New Pacemaker codes

Hi,
I have some questions regarding the new pacemaker codes- any help would be greatly appreciated...

The verbage on the 33212-33213 states ‘Insertion of pacemaker pulse generator only; with existing lead’
and the new codes (33227- 33228) differ because they include removal of an old generator and insertion of new.
The question is when would you ever have a situation where you don’t have an old generator to remove if there are existing leads?

The other question I had is- is there a CPT® code for repositioning of LV lead w/out generator insertion? Looks like 33225 includes insertion of generator…

Finally, what does it mean to ‘repair’ an electrode? (33218-33220) Is that common –I am sure our doctors replace or revise but don’t ‘repair’

Thank you.