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Randomized Controlled Trial
. 2025 Jul;11(7):1543-1554.
doi: 10.1016/j.jacep.2025.02.016. Epub 2025 Apr 9.

Characterization and Clinical Outcomes of High-Risk Device-Related Thrombus in the Amulet IDE Trial

Jens Erik Nielsen-Kudsk  1 , Boris Schmidt  2 , Stephan Windecker  3 , Neeraj Shah  4 , William Gray  5 , Christopher R Ellis  6 , Konstantinos Koulogiannis  7 , Jordan A Anderson  8 , Ryan Gage  8 , Dhanunjaya Lakkireddy  9
Affiliations
Randomized Controlled Trial

Characterization and Clinical Outcomes of High-Risk Device-Related Thrombus in the Amulet IDE Trial

Jens Erik Nielsen-Kudsk et al. JACC Clin Electrophysiol. 2025 Jul.

Abstract

Background: Characteristics of device-related thrombus (DRT) may differ between types of left atrial appendage occlusion devices, and the association of different DRT characteristics to clinical outcomes is largely unknown.

Objectives: The incidence, characteristics, and clinical outcomes through 5 years of high- and low-risk DRTs were assessed in the Amulet IDE trial (AMPLATZER Amulet Left Atrial Appendage Occluder [LAAO] Investigational Device Exemption [IDE] Trial).

Methods: An independent core laboratory analyzed all available images at the required 45-day and 12-month visits, and clinical events were reported through 5 years' post-left atrial appendage occlusion.

Results: Of the 1,788 patients with a successful device implant, DRT was observed in 3.3% (30 of 903) and 4.5% (40 of 885) of Amulet and Watchman 2.5 device patients throughout 12 months, respectively (P = 0.192). DRTs were successfully classified as high risk if pedunculated, mobile, >3 mm in thickness, or without continuation onto the left atrial wall. A significantly higher incidence of high-risk DRTs was observed on the Watchman 2.5 device (4.0% [35 of 885]) compared with the Amulet occluder (2.2% [20 of 903]) (P = 0.030). Most low-risk DRTs resolved (12 of 15), whereas high-risk DRTs remained mostly unresolved (34 of 55). Through 5 years, all clinical outcome rates were numerically higher in the high-risk DRT group compared with the low-risk DRT or no-DRT group; significance was observed in the composite of stroke, systemic embolism, or cardiovascular death (30.4% vs 19.9%; HR: 1.74; 95% CI: 1.03-2.92; P = 0.037) and cardiovascular death (26.4% vs 14.5%, HR: 2.09; 95% CI: 1.20-3.66; P = 0.009).

Conclusions: High-risk DRTs were observed in a higher number of Watchman 2.5 device patients compared with Amulet occluder patients. The composite of stroke, systemic embolism, or cardiovascular death occurred more often in patients with high-risk DRTs compared with those with low-risk DRTs or no DRTs. (AMPLATZER Amulet Left Atrial Appendage Occluder [LAAO] Investigational Device Exemption [Amulet IDE Trial]; NCT02879448).

Keywords: Amulet; Watchman; atrial fibrillation; device-related thrombus; left atrial appendage occlusion; stroke.

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Conflict of interest statement

Funding Support and Author Disclosures Abbott funded the Amulet IDE trial. No funding was provided for the current analysis. Dr Nielsen-Kudsk has received institutional research grants from Abbott and Boston Scientific. Dr Schmidt has received speaker honorarium and consulting fees from Abbott, Boston Scientific, Biosense Webster, and Medtronic. Dr Windecker reports research, travel, or educational grants to the institution without personal remuneration from Abbott, Abiomed, Amgen, AstraZeneca, Bayer, Braun, Biotronik, Boehringer Ingelheim, Boston Scientific, Bristol Myers Squibb, Cardinal Health, Cardiovalve, Cordis Medical, CorFlow Therapeutics, CSL Behring, Daiichi Sankyo, Edwards Lifesciences, Farapulse Inc, Fumedica, Guerbet, Idorsia, Inari Medical, Infraredx, Janssen-Cilag, Johnson & Johnson, MedAlliance, Medicure, Medtronic, Merck Sharp & Dohm, Miracor Medical, Novartis, Novo Nordisk, Organon, OrPha Swiss, Pharming Technologies B.V., Pfizer, Polaris, Regeneron, Sanofi-Aventis, Servier, Sinomed, Terumo, Vifor, and V-Wave. He also served as advisory board member and/or member of the steering/executive group of trials funded by Abbott, Abiomed, Amgen, AstraZeneca, Bayer, Boston Scientific, Biotronik, Bristol Myers Squibb, Edwards Lifesciences, MedAlliance, Medtronic, Novartis, Polaris, Recardio, Sinomed, Terumo, and V-Wave with payments to the institution but no personal payments; and is also a member of the steering/executive committee group of several investigator-initiated trials that receive funding by industry without impact on his personal remuneration. Dr Gray serves as a consultant or has received grant support from Boston Scientific, Cook Medical, Medtronic, Surmodics, and Philips. Dr Ellis has received institutional research grants from Boehringer Ingelheim, Medtronic, and Boston Scientific; and consulting/advisory fees for Medtronic Inc, Abbott Medical Inc, Boston Scientific Inc, and AtriCure Inc. Dr Koulogiannis has received speaker honorarium from Abbott and consulting fees from Edwards Lifesciences. Dr Anderson and Mr Gage are employees of Abbott. Dr Lakkireddy has received research and educational grants to the institution from Abbott, AtriCure, Alta Thera, Medtronic, Biosense Webster, Biotronik, and Boston Scientific; and has received speaker honorarium from Abbott, Medtronic, Biotronik, and Boston Scientific. Dr Shah has reported that he has no relationships relevant to the contents of this paper to disclose.

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