I do billing for an IDTF. We send a sonographer into the PCP's office to do stress echo's. The results are read by our cardiologist & reported back to the PCP. We bill 93351, 93321 & 93325. The cardiologist is not on site but the PCP is. I am concerned about the physician supervision on this. Are we correct in billing the 93351 when it is not our Doctor doing the supervising? Should we be billing 93350 instead? Also what can the PCP bill for?