Ask Dr. Z

I know that we are to code only one base intervention per main vessel, and then up to two branch interventions off a base. However, I'm not sure if I can code two interventions here. A DES was placed in the mid RCA (C9600-RC) for an 80% stenosis, and then there was a 70% stenosis in the distal RCA extending into the PDA. A stent was placed in the distal RCA and covered and extended into the PDA portion of the stenosis. It looks like it was a contiguous lesion. So would the stent extending into the PDA not be coded since the lesion started in the main RCA? Or since it extended into the PDA, would that count as a branch intervention and be coded C9601-RC?