Microvolt T-Wave Alternans (MTWA) — NCD 310 | CMS Coverage Update

TL;DR: The Centers for Medicare & Medicaid Services modified NCD 310 governing Microvolt T-Wave Alternans (MTWA) testing, with a policy review date of January 9, 2026. Here's what billing teams need to know about coverage criteria, MAC-level flexibility, and documentation requirements.

This CMS MTWA coverage policy has been in place since 2006, but the January 2026 review confirms the current structure: spectral analysis (SA) method testing carries national coverage, while all other methods fall under local coverage determination by Medicare Administrative Contractors. The policy does not list specific CPT or HCPCS codes. Your billing team needs to understand how this split-coverage structure affects claim submission and what MAC jurisdiction controls before billing non-SA MTWA.

Quick-Reference Table

CMS Microvolt T-Wave Alternans Coverage Criteria and Medical Necessity Requirements 2026

NCD 310 is the National Coverage Determination governing Medicare coverage of Microvolt T-Wave Alternans testing. It splits coverage based on the testing method used — and that split has real billing consequences.

The nationally covered indication is specific: MTWA diagnostic testing for evaluation of patients at risk for sudden cardiac death (SCD), using the spectral analysis (SA) method only. This coverage has been in effect since March 21, 2006. If your practice uses SA-method MTWA and documents the appropriate medical necessity criteria, you have national Medicare coverage to rely on.

The medical necessity case for MTWA testing centers on SCD risk stratification. Specifically, CMS recognizes MTWA's role in identifying patients who may be candidates for implantable cardioverter defibrillator (ICD) therapy — and, critically, identifying lower-risk patients unlikely to benefit from ICD placement. A negative MTWA result can be clinically meaningful precisely because it may support a decision not to implant an ICD. Document that clinical context clearly in the medical record.

The SA method requires specialized proprietary electrodes. Software performs spectral analysis on the minute T-wave voltage changes and produces a report for physician interpretation. If your documentation doesn't clearly indicate the SA method was used, you're creating a gap that will invite a claim denial. Be explicit in the procedure notes.

The Modified Moving Average (MMA) method — which uses standard ambulatory ECG equipment and assesses T-wave alternans as a continuous variable — does not carry national coverage under NCD 310. CMS has not declared it non-covered nationally, but it has also not covered it nationally. Coverage for MMA-method MTWA falls entirely to your MAC under local coverage determination authority, effective January 21, 2015.

The coverage policy does not mention prior authorization requirements at the national level. However, your MAC's local coverage determination for non-SA methods may impose prior authorization or documentation thresholds. Check your MAC's LCD directly before assuming clean claims for MMA-method testing.

CMS MTWA Exclusions and Non-Covered Indications

There are no nationally non-covered indications listed under NCD 310. CMS left section C blank — no categorical exclusions exist at the national level.

That said, this isn't a free pass. The absence of a national non-covered designation for non-SA methods doesn't mean those claims will pay. It means your MAC decides. That's a meaningful distinction in revenue cycle terms: a national non-coverage designation is a hard wall, but MAC-level discretion means your reimbursement depends entirely on which MAC jurisdiction you're in and what LCD they've published.

If you bill in multiple MAC jurisdictions, this creates real inconsistency in your revenue expectations for non-SA MTWA testing. Two practices doing identical testing could get opposite coverage determinations based purely on geography.

Coverage Indications at a Glance

CMS MTWA Billing Guidelines and Action Items 2026

The January 9, 2026 review of NCD 310 didn't rewrite the rules — it confirmed them. That confirmation matters because it signals CMS isn't moving toward broader national coverage for non-SA methods anytime soon. Plan accordingly.

Here are the specific actions your billing team should take now:

If you're billing across multiple MAC jurisdictions, talk to your compliance officer before assuming uniform coverage for non-SA methods. The geographic variability here is real, and the financial exposure from denials across multiple sites adds up quickly.

CPT, HCPCS, and ICD-10 Codes for MTWA Testing Under NCD 310

The real policy data for NCD 310 does not list specific CPT, HCPCS, or ICD-10 codes. This is a known gap in the NCD as written, and it creates a practical billing challenge.

What this means for your team: Code selection for MTWA billing is not standardized at the national level through this NCD. Your billing team must obtain applicable codes from your MAC's local coverage determination or billing guidelines. Submit to your MAC directly if no LCD is available for your jurisdiction.

Where to Find the Applicable Codes

Do not assign codes to MTWA claims based on general ECG or cardiac monitoring codes without confirming they're appropriate for MTWA under your MAC's guidance. Incorrect code assignment drives both underpayment and claim denial risk.