Read indexes of a SysHeader32 control

I've tried using
 

_GUICtrlHeader_GetItemText("[CLASS:SysHeader32; INSTANCE:1]", 0)

on a windows app, but it keeps returning an empty string. There should be at least 8 indexes to read from. I've tried 0-3 without any luck. Any ideas?

Note: the application window's class is WindowsForms10.Window.8.app.0.33c0d9d if that means anything. This is being done on an XP machine.