Techniques are described for occluding the ostium of an appendage. In one example, an implantable medical device for insertion in a left atrial appendage of a patient includes a center hub having a longitudinal axis and a first side and a second side, a plurality of compression springs, each of the plurality of compression springs extending radially from the center hub, and a cover disposed about the compression springs and engaged to center hub on both the first side and the second side.
