CPT code 93657 – Additional ablation of atrial tissue during AF catheter ablation

Key Takeaways

CPT 93657 is a CPT add-on code (+), meaning it cannot be billed alone and always requires the primary code 93656 on the same claim.

93657 covers ablation of atrial tissue beyond pulmonary vein isolation, such as roof lines, mitral isthmus lines, or focal non-PV trigger sites.

The Medicare MUE for 93657 is 1 unit per session. Several additional lesion sets are reported as one unit, with each set documented in the operative note.

Pabau’s claims management software runs validation checks before each claim is sent, so details such as membership numbers and authorization codes are in place.

CPT Code 93657: Official descriptor and procedure overview

The American Medical Association (AMA) defines CPT Code 93657 as follows.

Additional linear or focal intracardiac catheter ablation of the left or right atrium for treatment of atrial fibrillation remaining after completion of pulmonary vein isolation

The descriptor closes with the add-on instruction (List separately in addition to code for primary procedure).

In plain terms, the electrophysiologist first isolates the pulmonary veins, the core of most AF ablation sessions. Sustained AF or demonstrable non-PV triggers may then require additional ablation work in the left or right atrium. That work, documented separately and performed at a distinct anatomical target, is what 93657 captures.

Common additional ablation targets covered by 93657 include:

• Roof line ablation connecting the superior pulmonary veins
• Mitral isthmus line connecting the left inferior pulmonary vein to the mitral annulus
• Posterior wall isolation beyond standard PVI
• Focal ablation of non-pulmonary vein triggers (e.g., left atrial appendage, superior vena cava, coronary sinus)

Cardiology billing teams can flag 93657 opportunities at charge capture with claims management software that carries the full CPT code set. Otherwise, the missed code tends to surface during a post-payment audit.

Add-on code status and eligible primary codes for 93657

CPT 93657 carries the add-on code designation (+) in the AMA codebook. That designation has two practical consequences. The code cannot be reported alone on a claim, and it is exempt from the multiple-procedure payment reduction rules that apply to base codes.

The AMA parenthetical instructions list one eligible primary code:

Reporting 93657 with any primary code other than 93656 (including a standalone E/M code) is incorrect per AMA guidelines. Claims submitted with 93657 paired to an ineligible primary will deny on edit before reaching the adjudication queue.

How many times can CPT 93657 be billed per session?

CPT 93657 is billed once per session. The Medicare medically unlikely edit (MUE) for 93657 is 1 unit, and CPT does not support reporting multiple units. When the electrophysiologist ablates several additional lesion sets beyond pulmonary vein isolation, they are reported as one unit of 93657. Each lesion set is still documented.

The documentation supporting that single unit must address all of the following for each additional ablation target:

• The anatomical site of the additional ablation (e.g., roof line vs. mitral isthmus line)
• The energy modality used (radiofrequency or cryoablation) and specific catheter used
• Electroanatomic mapping data confirming the target and lesion completeness
• Clinical rationale: why the additional ablation was necessary (e.g., persistent AF after PVI, documented non-PV trigger identified intraoperatively)
• Endpoint achieved (e.g., bidirectional conduction block across the line, trigger elimination)

Billing more than one unit of 93657 for a session exceeds the Medicare MUE and will deny. The operative report should still describe each lesion set on its own terms. A general statement that “additional ablation was performed” does not support the code.

Clinical procedure: What happens during a 93657 atrial fibrillation ablation

Understanding the clinical steps covered by 93657 helps coders confirm the operative report matches the code before submission.

After PVI is completed (reported under 93656), the electrophysiologist assesses whether AF terminates. If sustained AF continues or if electroanatomic mapping identifies non-PV triggers, additional ablation work begins, and that work is what 93657 captures. Typical steps:

1. Post-PVI assessment: The EP checks for AF inducibility and maps residual triggers using a 3D electroanatomic mapping system (CARTO, EnSite, or Rhythmia).
2. Target identification: The roof, mitral isthmus, posterior wall, or a focal trigger site is identified based on activation mapping or empiric anatomical approach.
3. Additional ablation: RF energy or cryoenergy is applied along the identified line or focal site. Catheter contact force and impedance are monitored throughout.
4. Endpoint verification: Bidirectional conduction block is confirmed across any linear lesion using differential pacing. Focal triggers are confirmed eliminated by repeat burst pacing.
5. Documentation: The EP documents the target, technique, energy delivered, and endpoint achieved in the procedure note before closing.

Per AAPC coding guidance, 93657 is only appropriate when the additional ablation is a clinically indicated extension of the procedure. Routine technique variation within the primary PVI does not qualify.

Documentation requirements to support a CPT 93657 claim

Documentation failures are the leading cause of 93657 denials. The operative or procedure note must contain each element below to withstand payer audit or pre-payment review.

• Primary procedure performed: Explicit statement that pulmonary vein isolation was completed (supporting the primary code 93656).
• Clinical rationale for additional ablation: Why additional work was performed, tied to a finding. Examples are sustained AF post-PVI, a specific trigger identified by mapping, or an evidence-based anatomical substrate approach per AHA/ACC guidelines.
• Specific ablation target(s): Anatomically precise language: “roof line connecting right superior and left superior PVs,” not “additional left atrial ablation.”
• Mapping data: Reference to the electroanatomic mapping system and the mapping findings that guided target selection.
• Energy type and catheter: RF or cryo, specific catheter model, contact force readings if available.
• Endpoint documentation: Confirmed bidirectional block, trigger elimination, or post-ablation rhythm outcome.
• Target-by-target specificity: When several additional lesion sets are performed, each target gets its own documentation block in the procedure note. They are still reported as one unit of 93657.

