Transcatheter aortic valve implantation (TAVI) is well established, and can improve clinical outcomes of patients with severe aortic valve stenosis (AS) who are inoperable or have high surgical risk. Although the rates of periprocedural bleeding events are lower in TAVI compared to those in surgical aortic valve replacement, those in TAVI still remains high. In addition, current guideline recommended the dual antiplatelet (DAPT), clopidogrel plus aspirin, for a 3- to 6-month period after TAVI, however no evidences supports this approach. The antithrombotic regimen in patients undergoing TAVI is needed to be established.

To establish the antithrombotic regimen in patients undergoing TAVI,

1. the investigators assess the changes in platelet thrombus formation and white thrombus formation in patients undergoing TAVI measured by Total Thrombus Formation Analysis System (T-TAS).
2. the investigators analyze plasma microRNAs, and shear stress by using computational fluid dynamics (CFD) to clarify the mechanistic factors regarding those changes.

Inclusion Criteria:

• twenty years and older
• with the informed consent of the patient or support person in case of disability at baseline (patient intubated and ventilated)

Exclusion Criteria:

• withdrawn the informed consent
• patients with trans-apical approach
• critical illness condition (severe infectious disease, cancer, severe bleeding disorder)
• transition to the surgical AVR

Patients with severe symptomatic aortic valve stenosis, undergoing transcatheter aortic valve implantation