A device for closing the left atrial appendage of a patient comprising a retention member composed of a shape memory material and a mesh material supported by the retention member. The retention member has a first elongated configuration for delivery and a second expanded configuration for placement within the left atrial appendage. The mesh is configured to block blot clot migration from the appendage. In the second configuration the retention member moves toward a shape memory position. The retention member has a plurality of appendage wall engagement members to secure the retention member to the appendage.