DxCodebookFY2027 · Oct 1, 2026 – Sep 30, 2027

Category · FY2027

I21 Acute myocardial infarction

  • Header · not billable

I21 is not billable. The category heads 13 billable codes in FY2027, grouped under 8 subdivisions.

Index → code

  • STEMI → I21.3
  • Infarct, infarctionnontransmural → I21.4
  • Necrosis, necrotic (ischemic)subendocardial (acute) → I21.4

Where it sits

  1. Chapter 9 Diseases of the circulatory system (I00-I99)
  2. I20-I25 Ischemic heart diseases (I20-I25)
  3. I21 Acute myocardial infarction
Billable codes
13
Subdivisions
8
CC / MCC codes
0 / 13
HCC V28 codes
13
New FY2027
0
Index entries
54

Codes in I21

  1. I21.0
    ST elevation (STEMI) myocardial infarction of anterior wall
    Header
    Inclusion terms 1

    Inclusion terms

    • Type 1 ST elevation myocardial infarction of anterior wall
  2. I21.01
    ST elevation (STEMI) myocardial infarction involving left main coronary artery
    BillableMCC228
  3. I21.02
    ST elevation (STEMI) myocardial infarction involving left anterior descending coronary artery
    BillableMCC228
    Inclusion terms 1

    Inclusion terms

    • ST elevation (STEMI) myocardial infarction involving diagonal coronary artery
  4. I21.09
    ST elevation (STEMI) myocardial infarction involving other coronary artery of anterior wall
    BillableMCC228
    Inclusion terms 5

    Inclusion terms

    • Acute transmural myocardial infarction of anterior wall
    • Anteroapical transmural (Q wave) infarction (acute)
    • Anterolateral transmural (Q wave) infarction (acute)
    • Anteroseptal transmural (Q wave) infarction (acute)
    • Transmural (Q wave) infarction (acute) (of) anterior (wall) NOS
  5. I21.1
    ST elevation (STEMI) myocardial infarction of inferior wall
    Header
    Inclusion terms 1

    Inclusion terms

    • Type 1 ST elevation myocardial infarction of inferior wall
  6. I21.11
    ST elevation (STEMI) myocardial infarction involving right coronary artery
    BillableMCC228
    Inclusion terms 1

    Inclusion terms

    • Inferoposterior transmural (Q wave) infarction (acute)
  7. I21.19
    ST elevation (STEMI) myocardial infarction involving other coronary artery of inferior wall
    BillableMCC228
    Inclusion terms 4, Excludes2 1

    Inclusion terms

    • Acute transmural myocardial infarction of inferior wall
    • Inferolateral transmural (Q wave) infarction (acute)
    • Transmural (Q wave) infarction (acute) (of) diaphragmatic wall
    • Transmural (Q wave) infarction (acute) (of) inferior (wall) NOS

    Excludes2

    • ST elevation (STEMI) myocardial infarction involving left circumflex coronary artery (I21.21) I21.21
  8. I21.2
    ST elevation (STEMI) myocardial infarction of other sites
    Header
    Inclusion terms 1

    Inclusion terms

    • Type 1 ST elevation myocardial infarction of other sites
  9. I21.21
    ST elevation (STEMI) myocardial infarction involving left circumflex coronary artery
    BillableMCC228
    Inclusion terms 1

    Inclusion terms

    • ST elevation (STEMI) myocardial infarction involving oblique marginal coronary artery
  10. I21.29
    ST elevation (STEMI) myocardial infarction involving other sites
    BillableMCC228
    Inclusion terms 10

    Inclusion terms

    • Acute transmural myocardial infarction of other sites
    • Apical-lateral transmural (Q wave) infarction (acute)
    • Basal-lateral transmural (Q wave) infarction (acute)
    • High lateral transmural (Q wave) infarction (acute)
    • Lateral (wall) NOS transmural (Q wave) infarction (acute)
    • Posterior (true) transmural (Q wave) infarction (acute)
    • Posterobasal transmural (Q wave) infarction (acute)
    • Posterolateral transmural (Q wave) infarction (acute)
    • Posteroseptal transmural (Q wave) infarction (acute)
    • Septal transmural (Q wave) infarction (acute) NOS
  11. I21.3
    ST elevation (STEMI) myocardial infarction of unspecified site
    BillableMCC228
    Inclusion terms 3

    Inclusion terms

    • Acute transmural myocardial infarction of unspecified site
    • Transmural (Q wave) myocardial infarction NOS
    • Type 1 ST elevation myocardial infarction of unspecified site
  12. I21.4
    Non-ST elevation (NSTEMI) myocardial infarction
    BillableMCC228
    Inclusion terms 4

