U.S. ICD-10-CM · FY 2027

I21 ICD-10-CM Code: Acute myocardial infarction

A clear reference for the official code description, hierarchy, and related coding information from the FY 2027 U.S. release.

Code definition

Official description

I21

Acute myocardial infarction

ICD-10-CM diagnosis code · United States clinical modification

Classification

Where I21 sits

  1. 1

    Chapter 9

    Diseases of the circulatory system (I00-I99)

  2. 2

    Section

    Ischemic heart diseases (I20-I25)

  3. 3

    Category I21

    Acute myocardial infarction

  4. 4

    Code I21

    Acute myocardial infarction

More specific choices

Codes under I21

I21 is a non-billable category. Choose the child code that best matches the documented diagnosis.

I21.0

ST elevation (STEMI) myocardial infarction of anterior wall

I21.1

ST elevation (STEMI) myocardial infarction of inferior wall

I21.2

ST elevation (STEMI) myocardial infarction of other sites

I21.3

ST elevation (STEMI) myocardial infarction of unspecified site

I21.4

Non-ST elevation (NSTEMI) myocardial infarction

I21.9

Acute myocardial infarction, unspecified

I21.A

Other type of myocardial infarction

I21.B

Myocardial infarction with coronary microvascular dysfunction

Documentation details

Notes for this code

Inclusion terms

No inclusion terms are listed for I21.

Code first

No “code first” instruction is listed for I21.

Use additional code

  • 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)

Excludes1

Conditions that should not be reported together with this code.

No Excludes1 note is listed for I21.

Excludes2

Conditions not included here that may be reported separately when present.

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

Transparency

Source and release

Data release

U.S. ICD-10-CM · FY 2027

Effective date

Oct 1, 2026

Publisher

Vero Scribe Inc.

This reference is generated from Vero’s ICD-10-CM description, hierarchy, and code-note dataset. The visible content and structured data share that source.

Review the CDC/NCHS ICD-10-CM source

Code-specific guidance

Frequently asked questions

What does ICD-10-CM code I21 mean?

I21 is the FY 2027 U.S. ICD-10-CM code for “Acute myocardial infarction.”

Is I21 a billable or specific ICD-10-CM code?

No. I21 has more specific child codes in the FY 2027 reference data. Select the code that matches the documentation and confirm the active code set and payer requirements.

Where is I21 located in ICD-10-CM?

I21 is listed in Chapter 9, Diseases of the circulatory system (I00-I99), within Ischemic heart diseases (I20-I25) (I20–I25), under category I21, Acute myocardial infarction.

What coding notes are listed for I21?

No inclusion terms are listed for I21 in this reference record. No code-first instruction is listed. Additional-code instructions: 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). No Excludes1 note is listed. Excludes2 notes: old myocardial infarction (I25.2); postmyocardial infarction syndrome (I24.1); subsequent type 1 myocardial infarction (I22.-).

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