The objective of this PMCF study is to:
* confirm the safety and performance of the AcuMarkTM Sizing Balloon * identify previously unknown side-effects * monitor the identified side-effects (related to the procedure or to the medical devices)
Patients who have been confirmed with single secundum atrial septal defect (ASD) by echocardiography;
The anatomy of ASD is suitable for percutaneous closure;
Patients are scheduled to perform ASD closure;
Patients or legally authorized representative(s) who are willing and capable of providing informed consent.
Any contraindication for ASD closure;
Patients have ostium primum ASD or coronary sinus ASD;
Patients who are pregnant or breastfeeding;
Patient is currently participating in another clinical trial that has not yet completed its primary endpoint.