The purpose of this investigation is to collect data pertaining to the safety and performance of the ACURATE neo (TM) Aortic Bioprosthesis as implanted with the ACURATE neo (TM) TA Transapical Delivery System. This device is intended for treatment of subjects with severe aortic stenosis (AS) who have high risk for conventional aortic valve replacement (AVR) surgery. The ACURATE neo (TM) Aortic Bioprosthesis is intended for use via minimally-invasive transapical implantation in a well-defined population.

This is a single arm, prospective, multicenter non randomised and open trial of the treatment of patients with severe aortic stenosis where conventional aortic valve replacement (AVR) via open heart surgery is considered to be high risk. All patients will be followed up to 5 years after the intervention.

The primary objective is to evaluate the safety and performance of the study device in patients presenting with severe aortic stenosis considered to be high risk for surgery Secondary objective is to evaluate adverse events and study device performance.

Inclusion Criteria:

1. Subject must be at least 18 years old

2. Severe aortic stenosis defined as:

   • Mean aortic gradient > 40 mmHg or
   • Peak jet velocity > 4.0 m/s or
   • Aortic valve area of < 0.8 cm2

3. High risk patient determined by a multidisciplinary heart team consensus (cardiologist and cardiac surgeon) that patient is not a surgical candidate for conventional AVR due to risk factors such as STS Score (8% or higher) or other co-morbid conditions unrelated to aortic stenosis such as severe chronic obstructive pulmonary disease (COPD), chest deformities and irradiated mediastinum

4. NYHA Functional Class > II

5. Multidisciplinary heart team (cardiologist and cardiac surgeon) consensus that the transapical approach is the most suitable access route for TAVI due to the presence of the following anatomic conditions:

   • porcelain aorta or
   • severely calcified or highly tortuous peripheral vasculature not appropriate for transfemoral transcatheter aortic valve implantation or
   • vessels too small for retrograde approach or
   • other anatomical conditions making transapical approach more suitable

6. Aortic annulus diameter from ≥ 21mm up to ≤ 27mm by CT or TEE

7. Patient willing to participate in the study and provides signed informed consent

Exclusion Criteria:

1. Congenital unicuspid or bicuspid aortic valve or non-calcified
2. Extreme eccentricity of calcification
3. Severe mitral regurgitation (> Grade 3)
4. Pre-existing prosthetic heart valve in any position and / or prosthetic ring
5. LV apex is not accessible via transapical access due to severe chest deformity
6. Previous surgery of the LV using a patch, such as the Dor procedure
7. Presence of apical LV thrombus
8. Calcified pericardium
9. Septal hypertrophy unacceptable for transapical procedure
10. Transesophageal echocardiogram (TEE) is contraindicated
11. ECHO evidence of intracardiac mass, thrombus, or vegetation
12. LVEF < 20% by ECHO
13. Need for emergency intervention for any reason within 30 Days of scheduled procedure
14. Any percutaneous intervention, except for balloon valvuloplasty (BAV) within 1 month prior to implant procedure
15. Untreated clinically significant coronary artery disease requiring revascularization within 30 days before or after the study procedure
16. Acute myocardial infarction within 1 month prior to implant procedure
17. Previous TIA or stroke within 6 months prior to implant procedure
18. Active gastrointestinal (GI) bleeding within 3 months prior to implant procedure
19. Scheduled surgical or percutaneous procedure to be performed prior to 30 day visit
20. History of bleeding diathesis, coagulopathy, refusal of blood transfusions or severe anemia (Hb<8 g/dL)
21. Systolic pressure <80mmHg, cardiogenic shock, need for inotropic support or IABP
22. Primary hypertrophic obstructive cardiomyopathy (HOCM)
23. Active infection or endocarditis
24. Hepatic failure (> Child B)
25. Chronic renal dysfunction with serum creatinine > 3.0 mg/dL or renal dialysis
26. Neurological disease severely affecting ambulation, daily functioning, or dementia
27. Life expectancy < 12 months due to non-cardiac co-morbid conditions
28. Intolerance to aspirin, clopidogrel, contrast media, or porcine tissue and allergy to nickel
29. Pregnant or breast-feeding women
30. For other severe illnesses of the patient (e.g. active carcinoma), the investigator shall decide on an individual basis whether the patient is not to be included in the study
31. Currently participating in an investigational drug or another device study

The data and study protocol for this clinical trial may be made available to other researchers in accordance with the Boston Scientific Data Sharing Policy (http://www.bostonscientific.com/en-US/data-sharing-requests.html).