Kramer, Anders

ABSTRACT 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.

Abstract Aims To assess the reproducibility of interpreting hypoattenuated thickening (HAT) and peridevice leak (PDL) using cardiac computed tomography (CT) imaging following Watchman FLX left atrial appendage closure (LAAC). Methods and results In this multicentre retrospective reproducibility study, 100 anonymized post-LAAC cardiac CT scans were evaluated within the same cardiac phase by an experienced and a novice rater blinded to prior evaluations. All scans were evaluated twice by each rater, assessing overall HAT and PDL categories as well as specific associated findings based on suggested algorithms for post-LAAC interpretation. Inter- and intra-rater agreement and reliability were evaluated using absolute agreement, Cohen’s kappa, and Kendall’s tau for categorical variables, and mean difference, Bland–Altman plots, limits of agreement (lower and upper), and intra-class correlation coefficients (ICCs) for continuous variables. Within overall categories of both HAT and PDL, substantial agreement (kappa ≥0.61) and reliability (Kendall’s tau-b ≥ 0.75) were observed. Specifically, identifying high-grade HAT (kappa ≥0.78) and distal patency (kappa ≥0.85) displayed the highest agreement within HAT and PDL interpretation. Meanwhile, measuring the height of the proximal screw hub cove represented the least reliable HAT assessment among both inter- and intra-rater comparisons (ICC < 0.75), while suspected leak mechanism represented the least reproducible PDL measure. Conclusion Despite only minimal training of one rater, overall high levels of inter- and intra-rater agreement and reliability were observed across the chosen algorithms for interpretation of HAT and PDL following Watchman FLX LAAC. The prognostic implications of the included variables are to be explored in future trials and registries.

Abstract Background The exclusion/occlusion of the left atrial appendage (LAA) is a treatment option for atrial fibrillation (AF) patients who are at high risk of stroke and high risk of bleeding. As the role of the LAA is not well understood or explored, this study aims to assess its role on flow dynamics in the left atrium. Methods Computational fluid dynamics (CFD) simulations were carried out for nine AF patients before and after LAA exclusion. The flow parameters investigated included the LA velocities, Time Averaged Wall Shear Stress (TAWSS), Oscillatory Shear Index (OSI), Relative Residence Time (RRT), and Pressure in the LA. Results This study shows that, on average, a decrease in TAWSS (1.82 ± 1.85 Pa to 1.27 ± 0.96 Pa, p < 0.05) and a slight increase in OSI (0.16 ± 0.10 to 0.17 ± 0.10, p < 0.05), RRT (1.87 ± 1.84 Pa −1 to 2.11 ± 1.78 Pa −1 , p < 0.05), and pressure (−19.2 ± 6.8 mmHg to −15.3 ± 8.3 mmHg, p < 0.05) were observed in the LA after the exclusion of the LAA, with a decrease in low‐magnitude velocities. Conclusion The exclusion of the LAA seems to be associated with changes in LA flow dynamics. Further studies are needed to elucidate the clinical implications of these changes.

Abstract Aims Cardiac computed tomography (CT) is increasingly utilized during follow-up after left atrial appendage closure (LAAC). Hypoattenuated thickening (HAT) is a common finding and might represent either benign device healing or device-related thrombosis (DRT). The appearance and characteristics of HAT associated with the Watchman FLX have not been previously described. Therefore, we sought to investigate cardiac CT findings during follow-up after Watchman FLX implantation with a focus on HAT and DRT. Methods and results Retrospective single-centre, observational study including all patients with successful Watchman FLX implantation and follow-up cardiac CT between March 2019 and September 2021 (n = 244). Blinded analysis of CT images was performed describing the localization, extent, and morphology of HAT and correlated to imaging and histology findings in a canine model. Relevant clinical and preclinical ethical approvals were obtained. Overall, HAT was present in 156 cases (64%) and could be classified as either subfabric hypoattenuation (n = 59), flat sessile HAT (n = 78), protruding sessile HAT (n = 16), or pedunculated HAT (n = 3). All cases of pedunculated HAT and five cases of protruding sessile HAT were considered as high-grade HAT (n = 7). Subfabric hypoattenuation and flat sessile HAT correlated with device healing and endothelialization in histological analysis of explanted devices. Conclusion Subfabric hypoattenuation and flat sessile HAT are frequent CT findings for Watchman FLX, likely representing benign device healing and endothelialization. Pedunculated HAT and protruding HAT are infrequent CT findings that might represent DRT.