Blog Description

Product Review: Boston Scientific WATCHMAN FLX

Healthcare | May, 2021

Millions of people around the world are living with atrial fibrillation (AF), which starts as an irregular or rapid heart rhythm that gradually becomes stronger and more constant. Many people do not even know they are living with the condition as the symptoms can be easily overlooked. However, some people dealing with AF experience symptoms such as extreme fatigue, feeling faint, chest pain, shortness of breath, and heart palpitations. The life-threatening condition results from thrombus formation, whose prevalence increases with age. Anatomically, the left atrial appendage (LAA) is the major source of blood clots in patients with non-valvular AF. Although oral blood-thinning medications are the standard treatments for AF, several challenges limit its use such as non-compliance, bleeding issues, fall risk, frequent prothrombin time monitoring, etc. The LAA closure device introduced by Boston Scientific, WATCHMAN FLX is a permanent implantable device that provides prevention against strokes in high-risk patients with non-valvular atrial fibrillation. The WATCHMAN Implant is a one-time procedure that allows the patients to stop their anticoagulation medicines after 45 days. Watchman FLX is the newest generation of LAA closure device with more advanced features compared to the previous generation WATCHMAN, which has been commercially available for use since 2009. 


Available in five sizes for Ostia measuring from 15 mm to 32 mm in width, the device can be implanted in small as well as large LAA. The device consists of a self-expanding nitinol frame structure with 12 “J” shaped fixation anchors and permeable polyester fabric. Compared to the 10-strut frame in the previous version, the Watchman FLX device provides 80% more contact points at the LAA ostium with an 18-strut frame. The nitinol frame radially expands to maintain a proper position in the LAA. The device is pre-loaded in the delivery system and comes in two curve configurations—single, double, for different LAA orientations and anchors in two rows create a proximal and distal line to help the device stabilization. The fluoroscopic market at the atraumatic closed distal end enhances the procedural visibility. 



Allowing the flexibility of intra-LAA placement, the device prevents contact with the left atrial wall and reduces risks of device erosion along with minimizing interference with the left upper pulmonary vein and mitral valve. Although the device facilitates a greater compression ranging from 10-27%, it works best when not over-compressed since the frame has stability at low compression due to its closed distal end. Just like the previous generation device, the new WATCHMAN FLX can be partially recaptured or repositioned either proximally or advanced distally several times before using the “ball technique”, which enables the right device placement. The device even allows full recapture at every stage of the procedure before the final device release. 


How is WATCHMAN FLX implanted?

The implantable WATCHMAN device looks like a tiny parachute made from flexible mesh and spring wires. The doctor inserts the device through a catheter (flexible tube) into the patient’s vein in the groin area and advances it to the upper right chamber of the heart. Making a small hole between the two upper chambers, the catheter reaches into a patient’s LAA. The doctor then releases the WATCHMAN FLX device into the left atrial appendage (LAA) where it opens up like an umbrella to prevent harmful blood clots from entering the bloodstream and prevent possible stroke. The round design of the device allows optimal placement of the device and assures long-term stability. Once the device is positioned appropriately, a thin layer of tissue grows within 45 days, which further prevents blood clots from entering the bloodstream. The broader size range of the newest version of the implant helps to treat more patients safely and effectively. 


Advantages of using Boston Scientific Watchman FLX


  • Traditional open-chest procedure requires sternotomy (large incision in the chest) and heart-lung bypass machine to take over the functions of the heart and lungs during the procedures whereas minimally invasive, catheter-based intervention with Watchman FLX can be performed while the patient’s heart is beating. Therefore, the Watchman FLX device reduces the risk of complications, recovery time, medical costs, and offers long-term stability. 
  • The insertion of the special catheter which carries the Watchman device into the large blood vessel is supported with advanced imaging technology, which reduces the risk of errors and aid in optimal positioning of the device. 
  • The one-time intervention takes about an hour, right from choosing the appropriate sized device to releasing it into the heart. 
  • The Watchman FLX device is FDA-approved for its use in the LAA procedure. 
  • The implantation of the device can be performed using monitored anesthesia care. 
  • The person can be discharged within 24 hours of the procedure with a catheter-based procedure. 
  • The device frees people with AFib from the daily challenges of taking blood-thinning medications, which becomes of utmost significance for people who are not eligible for long-term blood thinner intake.


 Who should not use the WATCHMAN FLX device?