A clean claim for 93657 is built in the procedure room, not the billing office. The billing team’s job is to confirm the note contains these elements before submission, not to infer them from the diagnosis or general procedure description.

CPT 93657 vs 93656 vs 93655: Key differences and when to use each

Confusion among 93657, 93656, and 93655 is the most common coding error in EP billing. Each code has a distinct role.

The critical distinction between 93657 and 93655 is scope. 93657 applies to additional ablation within the AF substrate in the atria. 93655 applies to ablation of a separate, distinct arrhythmia focus or accessory pathway. Both can be added to 93656 (93655 also to 93653 and 93654), but they cannot be used interchangeably. Reporting 93655 for roof-line ablation is incorrect, just as reporting 93657 for AFL flutter isthmus ablation done as a separate clinical target is incorrect.

Medicare reimbursement for CPT 93657: Rates, RVUs, and payer policies

CPT 93657 is covered by Medicare for medically necessary AF catheter ablation. Because it is an add-on code, reimbursement is structured as a supplement to the primary code’s payment, not as a full standalone allowable.

Always verify current rates using the CMS Physician Fee Schedule lookup tool, as Medicare payment rates are updated each January. Locality-adjusted rates can vary significantly from the national average. The FastRVU lookup tool provides 2026 RVU values with locality multipliers for quick reference.

Submit 93657 claims as electronic claims via Claim.MD, Pabau’s US clearinghouse partner. It sends CMS-1500 claims to thousands of US payers and tracks each one through acceptance, payment, or denial. The clearinghouse also returns electronic remittance advice (ERA) with CARC denial codes when 93657 is rejected, making root-cause identification faster than paper EOBs.

Prior authorization requirements for CPT 93657

Prior authorization requirements for 93657 vary by payer and often follow the authorization granted for the primary AF ablation code (93656). Medicare fee-for-service does not require prior authorization for catheter ablation, but Medicare Advantage plans frequently do.

Major commercial payers with known prior authorization requirements for AF catheter ablation include:

• UnitedHealthcare: Prior auth required for AF ablation; the authorization typically covers the full procedure including planned add-on codes. Confirm 93657 is listed on the authorization request.
• Cigna (Evicore): Uses evicore.com clinical criteria for AF ablation. Medical necessity review required; AHA/ACC guideline criteria for appropriate use of catheter ablation must be met.
• Aetna: Requires prior authorization for AF ablation. Aetna’s clinical policy references ACC/AHA guidelines for class I and IIa indications.
• Medicare Advantage plans: Individual plan policies govern; check each plan’s portal before scheduling.

For all payers requiring prior auth, the authorization request should explicitly list 93657 alongside 93656. An authorization that covers only 93656 may result in automatic denial of 93657 at adjudication, even when the clinical work is supported. Robust insurance eligibility verification processes that capture authorization details at the time of scheduling reduce this risk significantly.

Medical necessity documentation for prior auth should reference the AHA/ACC guidelines for catheter ablation of AF. It should also state the indication: symptomatic AF refractory or intolerant to at least one Class I or III antiarrhythmic drug. Record left atrial size and ejection fraction as well.

Strong medical billing compliance practices require verifying authorization scope before the procedure, not after.

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Common denial reasons for CPT 93657 and NCCI bundling edits

93657 denials cluster around a small set of correctable errors. Understanding each one allows billing teams to address them systematically.

NCCI edits for 93657 are updated quarterly. The current edit file should be checked against the full procedure code list for each EP session, particularly when 93655 is also reported. Intracardiac echocardiography and 3D mapping have been bundled into 93656 and 93657 since 2022, so they are not reported separately. Modifier 59 or XU can override certain column 1/column 2 edits when documentation confirms a separate, distinct service. Never apply these modifiers without supporting operative note language. Effective denial management workflows track NCCI-related denials separately from medical necessity denials, since each requires a different appeal approach.

ICD-10 diagnosis codes supporting medical necessity for CPT 93657

Every 93657 claim must be paired with an appropriate ICD-10-CM diagnosis code establishing the AF indication. An unspecified code used when a more specific one is available is a frequent soft-denial trigger. It can also flag claims for medical necessity review.

Verify ICD-10-CM codes against the current fiscal year’s official code set via the CDC/NCHS ICD-10-CM web tool. The AF code set was reorganized in ICD-10-CM FY2020, effective October 1, 2019, when I48.11, I48.19, I48.20, and I48.21 were added. Some older codes are no longer valid. Using a retired code alongside 93657 will trigger a claim edit before adjudication and compound denial resolution time. Integrating your revenue cycle with revenue cycle management workflows that include ICD-10 code validation reduces this error category significantly.

Conclusion

CPT Code 93657 is a high-value add-on code that cardiology billing teams often under-report. The documentation audit tends to happen after the procedure rather than at the point of care. When the electrophysiologist documents each additional ablation target in real time, with anatomical precision and endpoint confirmation, 93657 is a clean, defensible claim.

Pabau’s claims management software checks that details such as membership numbers and authorization codes are in place before a claim is sent. It also posts ERA remittances, so EP billing teams see 93657 denials at the claim level. To see how Pabau handles cardiology billing workflows end to end, book a demo.

Continue your research

Need to understand how clearinghouse edits catch CPT errors before submission? Our Claim.MD clearinghouse guide explains how pre-submission validation works across 4,000+ US payers.

Want to reduce claim denials systematically across your billing operation? Denial codes in medical billing breaks down the CARC and RARC codes that appear on remittances and how to act on each one.

Exploring how a superbill supports complex EP procedure documentation? Our superbill guide covers what elements must be present to support add-on code claims like 93657.

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