CPT code 36221 covers the imaging supervision and interpretation portion of angiography conducted by catheterization through a distal artery into the thoracic aorta, with contrast injection to visualize arterial anatomy and detect vascular disease. Nationally, this code matters because it delineates the physician professional component for angiographic imaging distinct from technical or catheterization-only services, affecting billing, coverage determinations, and claims processing across payers. Key payers included in this analysis are Aetna, Blue Cross Blue Shield, Cigna Health, UnitedHealthcare, and Medicare. Readers will find a concise explanation of the clinical and billing context for CPT code 36221, an overview of payer coverage patterns and common modifiers used with this code, and practical benchmarks for claims adjudication and documentation expectations. The publication also outlines typical sites of service and the procedural scope that this code represents. Data not available in the input is noted where relevant.