ADVANCE ASO AMPLATZER™ Atrial Septal Occluder Post Market Surveillance Study

Inclusion Criteria: To participate in this clinical investigation, the patient must meet all of the following inclusion criteria: 1. Patient indicated for ASD closure who has echocardiographic evidence of ostium secundum atrial septal defect and clinical evidence of right ventricular volume overload (such as, 1.5:1 degree of left-to-right shunt or RV enlargement) and is implanted with the ASO device Note: This does not include the indication for closure of a fenestration following a fenestrated Fontan procedure 2. Patient is willing and able to complete the follow-up requirements of this study 3. Patient signs the informed consent (or a legal representative signs the informed consent.) Exclusion Criteria: Patient is not eligible for clinical investigation participation if he/she meets any of the following exclusion criteria: 1. Patient is known to have extensive congenital cardiac anomaly which can only be adequately repaired by way of cardiac surgery 2. Patient is known to have sepsis within 1 month prior to implantation, or any systemic infection that cannot be successfully treated prior to device placement 3. Patient is known to have a bleeding disorder, untreated ulcer, or any other contraindications to aspirin therapy (unless another anti-platelet agent can be administered for 6 months) 4. Patient is known to have a demonstrated intracardiac thrombus on echocardiography 5. Patient whose size (such as, too small for transesophageal echocardiography probe, catheter size) or condition (active infection, etc.) would cause the patient to be a poor candidate for cardiac catheterization 6. Patient has margins of defect that are less than 5 mm to the coronary sinus, AV valves or right upper lobe pulmonary vein