The WATCHMAN FLX device should not be implanted in patients who

  • Currently have blood clots in the heart
  • Undergone surgical repair of the atrial septum 
  • Have a too large or small LAA to fit the device
  • Cannot take blood-thinning medications
  • Have sensitivity to nitinol or any other material used in the device



Just like all procedures, the implantation of WATCHMAN FLX carries some degree of risk. For instance, the blood clot or air can get in the catheter, which is to be further injected into the heart. If a blood clot or air reaches the brain, stroke is inevitable. However, physicians can minimize these risks by taking the precautionary step of flushing out the catheter. Another possible complication during the LAA procedure can be left atrial appendage rupture, caused by some pressure while the device is implanted. This complication might require an emergency heart surgery otherwise the patient could lose his life. Due to a higher-than-anticipated embolization rate of 3.8%, Boston Scientific had to withdraw WATCHMAN FLX. So, the manufacturer is planning for more design enhancements in the device maintaining key benefits of the latest generation WATCHMAN FLX such as enhanced ostial sea, distal redeployment, enhanced stability, more forgiving placement at the ostium, etc. 


Other Devices for LAA Occlusion


St. Jude Medical’s Amplatzer Amulet LAA 

Another potential device designed for the left atrial appendage aims to reduce the risk of stroke arising from Atrial Fibrillation. The device works by sealing off the opening of LAA to prevent the entry of clots into the heart, which could further mix into the bloodstream, reach the brain, and cause a stroke. The Amplatzer Amulet LAA Occluder is the second-generation device, designed with a longer lobe, wider waist than, recessed screws, and more stabilizing wires than Amplatzer Cardiac Plug, the previous version of St. Jude Medical LAA device. The new-gen device facilitates easier and more stable placements, which leads to shorter procedure time along with reducing the thrombus formation on the atrial side of the device. Unlike ACP that required manual loading, the Amulet comes with a preloaded delivery cable for easy setup.


Available in eight sizes (16, 18, 20, 22, 25, 28, 31, and 34 mm) to accommodate a wider range of varying patient anatomies (up to 32 mm), the Amplatzer Amulet LAA Occluder stands as a strong competitor for Watchmen FXL that provides only five different sizes. Also, the St. Jude LAA occluder is CE mark approved and hit in Europe while Watchman did not receive much success in the region.


Appriva Medical’s Percutaneous Left Atrial Appendage Transcatheter Occlusion (PLAATO)

PLAATO device was the first LAA device that was implanted in humans in 2001. Consisting of a self-expanding nitinol cage ranging in diameter 15 to 32 mm, three anchors on each strut, the device was covered with non-thrombogenic polytetrafluoroethylene membrane to exclude blood flow into the remaining LAA. Despite providing promising results, the device was withdrawn from the market for commercial reasons after few years.


SentreHEART Inc. Lariat

The FDA-approved catheter-based Lariat LAA closure is a complex hybrid procedure requires both epicardial as well as endocardial approach. The device is not specifically approved for stroke prevention with AF but for knot tying during surgical applications. During the LARIAT procedures, two catheters are guided into the heart to seal the LAA with a pre-tied suture loop via LARIAT Suture Delivery Device. Gradually, the appendage turns into scar tissue and thus permanently prevents the blood clots to enter the heart. 



The next generation WATCHMAN FLX is the first closure device that can be redeployed after partial or full re-capture. The WATCHMAN implant has remained one of the leading devices for percutaneous left atrial globally and now the new one is taking in-charge due to its higher effectiveness. The LAA closure procedure is in its infacy, and several issues are yet to be addressed.

According to TechSci research report on “Global Interventional Cardiology Devices Market By Product Type (Angioplasty Balloons, Angioplasty Stents, Structural Heart Devices, Catheters, Plaque Modification Devices, Hemodynamic Flow Alteration Devices, Others) By End User (Hospitals & Clinics, Ambulatory Surgery Centers, Others) By Region, Competition Forecast & Opportunities, 2026”, global interventional cardiology devices market is expected to grow at a formidable CAGR owing to factors like increasing incidences of cardiovascular problems and technological advancements in medical devices introduced in this domain.

According to another TechSci research report on “United States Cardiology Surgical and Interventional Devices Market By Product Type (Cardiovascular Surgical Devices, Interventional Devices), By Surgical Approach (Open-Heart Surgery, Off-Pump Heart Surgery, Minimally Invasive Heart Surgery), By Type of Cardiac Surgery (Coronary Artery Bypass Grafting (CABG), Transmyocardial Laser Revascularization (TMR), Heart Valve Repair or Replacement, Heart Transplant, Arrhythmia Treatment, Others), By End User (Hospitals & Clinics, Ambulatory Surgical Centers, Others), By Region, Forecast & Opportunities, 2025”, United States cardiology surgical and interventional devices market is expected to grow at a significant rate due to growing geriatric population and rising incidences of coronary artery diseases. 


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