and for observational studies.

Participants

3,000 people

The number who actually took part.

Started

Oct 2020

Expected to finish

Dec 2027

An estimate. End dates often move.

Lead sponsor

A company

The lead sponsor is a pharmaceutical, biotech, or medical-device company.

Who can take part

This study's own entry requirements. Only the study team can say for certain whether you qualify.

Ages

18 years and older

Sex

Anyone

Healthy volunteers

Not accepted

This study is not open to healthy volunteers. The entry requirements below say who it is open to.

Show the full entry requirements

Copied word for word from the study's registry entry, so the wording is the study team's rather than ours.

Inclusion Criteria: * The subject is of legal age to participate in the study per the laws of their respective geography * The subject has documented non-valvular atrial fibrillation (i.e., atrial fibrillation in the absence of moderate or greater mitral stenosis or a mechanical heart valve) * The subject has a calculated CHA2DS2-VASc (congestive heart failure, hypertension, age ≥ 75 years, diabetes mellitus, stroke or transient ischemic attack (TIA), vascular disease, age 65 to 74 years, sex category) score of 2 or greater for men and 3 or greater for women * The subject is deemed to be suitable for the protocol-defined pharmacologic regimens in both the test and control arms * The subject or legal representative is able to understand and willing to provide written informed consent to participate in the trial * The subject is able and willing to return for required follow-up visits and examinations Exclusion Criteria: * Subjects who are currently enrolled in another investigational study, except when the subject is participating in a mandatory governmental registry, or a purely observational registry with no associated treatments * The subject requires long-term anticoagulation therapy for reasons other than AF-related stroke risk reduction, for example due to an underlying hypercoagulable state (i.e., even if the device is implanted, the subjects would not be eligible to discontinue OAC due to other medical conditions requiring chronic OAC therapy) * The subject is contraindicated or allergic to oral anticoagulation medication and/or aspirin * The subject is indicated for chronic P2Y12 platelet inhibitor therapy * The subject had or is planning to have any cardiac or non-cardiac intervention or surgical procedure within 30 days prior to or 60 days after implant (including, but not limited to: cardioversion, percutaneous coronary intervention (PCI), cardiac ablation, cataract surgery, etc.) * The subject had a prior stroke (of any cause, whether ischemic or hemorrhagic) or transient ischemic attack (TIA) within the 30 days prior to enrollment * The subject had a prior major bleeding event per ISTH definition within the 30 days prior to randomization. Lack of resolution of related clinical sequelae or planned and pending interventions to resolve bleeding/bleeding source, are a further exclusion regardless of timing of the bleeding event * The subject has an active bleed * The subject has a reversible cause of AF or transient AF * The subject is absent of a left atrial appendage (LAA) or the LAA is surgically ligated * The subject has had a myocardial infarction (MI) documented in the clinical record as either a non-ST elevation MI (NSTEMI) or as an ST-elevation MI (STEMI), with or without intervention, within 30 days prior to enrollment * The subject has a history of atrial septal repair or has an atrial septal device (ASD)/patent foramen ovale (PFO) device * The subject has an implanted mechanical valve prosthesis in any position * The subject has a known contraindication to percutaneous catheterization procedure * The subject has a known contraindication to transesophageal echo (TEE) * The subject has a cardiac tumor * The subject has signs/symptoms of acute or chronic pericarditis. * The subject has an active infection * There is evidence of tamponade physiology * The subject has New York Heart Association Class IV Congestive Heart Failure at the time of enrollment * The subject is of childbearing potential and is, or plans to become, pregnant during the time of the study (method of assessment upon study physician's discretion) * The subject has a documented life expectancy of less than 3 years Transthoracic Echo Exclusion Criteria: * The subject has left ventricular ejection fraction ( LVEF) \< 30% * The subject has an existing pericardial effusion with a circumferential echo-free space \> 5mm * The subject has a high-risk PFO with an atrial septal aneurysm excursion \> 15mm or length \> 15mm * The subject has significant mitral valve (MV) stenosis (i.e., MV area \<1.5 cm2)

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Conditions

The condition(s) this trial relates to.

atrial fibrillation Hemorrhage hemorrhagic disease stroke disorder prevention target

As listed by the trial registrant

The condition terms exactly as the trial's registrant entered them.

Atrial fibrillation Bleeding Stroke

Contacts and locations

Locations

Aarhus University Hospital

Aarhus, 8200, Denmark
AdventHealth Orlando

Orlando, Florida, 32803, United States
Advocate Christ Medical Center

Oak Lawn, Illinois, 60453, United States
Arizona Arrhythmia Research Center

Phoenix, Arizona, 85016, United States
Arrythmia Research Group

Jonesboro, Arkansas, 72401, United States
Aurora St. Luke's Medical Center

Milwaukee, Wisconsin, 52315, United States
Azienda Ospedaliera Careggi

Florence, Italy
Baptist Hospital of Miami

Miami, Florida, 33176, United States
Bay Area Cardiology Associates, P.A.

