The purpose of this study is to compare sizing,implant techniques, and hemodynamics between the Mitroflow Pericardial Aortic Valve and the Edwards Magna Heart Valve.

Comparisons of valve types are often made according to labeled valve sizes. There is growing evidence that in the majority of cases the actual sizer and valve dimensions vary from the labeled diameters, which may not be related to any hemodynamically meaningful dimension. The disagreement between the true valve dimensions and the labeled valve size may render comparisons based on labeled size meaningless

Inclusion Criteria:

• Patients who are indicated for implant with a bioprosthetic valve in the aortic position according to the current practice for valve selection at the center.

Exclusion Criteria:

• Less than 18 years of age
• Emergency Surgery
• Pre-existing valve prothesis in the aortic position
• Aortic root replacements or enlargements
• Active endocarditis