Cardio Vascular Stress Tests

We are Primary Care physicians & our Dr's order Stress Tests on our Medicare patients.

We use CPT® code 78452, 93015, A9500 & A9505.

I have problems with Medicare paying on A9505. The dx codes are correct. Is there somthing that I am missing, does this code need a modifier? Not sure if we can use a modifier with an "A" code. Or it is just that Medicare does not pay on A9505? There is an LCD for A9505.

Any insight on this is welcome. Thank you in advance for your help.