Prospective Randomized On-X Versus SJM Evaluation Trial

The study is a multi-centre, randomized trial that will sequentially enroll up to 500
eligible patients in each group from up to 10 participating study centres internationally to
test the hypothesis.

Inclusion Criteria:

1. The patient requires an isolated mitral or isolated aortic valve replacement.
(Patients undergoing coronary artery bypass and / or concomitant repair of mitral or
tricuspid valves are eligible.)

2. The patient is a candidate for receipt of a mechanical heart valve.

3. The patient (or legal guardian) has signed a study-specific informed consent form
agreeing to the randomization, data collection and follow-up requirements.

4. The patient can be having a re-operative procedure, so long as the previous prosthetic
valve is explanted and the patient does not become a double valve implantation
patient.

Exclusion Criteria:

1. The patient is not a candidate to receive a mechanical heart valve.

2. The patient already has a prosthetic valve other than the valve(s) being replaced at
this time.

3. The patient requires a tricuspid valve replacement.

4. The patient is enrolled in another investigative study or trial.