Safety and Feasibility of TRISKELE in Severe AS

Inclusion Criteria: 1. Age ≥ 70 years old; 2. Patients with symptomatic severe aortic stenosis (echocardiographic mean pressure gradient across aortic valve ≥ 40mmhg, or blood flow velocity across aortic valve ≥ 4.0m/s, or aortic valve area \< 0.8cm2, or effective aortic valve area index \< 0.5cm2/m2); 3. Patients with biological valve decay meeting the criteria in (2) above; 4. NYHA grade ≥ grade II; 5. The life expectancy after artificial valve implantation is more than 1 year; 6. Patients who are anatomically suitable for transcatheter aortic valve implantation; 7. Two or more cardiothoracic surgeons evaluate and record it as surgical contraindication or as high-risk surgery and unsuitable for routine surgery; 8. Patients who can understand the purpose of the trial, voluntarily participate in and sign informed consent, and are willing to accept relevant examination and clinical follow-up. Exclusion Criteria: 1. Acute myocardial infarction occurred within 30 days before this treatment (WHO definition: Q-wave MI, or non-Q-wave MI with elevated creatine kinase isoenzyme and troponin T); 2. Patients whose aortic root anatomy and lesions are not suitable for artificial valve implantation; 3. Compound aortic valve disease (aortic stenosis with severe regurgitation); Severe mitral regurgitation; 4. Hematological malignancies, hemophilia and other coagulation disorders; 5. Hemodynamic instability, requiring mechanical cardiac assistance; 6. Emergency operation for any reason; 7. Obstructive hypertrophic cardiomyopathy; 8. Severe left ventricular dysfunction, left ventricular ejection fraction (LVEF) \< 30%; 9. Severe right ventricular dysfunction; 10. Echocardiography showed the presence of intracardiac mass, thrombus or vegetations; 11. Active peptic ulcer or upper gastrointestinal hemorrhage within 3 months; 12. Allergic to nickel titanium alloy, stainless steel alloy, PU (polyurethane), or contrast agent; Unable to tolerate anticoagulant and antiplatelet therapy; 13. Cerebrovascular events (CVA) occurred within 3 months, including ischemic stroke and hemorrhagic stroke, excluding transient ischemic attack (TIA); 14. Vascular diseases affecting the instrument approach; 15. Infective endocarditis in active phase or other active infections; 16. Those who have participated in clinical trials of other drugs or medical devices before enrollment and have not reached the time limit of the main research endpoint.