BACKGROUND: This study aims to assess how Watchman FLX (Boston Scientific) and Amplatzer Amulet (Abbott) devices for left atrial appendage occlusion (LAAO) impact the flow dynamics in the LA and the risk of device-related thrombosis (DRT).

METHODS: Flow simulations were carried out for 12 AF patients before and after undergoing LAAO. Six patients had Watchman FLX while the other six had Amulet devices, of which three in each group had DRT. The flow parameters investigated included the LA velocities, pressure, time averaged wall shear stress (TAWSS), oscillatory shear index (OSI), and relative residence time (RRT). Low TAWSS and high OSI and RRT are generally associated with flow stasis and thrombosis.

RESULTS: LA flow dynamics differed significantly between the two groups. On average, after LAAO, the Amulet patients exhibited a 25% increase in TAWSS and 24% decrease in RRT while the Watchman FLX patients exhibited, on average, a 24% decrease in TAWSS and a 23% increase in RRT. Both populations experienced an increase in LA pressure (~10% for Amulet patients and 16% for Watchman FLX patients). Increased DRT volume seems to be correlated with low TAWSS and elevated RRT.

CONCLUSION: This preliminary study suggests that the Amulet device might be associated with improved LA flow dynamics and a potentially lower incidence of DRT compared with the Watchman. However, a larger clinical study is needed to confirm these findings.