(A) Opened left atrium showing the device seated within the appendage orifice. There are small linear gaps between the concave surface of the device fabric and the edge of the appendage ostium margin (arrows), though the appendage cavity behind the covered membrane was healing with endocardium so no thrombi could form nor exit this appendage. (B) Sagittal section through the center of the appendage and device. The section shows tight apposition of the device to the appendage wall and sealing of the device-appendage wall interface. Inside the device, the reddish-pink areas indicate fibrous organization. Toluidine blue and basic fuchsin stain. (C) Close-up view through the center of the device showing neointimal coverage over the surface. Toluidine blue and basic fuchsin stain, 1.25×. (D) Close-up view of the device surface showing effective sealing of the atrial wall-device interface (arrow). Brown areas represent hemosiderin resulting from red cell breakdown. Toluidine blue and basic fuchsin stain, 4×.