Open and Thoracoscopic Approaches to Treat Atrial Fibrillation and Atrial Flutter (Maze and Related Procedures)
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Defines medical necessity, coverage stance, and prior authorization requirements for open and thoracoscopic maze and related procedures to treat symptomatic atrial fibrillation or atrial flutter for Medicare Advantage and Commercial products.
No material clinical or coverage changes in this revision.
Coverage Criteria for Maze and Related Procedures
Maze/modified maze during cardiac surgery
Covered when ALL of the following are met
Applies to CPT 33256, 33257, 33259
Procedures considered not covered / not medically necessary
Not covered / Not medically necessary when ANY of the following apply
CPT 33254, 33255, 33258
CPT 33265, 33266
Not covered
Hybrid ablation evidence summary
Summary of evidence and coverage stance for hybrid thoracoscopic and endocardial ablation:
Evidence shows increased AF-free survival and reduced cardioversion but higher periprocedural adverse events; largest RCT (CEASE-AF) reported composite major complications at 1 year of 9% vs 6% (hybrid vs standard); overall evidence insufficient to determine net health benefit
Stand-alone minimally invasive, off-pump maze procedures (including mini-thoracotomy approaches), hybrid ablation (combined percutaneous and thoracoscopic techniques), and open maze or modified maze procedures performed on a non-beating heart during cardiopulmonary bypass without concomitant cardiac surgery are excluded from coverage for the treatment of atrial fibrillation or flutter.
Procedures coded with CPT codes listed as not covered in this policy are excluded from coverage and are considered not medically necessary for Medicare Advantage Plans and Commercial Products when performed for atrial fibrillation or flutter. Billing these codes may result in claim denial.
Procedure Coding and Coverage Status
| 33256 | Maze or modified maze procedure (on non-beating heart during cardiopulmonary bypass) — considered medically necessary with concomitant cardiac surgery |
| 33257 | Maze or modified maze procedure (on non-beating heart during cardiopulmonary bypass) — considered medically necessary with concomitant cardiac surgery |
| 33259 | Maze or modified maze procedure (on non-beating heart during cardiopulmonary bypass) — considered medically necessary with concomitant cardiac surgery |
| 33256 | Operative tissue ablation and reconstruction of atria, extensive (eg, maze procedure); with cardiopulmonary bypass |
| 33257 | Operative tissue ablation and reconstruction of atria, performed at the time of other cardiac procedure(s), limited (eg, modified maze procedure) (List separately in addition to code for primary procedure) |
| 33259 | Operative tissue ablation and reconstruction of atria, performed at the time of other cardiac procedure(s), extensive (eg, maze procedure), with cardiopulmonary bypass (List separately in addition to code for primary procedure) |
| 33254 | Operative tissue ablation and reconstruction of atria, limited (eg, modified maze procedure) |
| 33255 | Operative tissue ablation and reconstruction of atria, extensive (eg, maze procedure); without cardiopulmonary bypass |
| 33258 | Operative tissue ablation and reconstruction of atria, performed at the time of other cardiac procedure(s), extensive (eg, maze procedure), without cardiopulmonary bypass (List separately in addition to code for primary procedure) |
| 33265 | Endoscopy, surgical; operative tissue ablation and reconstruction of atria, limited (eg, modified maze procedure), without cardiopulmonary bypass |
| 33266 | Endoscopy, surgical; operative tissue ablation and reconstruction of atria, extensive (eg, maze procedure), without cardiopulmonary bypass |
Provider Responsibilities and Authorization Requirements
Follow related prior authorization policy
Services described in this policy may also be subject to the payer's separate Prior Authorization of Services, Treatments or Procedures policy; follow that related policy for authorization requirements.
Placement in treatment pathway: catheter ablation and surgical alternatives
Percutaneous catheter (endocardial) ablation is an accepted second-line treatment after medication failure and may be used as first-line in some patients; surgical ablation (open or thoracoscopic) is an alternative approach to percutaneous catheter ablation.
Step therapy: none specified
This policy does not specify any step therapy requirements.
Document criteria for prior authorization and medical necessity (33256/33257/33259)
For prior authorization and medical necessity determinations for CPT codes 33256, 33257, and 33259, document that the maze or modified maze procedure was performed on a non‑beating heart during cardiopulmonary bypass with concomitant cardiac surgery and that the procedure was for symptomatic atrial fibrillation or flutter.
- Evidence that procedure was performed on a non‑beating heart during cardiopulmonary bypass with concomitant cardiac surgery
- Indication of symptomatic atrial fibrillation or flutter
Verify benefits and eligibility before scheduling
Verify member benefits and eligibility with the provider call center; coverage is governed by the member's subscriber agreement and/or employer agreement, which supersede this policy.
Denial risk: non‑covered standalone or hybrid procedures
Billing or requesting coverage for stand‑alone minimally invasive off‑pump maze procedures, hybrid ablation, or open maze/modified maze performed without concomitant cardiac surgery may result in denial because these procedures are not covered or are not medically necessary for AF/flutter.
- Stand‑alone minimally invasive, off‑pump maze procedures (including mini‑thoracotomy)
- Hybrid ablation (combined percutaneous and thoracoscopic approach)
- Open maze or modified maze performed without concomitant cardiac surgery
Background and Evidence Summary
Atrial fibrillation is a supraventricular tachyarrhythmia driven by focal triggering events (commonly originating from the pulmonary veins) and a susceptible atrial substrate that sustains disorganized electrical activity. First-line therapy typically involves medical management for rate or rhythm control; catheter ablation is an accepted second-line treatment after medication failure and may be considered earlier in selected patients. Surgical approaches (open or thoracoscopic maze and modified maze procedures) are alternative strategies designed to interrupt abnormal atrial conduction and restore sinus rhythm, and are most commonly performed concomitantly with other cardiac surgery procedures when done on a non-beating heart.
inv-03: Hybrid ablation evidence summary (also relevant to background)
Summary of trials, outcomes, and relevance to coverage decisions for hybrid and stand-alone procedures:
Largest RCT (CEASE-AF) found 9% vs 6% composite major complications at 1 year (hybrid vs standard)
Contributes to insufficient evidence of net health outcome improvement
See CPT codes 33254, 33255, 33258, 33265, 33266
Definitions
Revision History
Policy published (Provider Update) in May 2026.
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