The research name of this project is: A prospective, multicenter and observational study on the safety and effectiveness of emergency transcatheter aortic valve replacement (TAVR) in the treatment of patients with severe aortic stenosis. It is a prospective, multi-center clinical study, and 35 cases are planned to be enrolled and followed up for 12 months (before discharge, 30 days, 6 months and 12 months). The research instruments used are VitaFlow Liberty® transcatheter aortic valve and recoverable delivery system. The purpose of this study is to evaluate the safety and effectiveness of emergency TAVR in patients with severe aortic stenosis. The main end point is the cumulative all-cause mortality 12 months after operation, and the secondary end points mainly include adverse cerebrovascular events (MACCE), acute renal injury, implantation rate of permanent pacemaker and valve function.

The research name of this project is: A prospective, multicenter and observational study on the safety and effectiveness of emergency transcatheter aortic valve replacement (TAVR) in the treatment of patients with severe aortic stenosis. The prognosis of patients with severe aortic stenosis (AS) is extremely poor in emergency, and the mortality of traditional balloon angioplasty (PBAV) is high. As a new treatment method, emergency TAVR needs multi-center data to verify its safety and effectiveness. Based on the preliminary results of a single center, this study was extended to multiple centers in China, aiming at providing high-level evidence, helping to optimize the implementation strategy of emergency TAVR, and promoting its wide application in patients with severe aortic stenosis, thus improving the clinical prognosis and quality of life of patients. This study is a prospective, multi-center clinical study, and 35 patients are planned to be enrolled. All participants are followed up before discharge, 30 days, 6 months and 12 months after valve implantation, and the research unit independently manages data, including data collection, collation and statistical analysis. The research instruments used are VitaFlow Liberty® transcatheter aortic valve and recoverable delivery system. The purpose of this study is to evaluate the safety and effectiveness of emergency TAVR in patients with severe aortic stenosis. The main end point is the cumulative all-cause mortality 12 months after operation, and the secondary end points mainly include adverse cerebrovascular events (MACCE), acute renal injury, implantation rate of permanent pacemaker and valve function. The selection criteria are: patients with severe aortic stenosis diagnosed by medical treatment; Meet one of the emergency TAVR indications (shock, persistent ventricular tachycardia or ventricular fibrillation, unstable angina pectoris or chronic heart failure requiring mechanical circulatory assistance devices, etc.); Voluntary participation and signing of informed consent. The main exclusion criteria are: aortic root anatomy and lesions are not suitable for artificial valve implantation; Anatomical morphology or vascular diseases that affect the instrument approach; Left ventricular outflow tract obstruction; Primary dilated cardiomyopathy; Thrombosis in left ventricle; Patients who cannot receive anticoagulant or antiplatelet therapy, etc. The statistical methods used are descriptive analysis, Kaplan-Meier survival analysis and Cox proportional hazard model (SAS 9.4). Following the Helsinki Declaration, China's Quality Management Standard for Clinical Trials of Medical Devices and ISO 14155:2011, all patients signed informed consent forms with the approval of the Ethics Committee.

Inclusion Criteria:

1. Patients with severe aortic stenosis diagnosed at the clinic: peak transvalvular flow velocity ≥4.0m/s, or mean transvalvular pressure difference ≥40mmHg(1 mmHg=0.133kPa), or aortic valve orifice area < <0.8cm2 (or effective aortic valve orifice area index < 0.5 cm2/m2);
2. Meet one of the following emergent TAVR indications:

1) Shock; 2) Combined with persistent ventricular tachycardia or ventricular fibrillation; 3) Difficulty in improving unstable angina pectoris or chronic heart failure requiring mechanical circulatory assistance with drugs; 4) Cardiopulmonary resuscitation is required for cardiac arrest; 3. Patients who can understand the purpose of the study, voluntarily participate in and sign the informed consent form, and are willing to accept the relevant examinations and clinical follow-up.

Exclusion Criteria:

1. Aortic root anatomy and lesions are not suitable for prosthetic valve implantation;
2. Anatomic morphology or vascular diseases affecting the instrument approach;
3. Left ventricular outflow tract obstruction;
4. Primary dilated cardiomyopathy;
5. Thrombus in the left ventricle;
6. Patients who are unable to receive anticoagulation or antiplatelet therapy;
7. Allergy to or resistance to Nitinol;
8. Active stage of infective endocarditis or other infection that the researcher believes affects the operation;
9. Severe disability senile dementia;
10. Patients with a life expectancy of less than half a year;
11. The investigator determined that the patient or family had poor compliance or declined to complete the study as required.

1. Severe aortic stenosis 2, high risk of surgery, or surgical taboo, is not suitable for conventional surgery valve replacement; 3, anatomically suitable for TAVI/TAVR