This is a pre-market clinical investigation aiming to evaluate the safety and effectiveness of Microport™ CardioFlow VitaFlow™ II Transcatheter Aortic Valve System for the treatment of severe aortic stenosis.

This a prospective, multi-center, single-arm, objective performance clinical investigation, aiming to evaluate the safety and effectiveness of Microport™ CardioFlow VitaFlow™ II Transcatheter Aortic Valve System for the treatment of severe aortic stenosis. A total of 145 subjects will be enrolled in 18 clinical centers within China. Clinical or telephone follow-up is scheduled at 30 days, 6 months, 12 months, and 2-5 years after valve implantation.

Inclusion Criteria:

1. Age≥70 years;
2. Symptomatic , severe, aortic valve stenosis : peak velocity ≥4.0m/s, or mean transvalvular gradient ≥40mmHg(1 mmHg=0.133kPa), or effective orifice area<0.8cm² (or EOA index<0.5cm²/m²);
3. NYHA≥II class;
4. Estimated life-expectancy>12 months after implantation of the prosthetic valve;
5. Anatomically suitable for the transcatheter aortic valve implantation procedure;
6. The patients considered to high-risk or not suitable for surgical aortic valve replacement (SAVR), as assessed by two or above heart surgeons; The patient has been informed of the nature of the study, is willing to enroll in the study by signing a patient informed consent and agreeing to the scheduled follow up requirement.

Exclusion Criteria:

1. Acute myocardial infarction (MI) in last 30 days before the treatment;
2. Aortic root anatomy not suitable for the implantation of the transcatheter aortic valve；
3. Complicated lesion of the aortic valve (aortic stenosis with severe regurgitation); moderate-severe mitral valve stenosis; severe mitral valve regurgitation; severe tricuspid valve regurgitation;
4. Previous implantation of heart valve at any position；
5. Hemodynamic instability requiring mechanical hemodynamic support devices;
6. Need for emergency surgery for any reason;
7. Hypertrophic cardiomyopathy with obstruction;
8. Severe left ventricular dysfunction with left ventricular ejection fraction (LVEF) < 20%;Severe right ventricular dysfunction;
9. Active peptic ulcer or upper gastro-intestinal bleeding within the past 3 months;
10. Known hypersensitivity or contraindication to all anticoagulation/antiplatelet regimens, to nitinol, contrast media or other relevant elements.
11. Congenital aortic valve stenosis or unicuspid aortic valve;
12. Vascular diseases or anatomical condition preventing the device access;
13. Active endocarditis or other active infections at the time of treatment;
14. Participating in another trial and the primary endpoint is not achieved.
15. Inability to comply with the clinical investigation follow-up or other requirements.