Handling hotkeys with modifiers

Question

I'm using RegisterHotKey to modify certain key combinations. For example, I want to replace Alt+Q with 'A' - I do this by simply registering Alt+Q hotkey and handling it by sending 'A'-up/'A'-down with SendInput. But Alt is still held down, so the target window receives Alt+A. How do programs such as AutoHotkey handle it, do they send an Alt-up every time an Alt+key is handled?