On-X Heart Valve - 17mm Aortic and 23mm Mitral

The purpose of the study is to assess the safety and efficacy of the 17mm On-X Aortic Prosthetic Heart Valve and the 23mm On-X Mitral Prosthetic Heart Valve when used to replace diseased aortic or mitral valves in human subjects. The On-X 17mm aortic valve will be implanted in approximately 20 and at least 15 patients who will be followed for at least 1 year. Patients will be any age and will require this size valve as determined in surgery but will be recruited prior to surgery based on results of preoperative screening tests. Enrollment into the 23mm mitral arm of the study has been terminated.