If I have an AutoCAD pat file can I import it into Revit?
Yes, you can do this and here is how:
Select from the Ribbon click Manage tab > Settings panel > Additional Settings > Fill Patterns.
The Fill Patterns dialog box will appear on screen, if you click on the New button in the top left hand side of the window.
Now you will see the New Pattern dialog box on screen. If you select Custom, it will give you the options to import an AutoCAD .pat file.