Brandon, Florida, 33511, United States
Bergan Cardiology

Omaha, Nebraska, 68124, United States
Billings Clinic

Billings, Montana, 59101, United States
Brigham and Women's Hospital

Boston, Massachusetts, 02115, United States
Broward General Medical Center

Fort Lauderdale, Florida, 33316, United States
CHI Franciscan Health System

Tacoma, Washington, 98405, United States
CHU Grenoble-Hopital Michallon

Grenoble, 38043, France
CHU de Charleroi

Charleroi, Belgium
Cardiologicum Hamburg Praxis Wandsbek

Hamburg, Germany
Catholic Medical Center

Manchester, New Hampshire, 03102, United States
Centennial Medical Center

Nashville, Tennessee, 37203, United States
Centracare Heart and Vascular Center

Saint Cloud, Minnesota, 56303, United States
Charite, Campus Benjamin Franklin

Berlin, Germany
Charlton Memorial

Fall River, Massachusetts, 02720, United States
Chiba University Hospital

Chiba, Chiba, Japan
Christiana Hospital

Newark, Delaware, 19718, United States
Christus Trinity Mother Frances Health System

Tyler, Texas, 75701, United States
Cleveland Clinic Foundation

Cleveland, Ohio, 44195, United States
Colorado Springs Cardiologist, P.C.

Colorado Springs, Colorado, 80923, United States
Columbia University Medical Center

New York, New York, 10032, United States
Community Hospital

Munster, Indiana, 46321, United States
Dartmouth Hitchcock Medical Center

Lebanon, New Hampshire, 03756, United States
Eisenhower Medical Center

Rancho Mirage, California, 92270, United States
El Camino Hospital

Mountain View, California, 94040, United States
Elisabeth Krankenhaus Essen

Essen, Germany
Emory University Hospital

Atlanta, Georgia, 30322, United States
Englewood Hospital and Medical Center

Englewood, New Jersey, 07631, United States
Erlanger Medical Center

Chattanooga, Tennessee, 37403, United States
Fondazione Toscana Gabriele Monasterio

Pisa, PI, 56126, Italy
Franciscan Health Indianapolis

Indianapolis, Indiana, 46237, United States
Glenfield Hospital

Leicester, United Kingdom
Grandview Medical Center

Birmingham, Alabama, 35243, United States
HealthEast St. Joseph's Hospital

Saint Paul, Minnesota, 55102, United States
Heart Hospital of Austin

Austin, Texas, 78756, United States
Herzzentrum Dresden GmbH

Dresden, Germany
Hopital Cardiologique de Lyon

Bron, France
Hospital Clinico Salamanca

Salamanca, Spain
Hospital de Leon

León, 24071, Spain
Hospital de la Pitie-Salpetriere

Paris, 75151, France
Hospital Álvaro Cunqueiro

Vigo, Pontevedra, Spain
Inova Fairfax Hospital

Falls Church, Virginia, 22042, United States
Institut universitaire de Cardiologie et de Pneumologie de Quebec

Québec, Canada
Instituto Clinico Humanitas

Rozzano, Italy
Iwate Medical University Hospital

Shiwa-gun, Iwate, 028-3695, Japan
John Radcliffe Hospital

Oxford, United Kingdom
Kaleida Health

Buffalo, New York, 14203, United States
Kettering Medical Center

Kettering, Ohio, 45429, United States
King Fahed Medical City- Prince Salman Cardiac Center

Riyadh, Saudi Arabia
Klinikum der Ludwig-Maximilians-Universitat

München, Germany
Kokura Memorial Hospital

Kitakyushu-shi, Fukuoka, 802-8555, Japan
Kurashiki Central Hospital

Okayama, Japan
Lahey Clinic Hospital

Burlington, Massachusetts, 01805, United States
Lakeland Regional Medical Center

Lakeland, Florida, 33805, United States
Legacy Emanuel Hospital & Health Center

Portland, Oregon, 97227, United States
Lexington Medical Center

West Columbia, South Carolina, 29169, United States
Los Robles Hospital and Medical Center

Los Angeles, California, 91360, United States
Manatee Memorial Hospital

Bradenton, Florida, 34205, United States
Marin General Hospital

Greenbrae, California, 94904, United States
Massachusetts General Hospital

Boston, Massachusetts, 02114, United States
Mayo Clinic Foundation

Rochester, Minnesota, 55905, United States
Medical University of South Carolina

Columbia, South Carolina, 29204, United States
Memorial Health University Medical Center

Savannah, Georgia, 31404, United States
Memorial Hermann Memorial City Medical Center

