An interventional study of WATCHMAN device in Atrial Fibrillation, Stroke, Ischemic and Systemic Embolism, sponsored by Hamilton Health Sciences Corporation. Recruiting at 150 sites in 12 countries. Open to participants aged 18 Years and older. Per ClinicalTrials.gov, last updated 2026-09-18.
Sponsored by Hamilton Health Sciences Corporation · Not applicable, Interventional, and Treatment
LAAOS-4 aims to determine if catheter-based endovascular left atrial appendage occlusion prevents ischemic stroke or systemic embolism in participants with atrial fibrillation, who remain at high risk of stroke, despite receiving ongoing treatment with oral anticoagulation.
LAAOS-4 is a multicentre, prospective, open-label, randomized controlled trial with blinded assessment of endpoints (PROBE) to determine if catheter-based endovascular left atrial appendage occlusion prevents ischemic stroke or systemic embolism in participants with atrial fibrillation, who remain at high risk of stroke, despite receiving ongoing treatment with oral anticoagulation.
4,009 studies on the registry are indexed under Atrial Fibrillation; 961 are open to participants now.
This study's planned enrollment of 4,000 is above the median of 150 across 2,476 interventional studies indexed under Atrial Fibrillation.
Browse Atrial Fibrillation studies →Hamilton Health Sciences Corporation is the lead sponsor of 242 studies on the registry; 38 are open to participants now.
Counted across the registry records on this site, refreshed daily.
Go through the criteria one by one — yes, no or not sure — and take the list to your doctor or the study team. Kept in this browser only.
Exclusion Criteria:
Underlined terms in the criteria open these too. Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Able to become pregnant: from the first period until menopause, unless permanently unable to through surgery (removal of the womb, or of both ovaries or both fallopian tubes).
Criteria for people of childbearing potential usually ask for a negative pregnancy test and for contraception during the study and for a time after it.
Ways of preventing pregnancy. “Highly effective” methods fail less than 1% of the time a year when used correctly — for example an IUD or an implant.
Criteria usually say which methods count and how long to keep using them after the last dose, sometimes for male participants too. Some studies accept a partner’s vasectomy if it was confirmed successful and that person is the participant’s only sexual partner.
Before you join, the study team explains what taking part involves — its purpose, what happens, the risks and possible benefits — and answers your questions, so you can decide freely. Consent is usually recorded on a form (the informed consent form, ICF) signed by you or, where the law allows, by someone legally authorised to decide for you.
You can keep asking questions during the study, you are told of new information that matters, and you can choose to leave at any time.
Childbearing potential
Able to become pregnant: from the first period until menopause, unless permanently unable to through surgery (removal of the womb, or of both ovaries or both fallopian tubes).
Criteria for people of childbearing potential usually ask for a negative pregnancy test and for contraception during the study and for a time after it.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Contraception
Ways of preventing pregnancy. “Highly effective” methods fail less than 1% of the time a year when used correctly — for example an IUD or an implant.
Criteria usually say which methods count and how long to keep using them after the last dose, sometimes for male participants too. Some studies accept a partner’s vasectomy if it was confirmed successful and that person is the participant’s only sexual partner.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Informed consent
Before you join, the study team explains what taking part involves — its purpose, what happens, the risks and possible benefits — and answers your questions, so you can decide freely. Consent is usually recorded on a form (the informed consent form, ICF) signed by you or, where the law allows, by someone legally authorised to decide for you.
You can keep asking questions during the study, you are told of new information that matters, and you can choose to leave at any time.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Participants will undergo endovascular left atrial appendage occlusion with the WATCHMAN device
Device: WATCHMAN device
Participants will receive local, standard medical care
Participants will undergo endovascular left atrial appendage occlusion with the WATCHMAN device
Ischemic stroke or systemic embolism
The primary efficacy variable is the time from randomization to first occurrence of any of the components of the composite outcome (adjudicated) over the duration of follow-up, including: * Ischemic stroke (Strokes of undetermined etiology will be treated as ischemic stroke) * Systemic embolism
Time frame: The study duration is event-driven. The primary analysis will be performed through study completion, once 265 primary efficacy endpoint events have occurred (an estimated average follow-up of 4 years).
All-cause stroke or systemic embolism
Secondary efficacy outcomes will be evaluated in a hierarchical fashion only when the primary outcome meets statistical significance in the specified order: Time from randomization to first occurrence of all-cause stroke or systemic embolism
Time frame: Will be evaluated once primary outcome meets statistical significance. The primary analysis will be performed through study completion, once 265 primary efficacy endpoint events have occurred (an estimated average follow-up of 4 years).
