This trial is designed to confirm the clinical safety and effectiveness of the Trifecta valve by establishing associated adverse event rates, clinical status as indicated by New York Heart Association (NYHA) functional classification, hemodynamic performance, and hematology analysis.

The clinical investigation is a multi-center, multi-country, prospective, non-randomized, observational study without concurrent or matched controls, designed to evaluate the safety and effectiveness of the Trifecta valve. A maximum of 120 subjects requiring aortic valve replacement will be implanted at a maximum of 6 investigational sites in Europe. The sample size is based on late patient-years of follow-up with a minimum of 400 late patient-years experience required.

Inclusion Criteria:

1. Patient requires aortic valve replacement. (Note: patients undergoing concomitant procedures, e.g. coronary artery bypass grafting, or valve repair, are eligible for this study).
2. Patient is legal age in host country.
3. Patient (or legal guardian) has given written informed consent for participation prior to surgery.
4. Patient is willing to undergo all study procedures and adhere to data collection and follow-up requirements.

Exclusion Criteria:

1. Patient is pregnant or nursing (women of child bearing potential must have a documented negative pregnancy test within one week prior to surgery).
2. Patient already has a prosthetic valve(s) at a site other than the aortic valve.
3. Patient requires concomitant replacement of the tricuspid, pulmonary, or mitral valve.
4. Patient has an inability or is unwilling to return for the required follow-up visits.
5. Patient has active endocarditis (patients with previous endocarditis must have two documented negative blood culture results prior to enrollment).
6. Patient has had an acute preoperative neurological event defined as patient has not returned to baseline or has not stabilized 30 days prior to the planned valve implantation surgery.
7. Patient is undergoing renal dialysis.
8. Patient has a documented history of substance abuse within one year of enrollment or is currently a prison inmate.
9. Patient is currently participating in the study of an investigational drug or device, or the patient was previously participating in an investigational drug study and has not completed a 30-day wash out period.
10. Patient had the Trifecta valve implanted as part of this study, but then had the device explanted.
11. Preoperative evaluation indicates other significant cardiovascular abnormalities such as aortic dissection or ventricular aneurysm.
12. Patient has a life expectancy less than two years.