Do you know why Visual Studio doesn't work for Qt variables or classes?
No, and I cannot make an educated guess because "doesn't work" and "wrong values" is not a good description of what you are seeing.

The first thing to check is that your project is built with debugging symbols.

Many (most) Qt classes are built with a private implementation so often the only member variable of a class is a pointer to a private class and that's all you see by default. Debuggers use helper code to present user friendly versions of these objects (like GDB in the Qt SDK does). As a non-Visual Studio user I don't know what helpers are available.