Houston, Texas, 77024, United States
Mercy General Hospital

Sacramento, California, 95819, United States
Mercy Hospital

Coon Rapids, Minnesota, 55433, United States
Mercy Hospital Medical Center

Des Moines, Iowa, 50314, United States
Methodist Le Bonheur Healthcare

Germantown, Tennessee, 38138, United States
Methodist Texsan Hospital

San Antonio, Texas, 78201-2009, United States
Mitsui Memorial Hospital

Chiyoda-ku, Tokyo, Japan
Monash Medical Centre

Clayton, Victoria, 3168, Australia
Monongalia General Hospital

Morgantown, West Virginia, 26505, United States
Mount Sinai Medical Center

New York, New York, 10029, United States
North Mississippi Medical Center

Tupelo, Mississippi, 38801, United States
Northwestern Memorial Hospital

Chicago, Illinois, 60611, United States
Norton Hospital

Louisville, Kentucky, 40202, United States
Novant Health Presbyterian Medical Center

Charlotte, North Carolina, 28204, United States
OhioHealth Research and Innovation Institute-Riverside Methodist Hospital

Columbus, Ohio, 43214, United States
Onze Lieve Vrouw Ziekenhuis

Aalst, 9300, Belgium
Ospedale Degli Infermi

Rivoli, 10098, Italy
PIMA Heart and Vascular

Tucson, Arizona, 85704, United States
PeaceHealth Southwest Medical

Vancouver, Washington, 98668, United States
Phoenix Cardiovascular Research Group

Phoenix, Arizona, 85018, United States
Piedmont Hospital

Atlanta, Georgia, 30309, United States
Pinnacle Health at Harrisburg Hospital

Harrisburg, Pennsylvania, 17101, United States
Poznan University of Medical Sciences

Długa, Poznań, Poland
Providence Regional Medical Center Everett

Everett, Washington, 98201, United States
Rochester General Hospital

Rochester, New York, 14621, United States
Royal Sussex County Hospital

Brighton, United Kingdom
SANA Kliniken Oberfranken Coburg GmbH

Coburg, Germany
Santa Barbara Cottage Hospital

Santa Barbara, California, 93105, United States
Scottsdale Healthcare - Shea

Scottsdale, Arizona, 85258, United States
Scripps Memorial Hospital

La Jolla, California, 92037, United States
Shaare Zedek Medical Center

Jerusalem, Israel
Sharp Chula Vista Medical Center

Chula Vista, California, 91911, United States
Sheba Medical Center

Ramat Gan, Israel
Shonan Kamakura General Hospital

Okamoto, Japan
Sparrow Health System - Sparrow Hospital

Lansing, Michigan, 48912, United States
St. Antonius Ziekenhuis

Nieuwegein, Netherlands
St. Francis Hospital

Roslyn, New York, 11576, United States
St. John's Health Center

Santa Monica, California, 90404, United States
St. John's Hospital

Springfield, Illinois, 62701, United States
St. Katharinen Krankenhaus

Frankfurt, 60389, Germany
St. Luke's Hospital of Kansas City

Kansas City, Missouri, 64111, United States
St. Vincent's Hospital-Sydney

Darlinghurst, New South Wales, Australia
St. Vincent's Medical Center

Jacksonville, Florida, 32204, United States
St.Johann Nepomuk Katholisches Hospitalvereinigung Thüringen GmbH

Erfurt, Germany
Sunnybrook Health Sciences Centre

Toronto, Ontario, Canada
Swedish Medical Center

Seattle, Washington, 98122, United States
Tallahassee Memorial Hospital

Tallahassee, Florida, 32308, United States
Texas Cardiac Arrhythmia Research

Austin, Texas, 78705, United States
The Heart Hospital Baylor Plano

Plano, Texas, 75093, United States
The Nebraska Medical Center

Omaha, Nebraska, 68198, United States
The Toledo Hospital

Toledo, Ohio, 43606, United States
Toho University Ohashi Medical Center

Tokyo, Japan
Toyama University Hospital

Toyama, Japan
Toyohashi Heart Center

Toyohashi, Japan
Trident Medical Center

Charleston, South Carolina, 29406, United States
Universitaetsklinikum Schleswig-Holstein

Lübeck, Germany
University Hospital Zurich

Zurich, 8091, Switzerland
University Hospitals of Cleveland

Cleveland, Ohio, 44106, United States
University of Alabama at Birmingham

Birmingham, Alabama, 35294-6830, United States
University of Iowa Hospitals and Clinics

Iowa City, Iowa, 52242, United States
University of Kansas Hospital

Kansas City, Kansas, 66160, United States
University of Massachusetts Memorial Medical Center

Worcester, Massachusetts, 01655, United States
University of Pittsburgh Medical Center

Pittsburgh, Pennsylvania, 15213, United States
University of Tsukuba Hospital

Tsukuba, Japan
Vanderbilt University Medical Center

Nashville, Tennessee, 37232-7235, United States
Virginia Commonwealth University Health System

Richmond, Virginia, 23219, United States
Washington Hospital Center

Washington D.C., District of Columbia, 20010, United States
Westmead Hospital

Bella Vista, Australia
William Beaumont Hospital

Royal Oak, Michigan, 48073, United States
Yale University School of Medicine

New Haven, Connecticut, 06473, United States
York Hospital

York, Pennsylvania, 17403, United States

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