The Amulet device is a small, self-expanding implant placed inside the heart to prevent strokes in people with atrial fibrillation. Its full name is the Amplatzer Amulet Left Atrial Appendage Occluder, and it works by permanently sealing off a small pouch in the heart where dangerous blood clots tend to form. The FDA approved it as an alternative for people who can’t safely take long-term blood thinners.
Why the Left Atrial Appendage Matters
Atrial fibrillation, often called AFib, causes the upper chambers of the heart to beat irregularly. When blood doesn’t flow smoothly through the heart, it can pool and form clots. The left atrial appendage, a small finger-shaped sac attached to the left upper chamber, is where the majority of these clots originate. If a clot breaks free, it can travel to the brain and cause a stroke.
For most AFib patients, blood thinners like warfarin reduce this risk effectively. But some people have conditions that make long-term blood thinners dangerous: a history of serious bleeding, frequent falls, kidney problems, or other factors that raise bleeding risk. The Amulet device offers these patients a physical, permanent solution instead of a daily medication.
How the Amulet Device Is Built
The Amulet is made from nitinol, a flexible metal alloy that can compress for delivery through a catheter and then spring back to its intended shape once inside the heart. It has two main parts: a lobe and a disc, connected by a short flexible waist. This dual-seal design is what sets the Amulet apart from older devices.
The lobe anchors deep inside the left atrial appendage, fitting snugly into the neck of the pouch. It has six to ten pairs of small stabilizing wires around its rim that grip the tissue and keep the device from shifting. The disc sits on the outside, covering the opening of the appendage like a cap and creating a second layer of closure against the heart wall. Both components have polyester fabric patches sewn into them that promote tissue growth, helping the heart’s own lining eventually cover the device completely.
The device comes in a range of sizes, from 16 mm to 34 mm, to fit different anatomies. Smaller sizes (16 to 22 mm) have a lobe length of 7.5 mm, while larger sizes (25 to 34 mm) have a 10 mm lobe with additional stabilizing wires for a more secure fit.
Who Qualifies for the Amulet
The Amulet is specifically approved for people with nonvalvular atrial fibrillation (AFib not caused by a heart valve problem) who are at increased stroke risk based on standard scoring systems that factor in age, history of stroke, heart failure, diabetes, and vascular disease. Candidates must also have a legitimate medical reason to avoid long-term blood thinners. This isn’t a convenience choice: the device is meant for patients whose bleeding risk makes oral anticoagulants genuinely problematic.
Patients do need to tolerate a short course of blood-thinning or antiplatelet medication after the procedure while the device heals into place. If even short-term therapy isn’t feasible, the device may not be appropriate.
What Happens During the Procedure
The Amulet is implanted through a catheter-based procedure, meaning there’s no open-heart surgery. A thin tube is guided through a vein, typically in the leg, up to the heart. The doctor crosses from the right side of the heart to the left through a small puncture in the wall between the upper chambers (a transseptal puncture), then navigates to the left atrial appendage.
Using imaging guidance, the lobe is deployed first inside the appendage. The doctor confirms it’s anchored properly and sitting perpendicular to the appendage’s axis before pulling back the delivery sheath to release the disc, which unfolds to cover the opening. The disc must sit flush against the surrounding tissue with no gaps. If positioning isn’t ideal, the device can be recaptured and repositioned before final release. Acute implant success in clinical trials reached 98.4%.
How It Compares to the Watchman
The Watchman device, made by a different manufacturer, was the first FDA-approved left atrial appendage closure device and remains the Amulet’s primary competitor. The most important structural difference is that the Watchman uses a single-lobe design, while the Amulet’s lobe-plus-disc creates a dual seal.
This dual-seal approach makes the Amulet less prone to side leaks, where blood seeps around the edges of the device. The Watchman’s single concave shape is more susceptible to these gaps by geometry. On the other hand, the Amulet is somewhat more prone to “intradevice” leaks, where blood passes through the device itself, partly because the Amulet’s lobe is shorter (10 to 12 mm versus the Watchman’s 14 to 35 mm) and lacks fabric covering on the lobe portion.
In terms of what matters most to patients, the five-year results from the head-to-head Amulet IDE trial found identical annual stroke rates of 1.6% per year for both devices. The composite of stroke or systemic embolism was also similar: 7.4% for Amulet versus 7.1% for Watchman over five years. One notable finding: strokes that did occur in Amulet patients tended to be less severe. Device-related complications like clots forming on the device or significant leaks preceded strokes and cardiovascular deaths more than twice as often in the Watchman group (63 events) compared to Amulet (31 events).
Risks and Complications
The Amulet procedure carries real but manageable risks. In the IDE trial comparing it to the Watchman, procedure-related complications were higher for the Amulet at 4.5% versus 2.5% for the Watchman. The difference was driven primarily by higher rates of pericardial effusion (fluid collecting around the heart) and occasional device embolization (the device shifting from its intended position). Importantly, all pericardial effusion cases resolved without lasting harm, and none required emergency surgery or resulted in death.
These complications were most common early in the learning curve as doctors gained experience with the device. Device-related blood clot formation on the Amulet surface occurred in about 3.3% of patients by 18 months, which was actually lower than the 4.5% rate seen with the Watchman.
Recovery and Life After Implantation
After the procedure, patients typically take a short course of antiplatelet medications (similar to aspirin-class drugs) to prevent clots from forming on the device surface while the heart tissue grows over it. Follow-up imaging, usually with a transesophageal echocardiogram, is performed in the weeks after implantation to confirm the device is properly seated and no significant leaks are present.
The Amulet demonstrated superiority over the Watchman in achieving complete closure of the appendage at both 45 days and 12 months. Once the device is fully incorporated into the heart tissue, the goal is for patients to stop taking blood thinners entirely, which is the whole point of the procedure. The device is permanent and requires no batteries, replacement, or maintenance.