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

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).