Incidence, Characterization, and Clinical Impact of Device-Related Thrombus Following Left Atrial Appendage Occlusion in the Prospective Global AMPLATZER Amulet Observational Study.

Objectives: This study sought to report the incidence, characteristics, and clinical impact of device-related thrombus (DRT) following left atrial appendage occlusion (LAAO) with the AMPLATZER Amulet device (Abbott, Plymouth, Minnesota).

Background: DRT is a potential serious complication of LAAO, but the incidence and clinical impact of DRTs in a real-world setting are not well characterized.

Methods: A total of 1,088 patients were enrolled in a multicenter prospective study and followed for 1 year. All events were adjudicated by an independent committee, including the presence of DRT. Patients with DRT were reviewed for suboptimal device implantation and characterization of DRT formation. Multiple Cox regression was performed to identify predictors of DRT formation.

Results: Device implantation was successful in 1,078 (99%) patients, with 1-year follow-up completed in 96.3% of patients. A total of 18 DRTs occurred in 17 patients (1.7%/year), as a second DRT developed following complete resolution of an initial DRT in 1 patient. The left upper pulmonary vein ridge was not covered by the Amulet disc in 82% of DRT patients, indicating suboptimal implantation, with most thrombus developing in the untrabeculated area of the LAA ostium between the pulmonary vein ridge and the upper edge of the disc. Three (18%) DRT patients had an ischemic stroke, all within 3 months of DRT diagnosis. Patients with a DRT were at a greater risk for ischemic stroke or transient ischemic attack compared with non-DRT patients (hazard ratio: 5.27; 95% confidence interval: 1.58 to 17.55; p = 0.007). Larger LAA orifice width was a predictor of DRT formation (hazard ratio: 1.09; 95% confidence interval: 1.00 to 1.19; p = 0.04).

Conclusions: Following LAAO with the AMPLATZER Amulet device, DRT was observed infrequently. Although the presence of DRT was associated with an increased rate of ischemic stroke or transient ischemic attack as compared with patients without DRT, the large majority of DRT patients (82%) did not experience any ischemic neurologic events.