Transcatheter aortic valve replacement (TAVR) has a high risk and a high mortality rate in the treatment of aortic stenosis/regurgitation patients with cardiac insufficiency. The investigators aim to discuss the clinical efficacy of extracorporeal life support system(ECLS) during TAVR procedure in severe aortic lesion under very low ejection fraction (EF).

Transcatheter aortic valve replacement (TAVR), characterized by minimal invasion, no need for thoracotomy and extracorporeal circulation and definite mid- and long-term efficacy, has been recognized as an effective alternative replacing valve replacement through conventional thoracotomy for senile aortic valve stenosis. However, there are still a large number of patients whose left ventricular ejection fraction (LVEF) significantly declines due to the long history of disease and long-term heart injury, entering the decompensation stage. TAVR will still lead to such severe complications as intraoperative hemodynamic collapse and malignant arrhythmia in these patients, greatly increasing the mortality rate. It is pointed out in the American Heart Association Guideline (2017) that TAVR is not recommended as a treatment means for patients with very poor cardiac function under EF <20%. After conservative medication, the prognosis of patients with aortic valve stenosis under very low EF is poor with a 3-year mortality rate above 85%, and the prognosis after heart transplantation remains controversial. According to the pathological basis of patients and preoperative results of dobutamine test, the cardiac systolic function of some patients is expected to be significantly improved after removal of aortic valve stenosis. Therefore, applying extracorporeal life support system, such as extracorporeal membrane oxygenation (ECMO) or cardiopulmonary bypass (CPB） in the guarantee of cardiopulmonary function during perioperative period of TAVR is considered as the optimal surgical strategy for such patients.

Inclusion Criteria:

1. The age of patient is ≥50 yrs;
2. Severe aortic stenosis or regurgitation patients (The area of central regurgitation exceeds 40% of left ventricular area; regurgitant volume ≥10ml；EROA≤1.0cm2; PGmean≥50mmHg (Satisfy any condition).
3. Small incision surgery of chest can be tolerated.
4. General anesthesia is tolerable

4. The subject was informed of the clinical application nature of the technology and agreed to participate in all requirements of the clinical application of the new technology, signed the informed consent and agreed to complete.

Exclusion Criteria:

1. Subject who are pregnant, lactating or scheduled to pregnant during the period of the clinical new technology.
2. Subjects with active endocarditis or rheumatic mitral valve disease.
3. Life expectancy <1 year for cardiac or other malignant tumors.
4. Participate in other clinical trial.
5. In the judgment of the investigator, subjects had poor acceptance of chemotherapy, and they cannot complete the trial as required.