Device-related thrombus (DRT) is a recognized complication following left atrial appendage closure (LAAC), with implantation depth proposed as a potential determinant. This multicentre observational study using patient-specific computational fluid dynamics (CFD), published in EuroIntervention, assessed the relationship between device positioning, flow characteristics, and DRT risk.

A total of 285 patients undergoing LAAC with either Amplatzer Amulet or WATCHMAN devices across 10 centres were included. Postprocedural computed tomography and echocardiography-derived parameters were used to assess local blood flow dynamics. Patients were stratified based on implantation depth into proximal and distal groups.

The primary analysis compared CFD-derived indices, including device surface velocity index (DSVI), endothelial cell activation potential (ECAP), and the presence of eddies or stagnated flow. Secondary analyses evaluated associations between these indices and DRT occurrence.

Proximal implantation (57.2%) was associated with more favorable flow characteristics, including higher DSVI (0.11 vs 0.09 m/s; p=0.002), lower ECAP (0.75 vs 0.90; p=0.003), and fewer recirculating flow regions (40.5% vs 74.6%; p<0.001) compared with distal placement. Greater implantation depth was associated with worsening flow parameters and a higher incidence of DRT. A composite CFD-derived risk score incorporating ECAP, implantation depth, and flow complexity showed higher discrimination for DRT (AUC 0.81) compared with anatomical depth alone (AUC 0.71).

These findings indicate that deeper LAAC implantation is associated with adverse flow profiles associated with device-related thrombus. CFD-based flow assessment may provide incremental value for risk stratification, although further validation is required.