By the way, doctor: Why is my mitral valve leaking?

Q. I had cardiac bypass surgery three years ago. I didn't have a heart attack; none of my heart muscle was killed. But about two months ago, a stress test showed that the mitral valve in my heart is leaking. What could have caused it, and what can I do about it?

A. The mitral valve controls blood flow from the left atrium (one of the two upper chambers of the heart) to the left ventricle, the strong lower chamber that pumps blood out of the heart and into the aorta.