Trifecta™ Durability Study

Inclusion Criteria: * Patients implanted for less than 9 months with a Trifecta™ valve, or patients who are candidates for implant with a Trifecta™ valve, as per current guidelines * Patient requires aortic valve replacement. * Patient is legal age in host country. * Patients must be able and willing to provide written informed consent to participate in this investigation * Patients must be willing and able to comply with all follow-up requirements Exclusion Criteria: * Patients with contraindication for cardiac surgery * Patients who are pregnant. * Patient is unwilling to or has an inability that reduces his mobility in order to attend the required follow-up visits. * Patient has active endocarditis * Patient has had an acute preoperative neurological event defined as patient has not returned to baseline 30 days prior to the planned valve implantation surgery. * Patient is undergoing renal dialysis. * Patient has a documented history of substance abuse within one year of enrollment or is currently a prison inmate. * Patient has a documented thrombus in left atrium or left ventricle. * Patient had in the past mitral or tricuspid valve replacement. * Patient needs mitral and/or tricuspid valve replacement. * Patient has an Ejection Fraction \< 25% * Patient had the Trifecta™ valve implanted as part of this study, but then had the device explanted * Preoperative evaluation indicates other significant cardiovascular abnormalities such as aortic dissection or ventricular aneurysm. * Patient has a life expectancy less than two years.