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The Amplatzer Amulet left atrial appendage (LAA) occluder was at least as good as the first-generation Watchman in keeping strokes down, according to the randomized IDE trial that helped convince FDA to approve the Amulet earlier this month.

In people with non-valvular atrial fibrillation (Afib) at high risk of stroke, the safety and effectiveness of the Amulet were supported by outcomes after percutaneous LAA closure:

• Fewer residual leaks around the implant at 45 days: mechanism of action endpoint 98.9% with Amulet vs 96.8% with Watchman (Amulet meeting both non-inferiority and superiority criteria)
• Comparable safety at 12 months: combined procedural complications, all-cause death, and major bleeding rates 14.5% vs 14.7% (Amulet meeting non-inferiority but not superiority)
• Comparable effectiveness at 18 months: ischemic strokes or systemic embolisms reaching 2.8% for both groups (Amulet meeting non-inferiority but not superiority)

At 18 months, device-related thrombus was observed in 3.3% of the Amulet arm and 4.5% of the Watchman arm, reported Dhanunjaya Lakkireddy, MD, of HCA Midwest Health Heart and Vascular Institute in Kansas City, Kansas.

Notably, only 21% of Amulet recipients were discharged on anticoagulation (the rest discharged on dual antiplatelet therapy) compared with 96% of patients after Watchman placement.

Thus, for high-risk Afib patients, the Amulet device offers "immediate closure to reduce the risk of stroke and immediate freedom from oral anticoagulants," Lakkireddy concluded during a Hot Line session at the European Society of Cardiology (ESC) virtual meeting.

"This is great news for patients who are intolerant of even short-term anticoagulation, as those patients currently don't have an 'on-label' option for LAA closure," commented Mohamad Alkhouli, MD, of Mayo Clinic in Rochester, Minnesota.

Amulet IDE counted 78 participating sites in the U.S. and another 30 abroad. With 1,878 people randomized, the study is notable for being the largest trial on percutaneous LAA occlusion to date, commented ESC session discussant Gerhard Hindricks, MD, PhD, of Heart Center Leipzig in Germany.

However, it still doesn't provide information on the efficacy of percutaneous LAA occlusion compared to direct oral anticoagulants for stroke prevention. "This is the key question that I believe is still open," Hindricks said, adding that a direct comparison is "urgently needed."

Watchman candidates currently need to be on anticoagulation for 45 days post-implant or longer depending on whether they have any major leaks on transesophageal echocardiography, commented Antony Chu, MD, of Lifespan Cardiovascular Institute and Brown University in Providence, Rhode Island.

Unlike the Watchman, Amplatzer Amulet consists of a lobe attached to a disk, a design aimed at better suitability for different LAA anatomies.

Thus, following for the device earlier this month, it is more important than ever for operators to perform preprocedural CT scans on their LAA occlusion candidates. Operators shouldn't "wander around" when they start the procedure and decide that they want to switch to one occluder device or another as an afterthought, Lakkireddy urged.

His group initiated the study in 2016, when Watchman was still the only FDA-approved LAA occluder for comparison.

In 2020, the second-generation Watchman FLX replaced the original Watchman on the basis of the PINNACLE FLX study boasting zero leaks exceeding 5 mm at 12 months. Watchman FLX is "clearly a better device" in terms of ease of implantation, safety, device-related thrombus, and leaks, said Vivek Reddy, MD, of Mount Sinai Health System in New York City.

Chu surmised that this device might perform even better than the Amulet if a direct comparison were to be made.

participants had patients randomized to the Amulet or Watchman devices for their LAA occlusion. The cohort had a mean age of 75, and approximately 60% of patients were men. The average CHA_₂DS_₂-VASc score was 4.5 and HAS-BLED scores averaged over 3.

Complications of LAA closure reached 4.5% and 2.5% of Amulet and Watchman groups, respectively, driven by pericardial effusion and device embolization.

These complications can be attributed to a learning curve for U.S. operators, many of whom were unfamiliar with the device prior to their participation in the study, Lakkireddy said. He presented a case sequence analysis suggesting that complication rates come down once operators had seven Amulet cases under their belt.

"I do imagine that just as these complication rates decreased substantially with even just a little clinical experience with Watchman implantation, so too with the Amulet device as it is elaborated in clinical practice," Reddy commented.

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