The National Space Biomedical Research Institute is interested in learning more about heart function in space. One potential problem with long duration, manned space flight is muscle loss- including loss of heart muscle. One goal of our research is to help identify why this muscle loss occurs. We are interested in patients undergoing aortic valve surgery because this procedure is performed to correct a problem with the valve that may also change heart function. This change in heart function may provide information that is useful in understanding and potentially preventing the loss of cardiac muscle in space.