ICD-10 I46.9
Billable / Specific HCC v28: 84 MCCCardiac arrest, cause unspecified
About ICD-10-CM I46.9
ICD-10-CM code I46.9 represents Cardiac arrest, cause unspecified. This is a billable/specific code in the Circulatory System chapter (block I46). The 2026 edition of ICD-10-CM I46.9 became effective on October 1, 2025.
Coding Tips for I46.9
Specialist guidance from the PayerReady Medical Coding Team. Specificity warnings, HCC capture rules, sequencing notes.
I46.9 is a CMS-HCC v28 risk-adjustment code (category 84). To count for the patient Risk Adjustment Factor (RAF), document the diagnosis with MEAT language each calendar year: Monitored, Evaluated, Assessed, Treated. A diagnosis on the problem list alone does not satisfy CMS RADV audit standards. Include the diagnosis in the assessment with current status and current treatment plan.
I46.9 is designated MCC for MS-DRG grouping. On inpatient claims, this code can shift the DRG to the with-MCC variant when documented as a present-on-admission secondary diagnosis. Hospital CDI programs flag MCC opportunities during chart review. Failure to capture this code may leave 30 to 80 percent of the inpatient stay revenue unrealized.
Medicare Advantage HCC Impact
Capture this diagnosis annually for accurate risk adjustment. Missed HCC captures are the #1 revenue leak in Medicare Advantage risk programs.
Inpatient DRG Impact, MCC
codes Cardiac arrest, cause unspecified. As a Major Complication/Comorbidity (MCC), this can shift the DRG assignment to a higher-weighted category, substantial reimbursement impact.
Medicare LCD Coverage for I46.9
Local Coverage Determinations (LCDs) from CMS MACs that list I46.9 as a covered diagnosis.
Showing top 10 of 483 total . Click a CPT for full coverage scope.
Commercial Payer Coverage
Coverage policies from major commercial payers referencing I46.9.
1 Aetna
2 Cigna
5 Medicare
CPT Codes Commonly Billed with I46.9
Procedures frequently paired with this diagnosis based on PayerReady's Dx↔Px linkage data.
- 99285 High-level ER E/M — MI, cardiac arrest, respiratory failure, chest pain, syncope, head injury Emergency Medicine
- 99291 Critical care — cardiac arrest, respiratory failure, shock, anaphylaxis Emergency Medicine
- 99285 ED visit level 5 — STEMI, massive PE, respiratory failure, cardiogenic shock, cardiac arrest, ICH, encephalopathy, coma, anaphylaxis, SAH, ARDS, compartment syndrome Emergency Medicine
- G0448 CMS LCD: Billing and Coding: Implantable Automatic Defibrillators CMS LCD
- 33216 CMS LCD: Billing and Coding: Implantable Automatic Defibrillators CMS LCD
- 33230 CMS LCD: Billing and Coding: Implantable Automatic Defibrillators CMS LCD
- 33244 CMS LCD: Billing and Coding: Implantable Automatic Defibrillators CMS LCD
- 33264 CMS LCD: Billing and Coding: Implantable Automatic Defibrillators CMS LCD
- 33263 CMS LCD: Billing and Coding: Implantable Automatic Defibrillators CMS LCD
- 33220 CMS LCD: Billing and Coding: Implantable Automatic Defibrillators CMS LCD
Convert I46.9 to ICD-9-CM
Per CMS General Equivalence Mappings (GEMs), useful for legacy data review and historical claim analysis.
| ICD-10 | ICD-9 | Mapping Flags |
|---|---|---|
| I46.9 | 4275 | 10000 |
Flags format (5 digits): Approximate · No Map · Combination · Scenario · Choice List. Source: CMS 2017 GEMs (final version).
Codes Adjacent To I46.9
Other codes in section I30-I5A (Other forms of heart disease).
ICD-10 I46.9, Billing FAQ
Is ICD-10 code I46.9 billable? +
Yes, I46.9 is a billable ICD-10-CM code that can appear as a primary or secondary diagnosis on claims.
Does I46.9 affect Medicare Advantage HCC risk adjustment? +
Yes. I46.9 maps to CMS-HCC v28 category 84. Capture this diagnosis annually for accurate Medicare Advantage risk score.
Is I46.9 a CC or MCC for inpatient DRG? +
Yes, this code is designated as MCC. Documenting as a secondary diagnosis on inpatient claims can shift the DRG to a higher-weighted category.
What CPT codes are commonly billed with I46.9? +
Procedures frequently paired with I46.9 include: 99285, 99291, 99285, G0448, 33216.
What ICD-9 codes does I46.9 map to? +
Per CMS GEMs, I46.9 maps to ICD-9 codes: 4275. Useful for legacy data review and historical claim analysis.
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Reviewed by the PayerReady Medical Coding Team
Verified against the CMS 2026 code set on May 31, 2026.
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