A device for closing a left atrial appendage of a patient comprising a containment member having a first configuration for passage into the left atrial appendage and a second larger configuration, and a wire movable into the containment member in situ to expand the containment member in the left atrial appendage to the second configuration. The or each diatomic bridge extends between two atoms in the component. The batt is compacted and unified into its stable final shape by heating and soft-pressing, which causes at least a portion of the synthetic fibers to soften andor melt and thereby bond the needled cotton shoddy and synthetic fibers together.