Well, if you have severe mitral regurgitation, your doctor is right . . . you should have the valve repaired or replaced before the dilation of the heart gets to the point where you have significant heart failure. I am not aware of valve replacement being a complete contraindication to diving . . . you might talk to the guys at Duke about that. There is nothing I can think of about being underwater or under pressure that should affect the performance of a prosthetic valve, but obviously, the sets of people who have had valve replacements and people who dive will have a very small intersection.