Failing surgical aortic bioprosthetic valve demonstrating = moderate stenosis and/or = moderate insufficiency;

Bioprosthetic surgical valve size suitable for SAPIEN X4 THV;

NYHA functional class = II;

Heart Team agrees the subject is at high or greater surgical risk;

The subject has been informed of the nature of the study, agrees to its provisions and has provided written informed consent;

Anatomical characteristics that would preclude safe femoral placement of the introducer sheath or safe passage of the delivery system;

Failing valve has moderate or severe paravalvular regurgitation;

Failing valve is unstable, rocking, or not structurally intact;

Known severe patient-prosthesis mismatch or bioprosthetic valve with residual mean gradient > 20 mmHg at the end of the index procedure for implantation of the original valve;

Increased risk of THV embolization;

Surgical or transcatheter valve in the mitral position;

Please contact study team for additional exclusion criteria;

• Aortic Valve Disease

• Aortic Valve Insufficiency

• Aortic Valve Stenosis

• Cardiovascular Diseases

• Heart Diseases

• Heart Valve Diseases

• SAPIEN X4

• Transcatheter aortic valve implantation (TAVI)

• Transcatheter aortic valve replacement (TAVR)

• Valve-in-valve

• Ventricular Outflow Obstruction

• Cardiology

• Edwards Lifesciences