No, it's not fatal. I, myself, have mitral valve prolapse
) which basically means that my mitral valve is defective and allows blood to flow from the ventricle back into the atrium, which it's not supposed to do. This is pretty common and not fatal in the least. If your boyfriend only has a heart murmur
, then he's fine. His heart is merely skipping a beat or two--nothing to worry about, though you might want to see doctor just to get a professional opinion.