Preclinical assessment of a modified Occlutech left atrial appendage closure device in a porcine model

Figures

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  Figure 1. Occlutech Plus LAA closure device and delivery system. (A) The modified Occlutech LAA closure device consists of a proximal (PU membrane covered) and a distal (nitinol mesh) part. Distal positioned loops and newly developed anchors situated between the proximal and distal device parts secure anchoring within the LAA. The nitinol mesh has self-expanding properties ensuring self-modeling of the device within the LAA. The polyurethane (PU) covering serves as barrier excluding blood flow from the LA to the LAA. The connection hub serves as docking for the delivery system. B) Comparison of new device characteristics compared to the predecessor. C) Delivery system: the dilator (1) made from smooth conformable low friction radio-opaque material is inserted into the steerable delivery sheet (2) consisting of a thin braided wall and a soft flexible tip allowing bidirectional deflection up to 180°. The sheath has a hemostatic valve and can be connected by an adapter to the loader (4) made of transparent low friction material to allow inspection for air bubbles after pulling the occluder into the loader. Permission for usage of the image granted by OCCLUTECH Holding AG.

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  Figure 2. Study design. Timeline of pre-implantation actions, LAA occlusion procedure and post-implantation activities within the study protocol. 16 animals were used in the study, four were lost at day 0 (implantation). Animal groups 1, 2 and 3 consisted of four animals each that completed follow-up and histopathological evaluation.

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  Figure 3. Imaging and morphological examination at follow up. Fluoroscopic images illustrating LAA anatomy and measurements for device implantation (orifice- red arrow, landing zone- black arrow, LAA length- blue arrow) (A) as well as device implants (asterisk) (B). Anchoring of the device and sealing of the LAA was confirmed by (Doppler)- TEE imaging (C,D). 3-D TEE imaging illustrates occluder position (asterisk) inside the LAA ostium (E). Macroscopic evaluation of LAA device implants (asterisk) was performed (F).

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  Figure 4. Histopathological examination of device and surrounding tissue at follow up. 4 wk fu: (A) Macroscopic evaluation Device in situ. Complete sealing within the LAA ostium. Fibrin accumulation on the surface of the device. (B) Thrombus Thrombus in the border areas consists of loose connective tissue with erythrocytes (arrow) as well as moderate numbers of inflammatory cells (PMN, lymphocytes, few multinucleated giant cells). Most of the thrombotic material consists of coagulated blood (asterisk). (C) Membrane The cover of the PU membrane shows discrete connective tissue proliferation. In an islet-like pattern the connective tissue is thickened (infiltration with PMN and lymphocytes). On the connective tissue surface endothelial cells can be identified (arrow). (D) Anchoring Ingrowth of the device (struts indicated by asterisk) can be characterized by medium strength connective tissue (red arrow). A discrete to moderate inflammatory reaction consisting of PMN and lymphocytes can be depicted (black arrow). B-D hematoxylin–eosin (HE) staining.

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  Figure 5. Histopathological examination of device and surrounding tissue at follow up. 8 wk fu: (A) Macroscopic evaluation Device in situ. Complete sealing within the LAA ostium. Connective tissue progresses on the device surface. (B) Thrombus Thrombus consists of loose connective tissue with nest-like calcifications (arrow). Plaques of lymphocytes and diffuse macrophages containing hemosiderin can be appreciated. Connective tissue shows collection of erythrocytes with good vascularization. (C) Membrane: The membrane is covered with connective tissue that is covered by an endothelial monolayer (arrow). (D) Anchoring At the ingrowth area (struts indicated by asterisk) vascularized connective tissue (black arrow) with a discrete lymphocytic inflammation (yellow arrow) is determined. The surrounding myocardium (red arrow) does not show fibrosis. B-D hematoxylin–eosin (HE) staining.

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  Figure 6. Histopathological examination of device and surrounding tissue at follow up. 12 wk fu: (A) Macroscopic evaluation Device sealing the LAA ostium is depicted. Connective tissue covered by an endothelial layer completely fills the device surface. (B) Thrombus Thrombus completely organized by connective tissue (arrow). (C) Membrane The membrane is completely covered with connective tissue that is covered by an endothelial monolayer (arrow). (D) Anchoring In the areas of device ingrowth (black arrow) a cell-rich connective tissue developed with discrete diffuse inflammation consisting of PMN and lymphocytes (asterisk). B-D hematoxylin–eosin (HE) staining.