The present invention provides a device for occluding an anatomical aperture, such as an atrial septal defect (ASD) or a patent foramen ovale (PFO). The occluder includes two sides connected by a central tube. In some embodiments, the occluder is formed from filaments that are joined together to define a substantially cylindrical form with openings defining struts. Upon the application of force, the struts deform into loops. The loops may be of various shapes, sizes, and configurations, and, in at least some embodiments, the loops have rounded peripheries. The occluder further includes a catch system that maintains its deployed state in vivo. When the occluder is deployed in vivo, the two sides are disposed on opposite sides of the septal tissue surrounding the aperture and the catch system is engaged so that the occluder closes the aperture.