Total-body 13N-NH3 PET/CT to Study the Blood Perfusion in Severe AS Patients Pre- and Post-TAVR in Whole Body

Inclusion Criteria: * Nine healthy volunteers with normal EF values * Patients with decreased cardiac function, while their heart function grading above II(New York Heart Association,NYHA) * Aged 60\~90 years old * Written informed consents will be offered and signed by all participants Exclusion Criteria: * History of vascular-related diseases in other organs * Severe liver and kidney dysfunctions * Patients who are pregnant or breast feeding * People under the age of 60 years old * Heart function grading below II(NYHA) * inability to lie or to maintain posture in the scanner for one hour