Background: Device-related thrombus (DRT) after left atrial appendage occlusion (LAAO) is potentially linked to adverse events. Although clinical reports suggest an association between the device position and the DRT risk, its mechanistic basis is poorly understood. This in silico study aimed to assess the impact of the position of a plug-type LAAO device on surrogate markers of DRT risk.

Methods: 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 an ostium-fitted device position, a deep implantation was found to be associated with more residual blood surrounding the device  (12% vs. 8%), lower average WSS (0.21 vs. 0.26 Pa) and higher ECAP (2.23 vs. 0.85 Pa^-1) after six cardiac cycles. An off-axis device orientation 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. The precise geometry of the LAAO device model allowed prediction 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 an effect of LAAO device position on potential DRT risk factors in terms of blood stasis, platelet adhesion and endothelial dysfunction, confirming the clinical observation. A deep implantation of the occluder and an off-axis device position were associated with in vitro markers of DRT risks compared to an ostium-fitted device position.