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Amulet occluder shows promise against Watchman device in atrial fibrillation

Patients with NVAF are at increased risk for ischaemic stroke. Oral anticoagulation is recommended to reduce stroke risk, but percutaneous LAA occlusion may be considered in patients with contraindications to long-term anticoagulation due to risk of bleeding.

The Amulet IDE trial was the first multicentre randomized trial comparing the Amulet LAA occluder head-to-head with the Watchman device. Both are percutaneous transcatheter devices intended to prevent the migration of blood clots from the LAA and reduce the incidence of thromboembolic events in patients with NVAF. While both devices close off the LAA, the mechanism differs. The Amulet LAA occluder dual-seals the LAA by two mechanisms using the device’s lobe and disc: 1) filling the neck of the LAA with the lobe and 2) covering the LAA ostium with the disc. In contrast, the Watchman device only fills the body of the LAA.

The trial enrolled patients 18 years of age or older with paroxysmal, persistent, or permanent NVAF and at a high risk of stroke or systemic embolism defined as CHA2DS2-VASc score of 3 or higher or a CHADS2 score of 2 or higher. Patients were screened with transoesophageal echocardiography to ensure suitable LAA anatomy for implanting either device prior to enrolment. As required by the directions for use of the Watchman device, patients had to be suitable for anticoagulation therapy for six weeks post-implantation.

A total of 1,878 patients were randomized 1:1 to receive an Amulet LAA occluder or a Watchman device. All patients were required to complete clinical follow-up at discharge, 45 days, 3, 6, 9, 12 and 18 months, and 2, 3, 4 and 5 years. Follow-up beyond 18 months is currently ongoing.

The trial had three primary endpoints. The primary safety endpoint was a composite of procedure-related complications, all-cause death, or major bleeding through 12 months. The primary effectiveness endpoint was a composite of ischaemic stroke or systemic embolism through 18 months. The primary mechanism of action endpoint was device based LAA closure (residual jet around the device 5 mm or less) as assessed by an independent core laboratory on transoesophageal echocardiography at the 45-day visit. This endpoint provided an indication of how well the device was sealing off the LAA.

The average age of participants was 75 years and 60% were men. Patients most frequently sought an alternative to anticoagulation therapy due to a history of major or minor bleeding (~54%) or high bleeding risk (~21%). Patients were at a high risk of stroke, with a mean CHA2DS2-VAScscore of ~4.6. The device was successfully implanted as randomized in 98.4% of Amulet patients and 96.4% of Watchman patients. Most (82.0%) Watchman patients were discharged on warfarin plus aspirin. In contrast, 75.7% of Amulet patients were discharged on dual antiplatelet therapy (aspirin and clopidogrel) and 20.0% were on anticoagulation plus aspirin.

Device based LAA closure rates were higher and demonstrated superiority of the Amulet LAA occluder compared with the Watchman device (98.9% versus 96.8%; difference=2.03; 95% confidence interval [CI] 0.41–3.66; p<0.001 for noninferiority; p=0.003 for superiority). A detailed analysis of residual jet at 45 days revealed no flow around the device in 63% of Amulet patients compared to 46% of Watchman patients. The Amulet LAA occluder was noninferior to the Watchman device for the primary safety endpoint (14.5% versus 14.7%; difference=-0.14; 95% CI -3.42–3.13; p<0.001 for noninferiority) and the primary effectiveness endpoint (2.8% versus 2.8%; difference=0.00; 95% CI -1.55–1.55; p<0.001 for noninferiority).

Principal investigator Professor Dhanunjaya Lakkireddy of the Kansas City Heart Rhythm Institute and Research Foundation, US said: “The Amulet LAA occluder was superior with respect to LAA closure and noninferior with respect to safety and effectiveness for stroke prevention in patients with NVAF compared to the Watchman device. The dual seal design of the Amulet LAA occluder helps to overcome the limitations of a single seal device, including but not limited to short LAA length, proximal lobes near the ostium, and very large ostia. In addition, immediate closure of the LAA with the Amulet disc allows some patients to be treated without the need for anticoagulation therapy after the procedure.”