Is mitral regurgitation the same thing as?mitral stenosis?

Not exactly: Mitral regurgitation (mitral valve regurgitation, mitral incompetence, mitral insufficiency) is leakage of blood backward through the mitral valve each time the left ventricle contracts.

Different issues: Mitral stenosis: essentially means the valve doesn't open all the way, the valve in narrow or narrowed... Mitral regurgitation: means the valve leaks when it is closed.