Effect of left atrial appendage occlusion device type and position on potential determinants of device-related thrombus

Abstract Introduction Device-related thrombus (DRT) after left atrial appendage occlusion (LAAO) is potentially linked to adverse events. Clinical reports suggest an association between the device type/position and the DRT risk, in-depth studies of its mechanistic basis are needed. Purpose To generate in silico model with precise geometry of LAAO devices and assess the impact of device type and position on local hemodynamics and surrogate markers of DRT risk. Methods Watchman (plug-type device) and Amulet (pacifier device) LAAO devices were modeled with precise geometry and virtually implanted in different positions into a patient-specific left atrium. Using computational fluid dynamics, the following surrogate markers of thrombogenicity were quantified: residual blood, wall shear stress (WSS) and endothelial cell activation potential (ECAP). Results In comparison to ostium-fitted device positions, deep implantations were associated with more residual blood surrounding the device (after six cardiac cycles: plug-type device 12% vs 8%; pacifier device 6% vs 5%). Furthermore, deep implantations resulted in lower average WSS that indicates increased risk in platelet adhesion (plug-type device 0.21 vs. 0.26 Pa; pacifier device 0.30 vs 0.35 Pa) and higher ECAP that represents higher potential in endothelial dysfunction (plug-type device 2.23 vs. 0.85 Pa-1; pacifier device 0.16 vs 0.10 Pa-1). For plug-type device, an off-axis orientation towards mitral valve resulted in even more residual blood (15% vs. 8%), higher ECAP (1.10 vs. 0.85 Pa-1) and a similar average WSS as compared to an ostium-fitted device position. In addition, the precise geometry of the LAAO device models allowed indication of residual blood accumulation on the device’s atrial surface surrounding the threaded insert as well as on the lateral device surface and on the left atrium tissue around the device landing zone. Similarly, low WSS and high ECAP were mostly found in these areas, suggesting an increased risk for potential thrombus in these areas, which corresponds to the clinical observational series. Conclusions This study demonstrated the effect of LAAO device type and position on potential DRT risk factors. In comparison to the plug-type device, the pacifier device showed lower blood stasis, platelet adhesion and endothelial dysfunction and, therefore, lower DRT risk. For both device types, deep implantations are associated to higher surrogate markers of DRT compared to ostium-fitted device positions. In addition, an off-axis device position of plug-type device were associated with higher DRT risk.