 The GORE HELEX Septal Occluder is an approved medical device indicated for the transcatheter closure of atrial septal defects ASDs. The purpose of this study is to evaluate the long-term safety and efficacy of the GORE HELEX Septal Occluder in the treatment of ostium secundum atrial septal defects ASDs. This is an FDA Condition of Approval Study. All subjects enrolled in this study will be followed for long-term safety and efficacy of the occluder device through 5 years. 