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ICD-10-CM I46.8: Cardiac arrest due to other underlying condition

I46.8 is the billable ICD-10-CM code for cardiac arrest due to other underlying condition, in category I46 (Cardiac arrest) of the Other forms of heart disease section. As a principal diagnosis it groups to MS-DRG 296 Cardiac Arrest, Unexplained with MCC, MS-DRG 297 Cardiac Arrest, Unexplained with CC, MS-DRG 298 Cardiac Arrest, Unexplained without CC/MCC (MDC 05 MDC 05: Diseases and Disorders of the Circulatory System); or MS-DRG 791 Prematurity with Major Problems, MS-DRG 793 Full Term Neonate with Major Problems (MDC 15 MDC 15: Newborns and Other Neonates with Conditions Originating in Perinatal Period). It maps to HCC 213 (Cardio-Respiratory Failure and Shock) in CMS-HCC V28. As a secondary diagnosis it is an MCC, excluded with 25 principal diagnoses. 26 LCD billing and coding articles list it as covered.

Compiled from CMS files by the QuickIntell RCM Editorial Team · Data effective · Method: reference methodology · Report a data correction

Data currency: ICD-10-CM code descriptions: FY2027 (effective October 1, 2026); IPPS Table 5 (MS-DRG weights): v44 FY2027 (final rule + CN3) (effective October 1, 2026); ICD-10-CM to HCC mapping: PY2027 initial ICD-10-CM mappings (dates of service 2026) (payment year 2027); Medicare Coverage Database billing and coding articles: MCD release October 8, 2026 (effective October 4, 2026). Next CMS release: FY2028 code files, effective October 1, 2027 for the ICD-10-CM code descriptions; FY2028 final rule (August 2027), effective October 1, 2027; an April 1 interim grouper update when CMS issues one for the IPPS Table 5 (MS-DRG weights); PY2028 advance notice (February 2027) and the PY2027 midyear final mapping (spring 2027) for the ICD-10-CM to HCC mapping; weekly, every Thursday for the Medicare Coverage Database billing and coding articles.

Code
I46.8
billable FY2027 ICD-10-CM code
Category
I46 Cardiac arrest
Chapter
9: Diseases of the circulatory system (I00-I99)
CC/MCC (MS-DRG v44)
MCC
CMS-HCC V28
HCC 213
POA reporting
Required

Tabular list notes for I46.8

The tabular list has no notes on I46.8 itself; the notes below apply from its parent headings.

Inherited from I46 (Cardiac arrest)

Excludes2 (not part of this condition, may be coded together)
  • cardiogenic shock (R57.0)

MS-DRG grouping when I46.8 is the principal diagnosis

MS-DRG v44 groups for I46.8 as principal diagnosis
MDCMS-DRGs
05 MDC 05: Diseases and Disorders of the Circulatory System296297298
15 MDC 15: Newborns and Other Neonates with Conditions Originating in Perinatal Period791793

The final group also depends on procedures, secondary diagnoses and discharge status; the MS-DRG lookup for I46.8 shows the full grouping logic.

CC/MCC status and inpatient edits

As a secondary diagnosis, I46.8 is an MCC under MS-DRG v44, unless the principal diagnosis is one of the 25 codes in its exclusion list and only when the patient is discharged alive. Check I46.8 against a principal diagnosis.

  • Present on admission: a POA indicator is required on inpatient claims.
  • Medicare Code Editor: unacceptable principal diagnosis.

CMS-HCC V28 risk adjustment

In the PY2027 mapping, I46.8 maps to HCC 213 (Cardio-Respiratory Failure and Shock). The HCC lookup shows the RAF weight and the hierarchy.

LCD billing and coding articles that list I46.8

26 current Medicare billing and coding articles list I46.8 among the diagnoses that support medical necessity for the services they cover.

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Frequently asked questions

What does ICD-10-CM I46.8 mean?

I46.8 means cardiac arrest due to other underlying condition. It is one of 3 billable codes under I46, cardiac arrest.

Which MS-DRG does I46.8 group to?

As the principal diagnosis, I46.8 groups to MS-DRG 296 Cardiac Arrest, Unexplained with MCC, MS-DRG 297 Cardiac Arrest, Unexplained with CC, MS-DRG 298 Cardiac Arrest, Unexplained without CC/MCC (MDC 05 MDC 05: Diseases and Disorders of the Circulatory System); or MS-DRG 791 Prematurity with Major Problems, MS-DRG 793 Full Term Neonate with Major Problems (MDC 15 MDC 15: Newborns and Other Neonates with Conditions Originating in Perinatal Period) under MS-DRG v44, before procedures and secondary diagnoses are applied.

Does I46.8 map to an HCC?

Yes: HCC 213, Cardio-Respiratory Failure and Shock, in the PY2027 CMS-HCC V28 mapping.

Is I46.8 a CC or MCC?

I46.8 is an MCC under MS-DRG v44; 25 principal diagnoses exclude it.

Sources

Every figure on this page is taken from the CMS publications below, as released by the Centers for Medicare & Medicaid Services. Projection built 2026-10-10. Verify against the primary file before billing or contracting decisions. The reference methodology explains how each figure is computed from these files.

Disclaimer

The descriptor and notes are reproduced from the FY2027 ICD-10-CM files; MS-DRG, CC/MCC and HCC facts come from the CMS FY2027 and PY2027 tables. Code from the medical record and the ICD-10-CM Official Guidelines. Not legal, clinical or billing advice.

Found a figure that does not match the CMS file? Report a data correction with the CMS file and the value you expected; the request reaches the editorial team through the contact form.