All-cause stroke, systemic embolism, or transient ischemic attack (TIA)
Time from randomization to first occurrence of all-cause stroke, systemic embolism or transient ischemic attack (TIA)
Time frame: Will be evaluated once primary outcome meets statistical significance. The primary analysis will be performed through study completion, once 265 primary efficacy endpoint events have occurred (an estimated average follow-up of 4 years).
Montreal Cognitive Assessment (MoCA) Score
Proportion of participants with a decrease of two or more points on the MoCA score at either year 2 or end of study
Time frame: Will be evaluated once primary outcome meets statistical significance. The primary analysis will be performed through study completion, once 265 primary efficacy endpoint events have occurred (an estimated average follow-up of 4 years).
New disabling ischemic strokes
Time from randomization to first occurrence of disabling ischemic strokes with modified Rankin Score (mRS) \>2, measured at 90 days post-stroke
Time frame: Will be evaluated once primary outcome meets statistical significance. The primary analysis will be performed through study completion, once 265 primary efficacy endpoint events have occurred (an estimated average follow-up of 4 years).
Cardiovascular mortality
Time from randomization to cardiovascular mortality
Time frame: Will be evaluated once primary outcome meets statistical significance. The primary analysis will be performed through study completion, once 265 primary efficacy endpoint events have occurred (an estimated average follow-up of 4 years).
All-cause mortality
Time from randomization to all-cause mortality
Time frame: Will be evaluated once primary outcome meets statistical significance. The primary analysis will be performed through study completion, once 265 primary efficacy endpoint events have occurred (an estimated average follow-up of 4 years).
Non-procedural Major Bleeding
Proportion of participants with non-procedural Major Bleeding (International Society on Thrombosis and Haemostasis (ISTH) definition; excluding WATCHMAN-related bleeding within 14 days of implant)
Time frame: Will be evaluated once primary outcome meets statistical significance. The primary analysis will be performed through study completion, once 265 primary efficacy endpoint events have occurred (an estimated average follow-up of 4 years).
Hospitalization for any cause
Time from randomization to first occurrence of hospitalization for any cause
Time frame: Will be evaluated once primary outcome meets statistical significance. The primary analysis will be performed through study completion, once 265 primary efficacy endpoint events have occurred (an estimated average follow-up of 4 years).
Heart failure hospitalization or emergency department/clinic visit for intensification of heart failure related therapy
Time from randomization to first occurrence of heart failure hospitalization or emergency department/clinic visit for intensification of heart failure related therapy
Time frame: Will be evaluated once primary outcome meets statistical significance. The primary analysis will be performed through study completion, once 265 primary efficacy endpoint events have occurred (an estimated average follow-up of 4 years).
Myocardial Infarction
Time from randomization to first occurrence of Myocardial Infarction (4th Universal definition)
Time frame: Will be evaluated once primary outcome meets statistical significance. The primary analysis will be performed through study completion, once 265 primary efficacy endpoint events have occurred (an estimated average follow-up of 4 years).
Device and procedural-related outcomes: Device-related thrombus
Proportion of participants with device-related thrombus (thrombus formed on the surface of the WATCHMAN device)
Time frame: Will be evaluated once primary outcome meets statistical significance. The primary analysis will be performed through study completion, once 265 primary efficacy endpoint events have occurred (an estimated average follow-up of 4 years).
Device and procedural-related outcomes: Incomplete left atrial appendage (LAA) closure
Proportion of participants with incomplete LAA closure
Time frame: Will be evaluated once primary outcome meets statistical significance. The primary analysis will be performed through study completion, once 265 primary efficacy endpoint events have occurred (an estimated average follow-up of 4 years).
Device and procedural-related outcomes: Peri-procedural major bleeding
Proportion of participants with peri-procedural major bleeding (ISTH definition; within 14 days following the procedure)
Time frame: Will be evaluated once primary outcome meets statistical significance. The primary analysis will be performed through study completion, once 265 primary efficacy endpoint events have occurred (an estimated average follow-up of 4 years).
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Showing the first 100 of 150 sites across 12 countries. Choose a country and city above to see the rest.
Plan to share: No
Started Nov 2023 (actual). Primary completion is estimated for Sep 2029, 69 months after the start.
Of 796 non-industry interventional studies with no phase under Atrial Fibrillation, half reached primary completion within 40 months of starting (the median), counting those still running; a quarter within 21 and three quarters within 59. This study's planned 69 months is above that.
Counting every sponsor, half of 1,051 studies reached it within 33 months; a quarter within 18 and three quarters within 54.
How these figures are worked out, and which studies are left out of them.
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