Impact of device implantation depth on blood flow dynamics after left atrial appendage closure

BACKGROUND: Device-related thrombus (DRT) remains a concern after left atrial appendage closure (LAAC), particularly when the device is deeply implanted. However, the mechanistic links between implantation depth, flow dynamics, and DRT risk are not well understood. AIMS: We therefore aimed to evaluate the impact of LAAC device implantation depth on local flow characteristics and its association with DRT using patient-specific computational fluid dynamics (CFD). METHODS: The study included 285 patients undergoing LAAC with either Amplatzer Amulet or WATCHMAN devices at 10 centres. Patient-specific CFD simulations were performed using postprocedural computed tomography and echocardiography-derived boundary conditions to assess blood flow dynamics. The primary endpoint was the comparison of CFD-derived flow indices - device surface velocity index (DSVI), endothelial cell activation potential (ECAP), and the presence of eddies/stagnated flow - between proximal and distal device implantation groups. Secondary analyses explored the relationship between these flow features and DRT. RESULTS: Proximal implants (57.2%) showed more favourable flow patterns: higher DSVI (0.11 m/s vs 0.09 m/s; p=0.002), lower ECAP (0.75 vs 0.90; p=0.003), and fewer recirculating zones (40.5% vs 74.6%; p<0.001). DRT incidence increased with greater implantation depth, paralleled by worsening flow indices. A composite CFD-based DRT risk score, incorporating ECAP, implantation depth, and flow complexity, demonstrated good discrimination (area under the receiver operating characteristic curve [AUC] 0.81), outperforming anatomical depth alone (AUC 0.71). CONCLUSIONS: Deeper LAAC device implantation is associated with adverse flow profiles and a higher risk of DRT. CFD-based flow characterisation may enhance risk stratification beyond anatomical criteria alone. Further studies incorporating clinical variables are warranted to validate these methods.