A patient comes in through ED as STEMI. Straight to CCL, LAD is the culprit vessel. DES placed, C9606. After LAD is stented and flow restored, an ostial diagonal lesion is found resulting in DES to the diagonal. The question is: Is the diagonal DES coded as C9601- DES Additional Vessel, since it was treated in the same manner as the STEMI LAD? Or is it coded C9600 because even though DES, it was not a STEMI vessel like the primary vessel C9606?