Cardiology Conundrum re FFR (Fractional Flow Reserve) CPT® 93571

Does anyone know the correct way to code the following for Physician B's portion:

Physician A performs a heart cath (CPT® 93458) and then calls in an interventional cardiologist (Physician B - from same practice) who only performs the FFR (CPT® 93571).

CPT® 93571 is an add-on procedure code and therefore cannot be billed without the 93458 in this instance, but since physician B did not do anything except the 93571 how should it be reported so that it does not get denied for being an add-on code without a primary code?

I am unsure if the 93458 should be reported again by Physician B with either no charge or perhaps a modifier?