The objectives of the study are:

• To determine the efficacy of the Figulla Flex II device compared with that of the Amplatzer ASO device for transcatheter closure of secundum atrial septal defects
• To determine the safety of the Figulla Flex II device compared with that of the Amplatzer ASO device for transcatheter closure of secundum atrial septal defects

This is a randomized, controlled, multi-centre trial of the efficacy and safety of the Occlutech septal occluder (Figulla Flex II) compared to the AGA septal occluder (Amplatzer ASO) for transcatheter closure of secundum atrial septal defects in patients.

Inclusion criteria A patient will be eligible for study participation if he/she meets the following criteria:

1. Able to fluently speak and understand the language in which the study is being conducted
2. Has ostium secundum atrial septal defect
3. Has a defect hole with a diameter of < 38 mm
4. Has a left-to-right shunt with a Qp/Qs ratio of . 1.5:1 or the presence of right ventricular volume overload determined by transthoracic echo (TTE) or clinical symptoms due to the atrial septal defect
5. Has a distance of > 5 mm from the margins of the defect(s) to the coronary sinus, arterioventricular (AV) valves and right upper pulmonary vein as measured by echocardiography
6. Agrees to participate in the study and comply with the follow-up schedule
7. Is willing to freely give (or Legally Authorized Representative is willing to freely give) Informed Consent prior to treatment
8. Willing to return for the post-treatment evaluation. Exclusion criteria

A patient will be excluded from the study if he/she meets the following criteria:

1. Has multiple defects which can�ft adequately be covered by the device

2. Has associated congenital cardiac anomalies which require cardiac surgery

   a. Has a known sensitivity to contrast media that cannot be controlled adequately with pre-medication.

3. Patient is currently participating in another clinical device or drug trial that has not completed its primary endpoint or that will clinically confound the current study endpoints or does not permit subjects to participate in other studies. Typically, subjects that are involved in the long-term surveillance phase of a clinical study are eligible.

4. Has ostium primum atrial septal defects

5. Has sinus venosus atrial septal defects

6. Has partial anomolous pulmonary venous drainage

7. Has pulmonary vascular resistance above 7 Woods units or a right-toleft shunt at the atrial level with a peripheral arterial saturation less than 94%

8. Has a recent myocardial infarction, unstable angina and decompensated congestive heart failure (CHF)

9. Has right and/or left ventricular decompensation with ejection fraction of < 30%

10. Has an active bacterial and/or viral infection

11. Has any type of serious infection < 1 month prior to the procedure

12. Has malignancy where life expectancy is < 2 years

13. Has demonstrated intracardiac thrombi on echocardiography

14. Weighs < 8 kg

15. Has gastritis, gastric ulcer, duodenal ulcer, etc. and other contraindications to aspirin therapy unless other anti-platelet agents can be administered for 6 months

16. Has an unstable condition or otherwise thought to be unreliable or incapable of complying with the requirements of the clinical investigational plan (CIP).

17. Has any disorder that, in the opinion of the Investigator, might interfere with the conduct of the study.

Inclusion Criteria:

A patient will be eligible for study participation if he/she meets the following criteria:

1. Able to fluently speak and understand the language in which the study is being conducted
2. Has ostium secundum atrial septal defect
3. Has a defect hole with a diameter of < 38 mm
4. Has a left-to-right shunt with a Qp/Qs ratio of ≥ 1.5:1 or the presence of right ventricular volume overload determined by transthoracic echo (TTE) or clinical symptoms due to the atrial septal defect
5. Has a distance of > 5 mm from the margins of the defect(s) to the coronary sinus, arterioventricular (AV) valves and right upper pulmonary vein as measured by echocardiography
6. Agrees to participate in the study and comply with the follow-up schedule
7. Is willing to freely give (or Legally Authorized Representative is willing to freely give) Informed Consent prior to treatment
8. Willing to return for the post-treatment evaluation

Exclusion Criteria:

1. Has multiple defects which can't adequately be covered by the device

2. Has associated congenital cardiac anomalies which require cardiac surgery

   a. Has a known sensitivity to contrast media that cannot be controlled adequately with pre-medication.

3. Patient is currently participating in another clinical device or drug trial that has not completed its primary endpoint or that will clinically confound the current study endpoints or does not permit subjects to participate in other studies. Typically, subjects that are involved in the long-term surveillance phase of a clinical study are eligible.

4. Has ostium primum atrial septal defects

5. Has sinus venosus atrial septal defects

6. Has partial anomolous pulmonary venous drainage

7. Has pulmonary vascular resistance above 7 Woods units or a right-toleft shunt at the atrial level with a peripheral arterial saturation less than 94%

8. Has a recent myocardial infarction, unstable angina and decompensated congestive heart failure (CHF)

9. Has right and/or left ventricular decompensation with ejection fraction of < 30%

10. Has an active bacterial and/or viral infection

11. Has any type of serious infection < 1 month prior to the procedure

12. Has malignancy where life expectancy is < 2 years

13. Has demonstrated intracardiac thrombi on echocardiography

14. Weighs < 8 kg

15. Has gastritis, gastric ulcer, duodenal ulcer, etc. and other contraindications to aspirin therapy unless other anti-platelet agents can be administered for 6 months

16. Has an unstable condition or otherwise thought to be unreliable or incapable of complying with the requirements of the clinical investigational plan (CIP).

17. Has any disorder that, in the opinion of the Investigator, might interfere with the conduct of the study.