Alphabetic Index FY2027

I21

Acute myocardial infarction

FY2027Chapter 9: Diseases of the circulatory system/I20–I25 Ischemic heart diseases

Non-billable headerNot valid on its own. Use one of the more specific codes under it.

I21 is a non-billable ICD-10-CM code category for acute myocardial infarction. Report a more specific code from it instead. It is part of the FY2027 code set, effective October 1, 2026. The more specific codes under it are 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 and 4 more. Its coding notes include a Use additional code instruction, a Code also instruction and 13 Excludes2 entries.

Guidelines tip

From the FY2027 Official Guidelines. ICD10Ref adds no rules of its own.

I21 may continue to be reported while the MI is four weeks old or less. After that, continuing care is coded as aftercare, and a healed MI may be coded I25.2.

Guidelines I.C.9.e.1Acute myocardial infarction: the four-week time frameRead the official text

Use additional code

Add the listed code as a secondary code, if known.

This 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)

Code also

Two codes may be needed to describe the condition. This note gives no sequencing order.

Also from chapter/block level (1 note)
Inherited from I20–I25 Ischemic heart diseases
  • the presence of hypertension (I10-I1A)

Excludes2

Not included here. Both codes may be reported if the patient has both conditions.

This code
  • old myocardial infarction (I25.2)
  • postmyocardial infarction syndrome (I24.1)
  • subsequent type 1 myocardial infarction (I22.-)
Also from chapter/block level (10 notes)
Inherited from Chapter 9 Diseases of the circulatory system
  • certain conditions originating in the perinatal period (P04-P96)
  • certain infectious and parasitic diseases (A00-B99)
  • complications of pregnancy, childbirth and the puerperium (O00-O9A)
  • congenital malformations, deformations, and chromosomal abnormalities (Q00-Q99)
  • endocrine, nutritional and metabolic diseases (E00-E88)
  • injury, poisoning and certain other consequences of external causes (S00-T88)
  • neoplasms (C00-D49)
  • symptoms, signs and abnormal clinical and laboratory findings, not elsewhere classified (R00-R94)
  • systemic connective tissue disorders (M30-M36)
  • transient cerebral ischemic attacks and related syndromes (G45.-)

Includes

Further defines or gives examples of the content of the category.

This code
  • 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

More specific codes under I21 8