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Answer: First of all review the operative report to identify the access site. Most likely the access site was in one of the lower extremities (such as common femoral artery.)
Regardless you should code any access site other than the upper-right extremity (brachial) or a direct carotid puncture (very rare) the same.
Typically a cardiologist places the catheter selectively into the common carotid on both sides (left and right) from a lower-extremity access site.
If this is the case you should report the right common carotid catheterization as 36216-RT (Selective catheter placement arterial system; initial second-order thoracic or brachiocephalic branch within a vascular family; right side) and the left common carotid catheterization as 36215-LT (Selective catheter placement arterial system; each first-order thoracic or brachiocephalic branch within a vascular family; left side).
Also you should check the report for what areas the cardiologist actually imaged. Typically you'll see that the cardiologist imaged the common internal and external carotids on both sides. In these situations you can bill both the cerebral (75671 Angiography carotid cerebral bilateral radiological supervision and interpretation) and cervical imaging codes (75680 Angiography carotid cervical bilateral radiological supervision and interpretation) for the same study.
Note: You should not however report the code for the external carotid imaging (75662 Angiography external carotid bilateral selective radiological supervision and interpretation) because this procedure requires selective catheter placement in the external carotid which is a very rare occurrence. "