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HCC Buddy
HCC Buddy
Alphabetic Index and Tabular path
HCC Buddy public API, FY2026 Apr updateSource load source requiredSource year 2026Updated 2026-04-01

Index trail

Non-ST elevation (NSTEMI) myocardial infarction

See Tabular List: I21.4

I21, Acute myocardial infarction

I21.4, Non-ST elevation (NSTEMI) myocardial infarction

Selected code, source checked for the selected effective period

Commonly confused codes

official source

Not listed for this effective period.

Code details and official notes

I21.4

Non-ST elevation (NSTEMI) myocardial infarction

Open the shareable code page for I21.4→
billableHCC mapped

Includes

official source
  • Acute subendocardial myocardial infarction
  • Non-Q wave myocardial infarction NOS
  • Nontransmural myocardial infarction NOS
  • Type 1 non-ST elevation myocardial infarction
  • cardiac infarction
  • coronary (artery) embolism
  • coronary (artery) occlusion
  • coronary (artery) rupture
  • coronary (artery) thrombosis
  • infarction of heart, myocardium, or ventricle
  • myocardial infarction specified as acute or with a stated duration of 4 weeks (28 days) or less from onset

Excludes 1

official source

No Excludes 1 note is listed in this source payload.

Excludes 2

official source
  • old myocardial infarction (I25.2)
  • postmyocardial infarction syndrome (I24.1)
  • subsequent type 1 myocardial infarction (I22.-)

Code First

official source

Not listed for this effective period.

Use Additional

official source
  • code, if applicable, to identify:
  • exposure to environmental tobacco smoke (Z77.22)
  • history of tobacco dependence (Z87.891)
  • occupational exposure to environmental tobacco smoke (Z57.31)
  • status post administration of tPA (rtPA) in a different facility within the last 24 hours prior to admission to current facility (Z92.82)
  • tobacco dependence (F17.-)
  • tobacco use (Z72.0)

Code Also

official source

Not listed for this effective period.

7th character

official source

Not listed for this code in the selected Tabular payload.

Placeholder X

official source

Not listed for this code in the selected Tabular payload.

Laterality

official source

No laterality instruction is listed for this code in the selected Tabular payload.

Effective period

source required
  • FY2026 Apr update
  • Source year 2026
  • Updated 2026-04-01
  • HCC Buddy public API
HCC Buddy
HCC Buddy
Alphabetic Index and Tabular path
HCC Buddy public API, FY2026 Apr updateSource load source requiredSource year 2026Updated 2026-04-01

Index trail

Non-ST elevation (NSTEMI) myocardial infarction

See Tabular List: I21.4

I21, Acute myocardial infarction

I21.4, Non-ST elevation (NSTEMI) myocardial infarction

Selected code, source checked for the selected effective period

Commonly confused codes

official source

Not listed for this effective period.

Code details and official notes

I21.4

Non-ST elevation (NSTEMI) myocardial infarction

Open the shareable code page for I21.4→
billableHCC mapped

Includes

official source
  • Acute subendocardial myocardial infarction
  • Non-Q wave myocardial infarction NOS
  • Nontransmural myocardial infarction NOS
  • Type 1 non-ST elevation myocardial infarction
  • cardiac infarction
  • coronary (artery) embolism
  • coronary (artery) occlusion
  • coronary (artery) rupture
  • coronary (artery) thrombosis
  • infarction of heart, myocardium, or ventricle
  • myocardial infarction specified as acute or with a stated duration of 4 weeks (28 days) or less from onset

Excludes 1

official source

No Excludes 1 note is listed in this source payload.

Excludes 2

official source
  • old myocardial infarction (I25.2)
  • postmyocardial infarction syndrome (I24.1)
  • subsequent type 1 myocardial infarction (I22.-)

Code First

official source

Not listed for this effective period.

Use Additional

official source
  • code, if applicable, to identify:
  • exposure to environmental tobacco smoke (Z77.22)
  • history of tobacco dependence (Z87.891)
  • occupational exposure to environmental tobacco smoke (Z57.31)
  • status post administration of tPA (rtPA) in a different facility within the last 24 hours prior to admission to current facility (Z92.82)
  • tobacco dependence (F17.-)
  • tobacco use (Z72.0)

Code Also

official source

Not listed for this effective period.

7th character

official source

Not listed for this code in the selected Tabular payload.

Placeholder X

official source

Not listed for this code in the selected Tabular payload.

Laterality

official source

No laterality instruction is listed for this code in the selected Tabular payload.

Effective period

source required
  • FY2026 Apr update
  • Source year 2026
  • Updated 2026-04-01
  • HCC Buddy public API
HCC Buddy Insights

HCC Mapping

HCC 228 Acute Myocardial Infarction (V28)HCC 86 Acute Myocardial Infarction (V24)HCC 188 Coronary Artery Disease and Angina (RxHCC)HCC 86 Acute Myocardial Infarction (ESRD/PACE)HCC 131 HHS-HCC 131; HHS-HCC 2026 benefit year (HHS-HCC)

RAF Value

V28: RAF: 0.252V24: RAF: 0.195RxHCC: RAF: 0.052ESRD/PACE: RAF: 0.151HHS-HCC: RAF: Varies by metal level

Model Period

FY2026 Apr update

Source

source required

Audit Caution

Close codes need documentation support before selection. Do not assume relationships.
Reviewed by the HCC Buddy Coding Team

HCC Buddy workflow band

HCC mapping, RAF, MEAT, source trail, and audit caution stay in view.

MEAT supportaudit cautionsource required

V28

HCC 228

Acute Myocardial Infarction

RAF: 0.252

V24

HCC 86

Acute Myocardial Infarction

RAF: 0.195

RxHCC

RxHCC 188

Coronary Artery Disease and Angina

RAF: 0.052

ESRD/PACE

HCC 86

Acute Myocardial Infarction

RAF: 0.151

HHS-HCC

HCC 131

HHS-HCC 131; HHS-HCC 2026 benefit year

RAF: Varies by metal level

MEAT checklist

Reviewed by the HCC Buddy Coding Team

Monitor, Evaluate, Assess, or Treat must be supported in the provider note.

HCC Buddy guidance, not official ICD-10-CM text.

Audit caution

Reviewed by the HCC Buddy Coding Team

Close codes need documentation support before selection. Do not assume relationships.

HCC Buddy guidance, not official ICD-10-CM text.

Reviewer sign-off

Reviewed by the HCC Buddy Coding Team

MEAT, documentation support, audit cautions, and close-code guidance are reviewed and approved for this effective period.

HCC Buddy enrichment is separate from official source text.

Last updated: April 1, 2026 · Not a substitute for official coding guidelines. No PHI or patient data.
HCC Buddy Code Card
FY 2026 Apr update
I21.4Billable

Non-ST elevation (NSTEMI) myocardial infarction

CMS-HCC V28

HCC 228

RAF 0.252

CMS-HCC V24

HCC 86

RAF 0.195

RxHCC

RxHCC 188

RAF 0.052

Reviewed by the HCC Buddy Coding TeamFY2026 Apr update

Code

I21.4

V28 HCC

HCC 228

RAF

0.252

Compare tray

Add close codes to compare documentation differences.