How The WATCHMAN Device Works

A One-Time Procedure.
A Life-Changing Alternative

"It was the best feeling to know that WATCHMAN was going to watch over me"
Marjorie Giovannoni, WATCHMAN recipient


Consider a permanent solution designed to reduce the risk of stroke

The left atrial appendage closure (LAAC) with the WATCHMAN FLX device offers an innovative minimally-invasive one-time procedure for patients with atrial fibrillation not caused by a heart valve problem (also known as non-valvular AF) who are contraindicated or eligible for oral anticoagulants.

The device is designed to close the left atrial appendage (which is known to be the main source of blood clots in patients with AF), preventing the migration of the blood clots to the brain.



To understand how WATCHMAN FLX works, it helps to know more about the connection between atrial fibrillation and stroke.

Atrial fibrillation, or AF, affects your heart’s ability to pump blood normally. This can cause blood to pool in an area of the heart called the left atrial appendage, or LAA. There, blood cells can stick together and form a clot. When a blood clot escapes from the LAA and travels to another part of the body, it can cut off the blood supply to the brain, causing a stroke.2,3

blood clot in left atrial appendage illustration

In people with AF not caused by a heart valve problem, more than 90% of stroke-causing clots that come from the heart are formed in the LAA.2 That’s why closing off this part of the heart is an effective way to reduce stroke risk.

The WATCHMAN FLX Implant fits right into your LAA. It’s designed to permanently close it off and keep those blood clots from escaping. WATCHMAN FLX is about the size of a coin and made from very light and compact materials commonly used in many other medical implants.

The WATCHMAN FLX Procedure

The WATCHMAN FLX Procedure

WATCHMAN FLX is implanted into your heart in a one-time procedure. It’s a permanent device that doesn’t have to be replaced and can’t be seen outside the body.

To implant WATCHMAN FLX, your doctor makes a small cut in your upper leg and inserts a narrow tube, as done in a standard stent procedure. Your doctor then guides WATCHMAN FLX into the left atrial appendage (LAA) of your heart. The procedure is done under general anesthesia or conscious sedation and takes about an hour. Patients commonly stay in the hospital overnight and leave the next day.

Due to the risk of having a medical procedure, patients should not be considered for WATCHMAN FLX if they are doing well and expect to continue doing well on blood thinners.

WATCHMAN FLX Medical Centers

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Patient and child

After the Procedure

Following the WATCHMAN FLX procedure, your doctor will assess your individual characteristics and conditions, such as bleeding risk, stroke risk, and your preference and will decide which is the best post-implant drug regimen for you to have your LAA permanently closed off. He could prescribe you dual antiplatelet therapy (DAPT), novel oral anticoagulants (NOACs) or vitamin K antagonist (VKA), along with aspirin. During this time, heart tissue will grow over the implant to form a barrier against blood clots. Your doctor will monitor this process by taking pictures of your heart to see when you can stop taking medications. A very small number of patients may need to keep taking blood thinners long term.

WATCHMAN Platform clinical studies

WATCHMAN Platform clinical studies

The WATCHMAN Platform is the only one proven to safely and effectively reduce the risk of stroke and long-term risk of bleeding associated with use in patients with non-valvular AF.

More than 100,000 WATCHMAN and WATCHMAN FLX procedures have been performed worldwide. And with over 10 years of clinical studies behind it, the WATCHMAN LAAC platform has a proven safety record with high rate of patients successfully implanted and very low adverse events.4

As with any medical procedure, there are risks involved with WATCHMAN FLX. See the Important Safety Information below for a list of possible complications, and ask your cardiologist about the risks and benefits of WATCHMAN FLX.



Get a quick guide on WATCHMAN FLX that you can share with your doctor or loved one.

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If you have AF not caused by a heart valve problem and you need an alternative to blood thinners, WATCHMAN FLX may be right for you.

Next: Why Choose WATCHMAN FLX

WATCHMAN FLX is for people with atrial fibrillation not caused by a heart valve problem who need an alternative to oral anticoagulants. This website is intended to provide patients and caregivers with some information about the WATCHMAN FLX Implant. It may help prepare you for talking to your doctor about your options for reducing stroke risk.

Important Safety Information

The WATCHMAN and WATCHMAN FLX Devices are permanent implants designed to close the left atrial appendage in the heart in an effort to reduce the risk of stroke.
With all medical procedures there are risks associated with the implant procedure and the use of the device. The risks include but are not limited to accidental heart puncture, air embolism, allergic reaction, anemia, anesthesia risks, arrhythmias, AV (Arteriovenous) fistula, bleeding or throat pain from the TEE (Trans Esophageal Echo) probe, blood clot or air bubbles in the lungs or other organs, bruising at the catheter insertion site, clot formation on the WATCHMAN™ and WATCHMAN FLX Closure Devices, cranial bleed, excessive bleeding, gastrointestinal bleeding, groin puncture bleed, hypotension, infection/pneumonia, pneumothorax, pulmonary edema, pulmonary vein obstruction, renal failure, stroke, thrombosis and transient ischemic attack. In rare cases death can occur.
Be sure to talk with your doctor so that you thoroughly understand all of the risks and benefits associated with the implantation of the WATCHMAN and WATCHMAN FLX Devices.

CAUTION: The law restricts these devices to sale by or on the order of a physician. Indications, contraindications, warnings and instructions for use can be found in the product labeling supplied with each device. Information for the use only in countries with applicable health authority product registrations.

Content of this website is for Information Purposes only and not meant for product promotion or medical diagnostic. This information does not constitute medical or legal advice, and Boston Scientific makes no representation or warranty regarding this information or its completeness, accuracy or timeliness. 

Accordingly, Boston Scientific strongly recommends that you consult with your physician on all matters pertaining to your health or to address any questions.


  1. Holmes DR Jr, Kar S, Price MJ, et al. J Am Coll Cardiol. 2014;64(1):1-12. 
  2. Blackshear JL, Odell JA. Appendage obliteration to reduce stroke in cardiac surgical patients with atrial fibrillation. Ann Thorac Surg. 1996;61:755-759. 
  3. National Stroke Association. Making the Afib-Stroke Connection. Published 2012. Accessed September 1, 2016. 
  4. Holmes DR Jr, Doshi SK, Kar S, et al. J Am Coll Cardiol. 2015;65(24):2614-2623.