The purpose of this study is to conduct the initial clinical investigation of the Foldax Polymer Mitral Valve to collect evidence on the device's safety and performance. The study is anticipated to confirm successful clinical safety and clinical effectiveness with significant improvements in clinical hemodynamic performance.

The Foldax Polymer Mitral Valve is indicated as a replacement for a diseased, damaged, or malfunctioning native mitral heart valve via open heart surgery. This is a first in human study conducted under US FDA's Early Feasibility Investigational Device Exemption and will enroll up to 15 patients. These patients will be followed up to 5 years after implantation.

Inclusion Criteria:

• Is 18 years or older
• Is a candidate for mitral valve replacement with cardiopulmonary bypass
• Is a candidate for mitral valve replacement due to:
• Moderate to severe mitral valve stenosis,
• Moderate to severe mitral valve regurgitation, or
• Moderate to severe mixed mitral stenosis/regurgitation
• Able to withstand short term anticoagulation
• Willing and able to comply with protocol requirements

Exclusion Criteria:

• Prior mitral valve surgery for valve replacement or valve repair (this does NOT include percutaneous interventions i.e. Mitraclip, chordal replacement)
• Requires emergency surgery
• Requires other planned surgery within 12 months of valve replacement
• Active endocarditis or active myocarditis
• Acute preoperative neurological deficit defined as neurological deficit < 3 months prior to enrollment
• Non-cardiac illness resulting in a life expectancy of less than 12 months
• Enrolled in another investigational device or drug study (enrolled patients may not enroll in other studies)
• Myocardial infarction, or severe cardiac adverse event which has not returned to baseline for at least 30-days prior to enrollment
• Aortic aneurysm or other medical condition that creates a higher than usual risk of surgical complications
• Renal or hepatic failure
• Hematological disorders, patients must not have a hematocrit of <30%, hemoglobin <10 g/dL, platelet count of <100,000 cells/µL, or WBC <4,000 cells/µL; coagulation profile must not be outside of normal limits
• Patients who are prisoners or mentally ill
• Patients who are pregnant or expect to become pregnant in the 12 months following implantation, or are lactating
• Has a positive test result for COVID-19 virus (baseline or preoperative)
• Patients who have withdrawn after implantation may not re-enter
• Intraoperatively it is determined that the patient anatomy is not compatible with the device.