CPT code 33500 represents an open cardiac surgical procedure performed on cardiopulmonary bypass to close a fistula, either via an external approach or from within a cardiac chamber. As a component of complex cardiac surgical care, this code captures definitive repair of abnormal intracardiac or extracardiac communications that can cause hemodynamic instability, heart failure, or embolic risk. Nationally, accurate use of this code matters for clinical documentation, perioperative resource planning, and alignment of surgical quality metrics.

Key payers in this analysis include Aetna, Blue Cross Blue Shield, Cigna Health, UnitedHealthcare, and Medicare. Readers will find a concise overview of the code’s clinical context, typical site of service, and the types of information used in payer evaluations. The publication outlines common billing modifiers and related administrative considerations where available, and summarizes what is known about coding practice and reimbursement frameworks for major commercial payers and Medicare. It highlights the clinical scenarios that generate use of CPT code 33500, and provides a clear reference for clinicians, coding staff, and policy analysts seeking to understand how this procedure is classified and reported.