    Inclusion terms

    • Acute subendocardial myocardial infarction
    • Non-Q wave myocardial infarction NOS
    • Nontransmural myocardial infarction NOS
    • Type 1 non-ST elevation myocardial infarction
  13. I21.9
    Acute myocardial infarction, unspecified
    BillableMCC228
    Inclusion terms 1

    Inclusion terms

    • Myocardial infarction (acute) NOS
  14. I21.A
    Other type of myocardial infarction
    Header
  15. I21.A1
    Myocardial infarction type 2
    BillableMCC228
    Inclusion terms 2, Code first 5

    Inclusion terms

    • Myocardial infarction due to demand ischemia
    • Myocardial infarction secondary to ischemic imbalance

    Code first

    • , if applicable, the underlying cause, such as:
    • anemia (D50.0-D64.9) D50.0 D64.9
    • chronic obstructive pulmonary disease (J44.-) J44
    • paroxysmal tachycardia (I47.0-I47.9) I47.0 I47.9
    • shock (R57.0-R57.9) R57.0 R57.9
  16. I21.A9
    Other myocardial infarction type
    BillableMCC228
    Inclusion terms 6, Code first 1, Code also 7

    Inclusion terms

    • Myocardial infarction associated with revascularization procedure
    • Myocardial infarction type 3
    • Myocardial infarction type 4a
    • Myocardial infarction type 4b
    • Myocardial infarction type 4c
    • Myocardial infarction type 5

    Code first

    • , if applicable, postprocedural myocardial infarction following cardiac surgery (I97.190), or postprocedural myocardial infarction during cardiac surgery (I97.790) I97.190 I97.790

    Code also

    • complication, if known and applicable, such as:
    • (acute) stent occlusion (T82.897-) T82.897
    • (acute) stent stenosis (T82.855-) T82.855
    • (acute) stent thrombosis (T82.867-) T82.867
    • cardiac arrest due to underlying cardiac condition (I46.2) I46.2
    • complication of percutaneous coronary intervention (PCI) (I97.89) I97.89
    • occlusion of coronary artery bypass graft (T82.218-) T82.218
  17. I21.B
    Myocardial infarction with coronary microvascular dysfunction
    BillableMCC228
    Inclusion terms 2

    Inclusion terms

    • Myocardial infarction with coronary microvascular disease
    • Myocardial infarction with nonobstructive coronary arteries [MINOCA] with microvascular disease

CC/MCC: as a secondary diagnosis, unless the principal diagnosis is on the code’s PDX exclusion list (MS-DRG v44 Appendix C; list on the code card).

Sources of each column.

Instructions

At I21

Includes

  • 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

Excludes2

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

Use additional code

  • code, if applicable, to identify:
  • exposure to environmental tobacco smoke (Z77.22) Z77.22
  • history of tobacco dependence (Z87.891) Z87.891
  • occupational exposure to environmental tobacco smoke (Z57.31) 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) Z92.82
  • tobacco dependence (F17.-) F17
  • tobacco use (Z72.0) Z72.0

Notes that also apply

Block I20-I25 instructions (Code also 1): printed on the block page.

Chapter 9 instructions (Excludes2 10): printed on the chapter 9 page.

