WATCHMAN FLXTM Pro
Left Atrial Appendage Closure Device
featuring HEMOCOATTM Technology
Enhanced thromboresistance and endothelialization of a novel fluoropolymer-coated Left Atrial Appendage Closure Device.1
1. Saliba et al. Enhanced Thromboresistance and Endothelialization of a Novel Fluoropolymer-Coated Left Atrial Appendage Closure Device, JACC: Clinical Electrophysiology, 2023.
The fluoropolymer-coated WATCHMAN FLX Pro device showed significantly less thrombus and reduced inflammation in a challenging canine model. Mechanistic studies demonstrated that the WATCHMAN FLX Pro device binds more albumin, leading to reduced platelet activation, less inflammation, and greater endothelial coverage (EC).
Study design and methods
- This study examined the antithrombotic properties
and endothelial coverage of the fluoropolymer-coated WATCHMAN FLX Pro and WATCMAN FLX devices using several experimental setups (Figure 1). - Canines were randomized for implantation with WATCHMAN FLX Pro or WATCHMAN FLX devices and given no post-implant antithrombotic/antiplatelet agents.
- DRT was assessed using transesophageal echocardiography (TEE) and verified histologically.
- The biochemical mechanisms associated with the coating were assessed by using flow loop experiments to quantify albumin adsorption, platelet adhesion, and porcine implants to quantify EC and the expression of markers of endothelial maturation (ie, vascular endothelial-cadherin/p120-catenin).
Figure 1. Study Flow and Subject Preparation. CM = confocal microscopy; SEM = scanning electron microscopy.
Albumin flow loop experiment
The WATCHMAN FLX Pro devices demonstrated significantly greater percent area with albumin adsorption, resulting in a surface less activating to platelets.
Confocal microscopy images magnified 20x showing albumin proteins tagged with green fluorescent dye, with significantly greater proportion on WATCHMAN FLX Pro devices.
Platelet binding blood loop experiment
Following exposure to the 3-hour human blood flow loop, the WATCHMAN FLX Pro devices exhibited significantly less percent area with platelet binding as a result of preferential albumin adsorption.
Confocal microscopy images showing platelet deposition (red) on fabric of devices, with significantly less platelets on WATCHMAN FLX Pro devices.
Inflammation and thrombus assessment at 3 and 14 days
The percentage of PET knots surrounded by severe inflammation (purple dots) was significantly less at 3 days with the WATCHMAN FLX Pro device, while thrombus maximal thickness was also significantly less in WATCHMAN FLX Pro at 3- and 14 days compared to the WATCHMAN FLX device.
Representative images of inflammation surrounding knot(s) at 3 days and images of thrombus on devices at 14 days.
Thrombus and gross healing assessment in canine models
In non-anticoagulated canine models, the WATCHMAN FLX Pro device showed significantly fewer devices with excess thrombus (>3 mm) on TEE at 14 days, 28 days, and 45 days. At 45-day gross examination, the WATCHMAN FLX Pro devices showed a smooth, neo-endocardial covering (absence of acute thrombus material) in all 6 implants compared to only 2 of 6 in the WATCHMAN FLX device.
Representative serial TEE images at 14, 28 and 45 days after implantation in the canine models. Yellow arrows indicate DRT >3 mm, while black arrows highlight thrombus on the surface of the WATCHMAN FLX device.
Endothelial coverage and cell function in swine models
CM and SEM examination of endothelial coverage at 90 days of the luminal surface in non-anticoagulated swine models demonstrated significantly greater coverage on the surface of the WATCHMAN FLX Pro devices. This is supported by areas of co-expression of vascular endothelial [VE]-cadherin (VE-Cad) and p120-catenin (p120), demonstrating mature endothelium.
Representative images of endothelial coverage assessed by CM and SEM. Dotted boxes are shown as CM images with expression of vascular endothelial [VE]-cadherin and p120-catenin, which is considered the last step in the process of endothelial maturation. The surface of the WATCHMAN FLX device is covered with immature endothelium, as characterized by either the lack of or patchy co-expression of VE-Cad/p120 signal.
Key takeaway
These data confirm the antithrombogenic properties of the fluoropolymer-coated WATCHMAN FLX Pro device. The WATCHMAN FLX Pro device showed significantly greater albumin adsorption and less platelet activation, driving inhibition of platelet-driven thrombus, and led to significantly greater endothelial coverage in non-anticoagulated swine models at 90 days.
