Impact of Watchman and Amplatzer Devices on Left Atrial Appendage Adjacent Structures and Healing Response in a Canine Model

Objectives: This study was designed for conducting a comparative evaluation of the healing response after Watchman (WM) (Boston Scientific, Plymouth, Minnesota) and Amplatzer Cardiac Plug (ACP) (St. Jude Medical, Minneapolis, Minnesota) in a canine left atrial appendage (LAA) model.

Background: There is no direct comparison of the WM and ACP device in pre-clinical or clinical settings.

Methods: The LAA from canine (n = 6) and human (n = 19) hearts were compared to determine the feasibility of the canine model and its relevance to clinical applications. Subsequently, implantation of WM and ACP in the canine LAA was performed (n = 3 per device) to evaluate the device conformation to the LA anatomy as well as the healing response at 28 days.

Results: The LAA is a variable tubular structure in both canine and human hearts. Gross examination showed that the WM was properly seated inside the LAA ostium, in comparison to the ACP where the disk was outside of the LAA orifice and extended to the edge of the left superior pulmonary vein and mitral valve. At 28 days, complete neo-endocardial coverage of the WM was observed; however, the ACP showed an incomplete covering on the disk surface especially at the lower edge and end-screw hub regions.

Conclusions: There are differences in conformation of LAA surrounding structures with variable healing response between WM and ACP after LAA closure in the canine model. WM does not obstruct or impact the LAA adjacent structures, resulting in a favorable surface recovery. In comparison, the disk of ACP could potentially jeopardize LAA neighboring structures and leads to delayed healing.