Index entries

  • STEMI → I21.3
  • Infarct, infarctionnontransmural → I21.4
  • Infarct, infarctionsubendocardial (acute) (nontransmural) → I21.4
  • Necrosis, necrotic (ischemic)subendocardial (acute) → I21.4
  • Infarct, infarctionmyocardium, myocardial (acute) (with stated duration of 4 weeks or less) → I21.9
  • Infarct, infarctionmyocardium, myocardial (acute) (with stated duration of 4 weeks or less)Q wave (see also, Infarct, myocardium, ST elevation, by site) → I21.3
  • Infarct, infarctionmyocardium, myocardial (acute) (with stated duration of 4 weeks or less)ST elevation (STEMI) → I21.3
  • Infarct, infarctionmyocardium, myocardial (acute) (with stated duration of 4 weeks or less)transmural (see also, Infarct, myocardium, ST elevation, by site) → I21.3
  • Infarct, infarctionmyocardium, myocardial (acute) (with stated duration of 4 weeks or less)non-Q wave → I21.4
  • Infarct, infarctionmyocardium, myocardial (acute) (with stated duration of 4 weeks or less)non-ST elevation (NSTEMI) → I21.4
  • Infarct, infarctionmyocardium, myocardial (acute) (with stated duration of 4 weeks or less)nontransmural → I21.4
  • Infarct, infarctionmyocardium, myocardial (acute) (with stated duration of 4 weeks or less)type 1 → I21.9
  • Infarct, infarctionmyocardium, myocardial (acute) (with stated duration of 4 weeks or less)type 2 → I21.A1
  • Ischemia, ischemicdemand (coronary)with myocardial infarction → I21.A1
  • Ischemia, ischemicdemand (coronary)resulting in myocardial infarction → I21.A1
  • Infarct, infarctionmyocardium, myocardial (acute) (with stated duration of 4 weeks or less)associated with revascularization procedure → I21.A9
  • Infarct, infarctionmyocardium, myocardial (acute) (with stated duration of 4 weeks or less)type 3 → I21.A9
  • Infarct, infarctionmyocardium, myocardial (acute) (with stated duration of 4 weeks or less)type 4(a) (b) (c) → I21.A9
  • Infarct, infarctionmyocardium, myocardial (acute) (with stated duration of 4 weeks or less)type 5 → I21.A9
  • Infarct, infarctionmyocardium, myocardial (acute) (with stated duration of 4 weeks or less)ST elevation (STEMI)anterior (anteroapical) (anterolateral) (anteroseptal) (Q wave) (wall) → I21.09
  • Infarct, infarctionmyocardium, myocardial (acute) (with stated duration of 4 weeks or less)transmural (see also, Infarct, myocardium, ST elevation, by site)anterior (anteroapical) (anterolateral) (anteroseptal) (Q wave) (wall) NEC → I21.09
  • Infarct, infarctionmyocardium, myocardial (acute) (with stated duration of 4 weeks or less)ST elevation (STEMI)inferoposterior transmural (Q wave) → I21.11
  • Infarct, infarctionmyocardium, myocardial (acute) (with stated duration of 4 weeks or less)transmural (see also, Infarct, myocardium, ST elevation, by site)inferoposterior (Q wave) → I21.11
  • Infarct, infarctionmyocardium, myocardial (acute) (with stated duration of 4 weeks or less)ST elevation (STEMI)inferior (diaphragmatic) (inferolateral) (inferoposterior) (wall) NEC → I21.19
  • Infarct, infarctionmyocardium, myocardial (acute) (with stated duration of 4 weeks or less)transmural (see also, Infarct, myocardium, ST elevation, by site)inferior (diaphragmatic) (inferolateral) (inferoposterior) (Q wave) (wall) NEC → I21.19
  • Infarct, infarctionmyocardium, myocardial (acute) (with stated duration of 4 weeks or less)ST elevation (STEMI)lateral (apical-lateral) (basal-lateral) (high) → I21.29
  • Infarct, infarctionmyocardium, myocardial (acute) (with stated duration of 4 weeks or less)ST elevation (STEMI)posterior (posterobasal) (posterolateral) (posteroseptal) (true) → I21.29
  • Infarct, infarctionmyocardium, myocardial (acute) (with stated duration of 4 weeks or less)ST elevation (STEMI)septal → I21.29
  • Infarct, infarctionmyocardium, myocardial (acute) (with stated duration of 4 weeks or less)ST elevation (STEMI)specified NEC → I21.29
  • Infarct, infarctionmyocardium, myocardial (acute) (with stated duration of 4 weeks or less)transmural (see also, Infarct, myocardium, ST elevation, by site)lateral (apical-lateral) (basal-lateral) (high) NEC → I21.29
  • Infarct, infarctionmyocardium, myocardial (acute) (with stated duration of 4 weeks or less)transmural (see also, Infarct, myocardium, ST elevation, by site)posterior (posterobasal) (posterolateral) (posteroseptal) (true) NEC → I21.29
  • Infarct, infarctionmyocardium, myocardial (acute) (with stated duration of 4 weeks or less)transmural (see also, Infarct, myocardium, ST elevation, by site)septal NEC → I21.29
  • Infarct, infarctionmyocardium, myocardial (acute) (with stated duration of 4 weeks or less)transmural (see also, Infarct, myocardium, ST elevation, by site)specified NEC → I21.29
  • Infarct, infarctionmyocardium, myocardial (acute) (with stated duration of 4 weeks or less)due todemand ischemia → I21.A1
  • Infarct, infarctionmyocardium, myocardial (acute) (with stated duration of 4 weeks or less)due toischemic imbalance → I21.A1
  • Infarct, infarctionmyocardium, myocardial (acute) (with stated duration of 4 weeks or less)secondary todemand ischemia → I21.A1
  • Infarct, infarctionmyocardium, myocardial (acute) (with stated duration of 4 weeks or less)secondary toischemic imbalance → I21.A1
  • Infarct, infarctionmyocardium, myocardial (acute) (with stated duration of 4 weeks or less)subsequent (recurrent) (reinfarction)type 2 → I21.A1
  • Infarct, infarctionmyocardium, myocardial (acute) (with stated duration of 4 weeks or less)subsequent (recurrent) (reinfarction)type 3 → I21.A9
  • Infarct, infarctionmyocardium, myocardial (acute) (with stated duration of 4 weeks or less)subsequent (recurrent) (reinfarction)type 4 → I21.A9

14 more, longer entries are not listed; the search box finds them by word.

NCHS Alphabetic Index. Index first, then the Tabular List.

Hierarchy