2019 ICD-10-CM Diagnosis Code I21.3

ST elevation (STEMI) myocardial infarction of unspecified site

    2016 2017 2018 2019 Billable/Specific Code
  • I21.3 is a billable/specific ICD-10-CM code that can be used to indicate a diagnosis for reimbursement purposes.
  • Short description: ST elevation (STEMI) myocardial infarction of unsp site
  • The 2019 edition of ICD-10-CM I21.3 became effective on October 1, 2018.
  • This is the American ICD-10-CM version of I21.3 - other international versions of ICD-10 I21.3 may differ.
Applicable To
  • Acute transmural myocardial infarction of unspecified site
  • Transmural (Q wave) myocardial infarction NOS
  • Type 1 ST elevation myocardial infarction of unspecified site
The following code(s) above I21.3 contain annotation back-references
Annotation Back-References
In this context, annotation back-references refer to codes that contain:
  • Applicable To annotations, or
  • Code Also annotations, or
  • Code First annotations, or
  • Excludes1 annotations, or
  • Excludes2 annotations, or
  • Includes annotations, or
  • Note annotations, or
  • Use Additional annotations
that may be applicable to I21.3:
  • I00-I99
    2019 ICD-10-CM Range I00-I99

    Diseases of the circulatory system

    Type 2 Excludes
    • 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.-)
    Diseases of the circulatory system
  • I20-I25
    2019 ICD-10-CM Range I20-I25

    Ischemic heart diseases

    Use Additional
    • code to identify presence of hypertension (I10-I16)
    Ischemic heart diseases
  • I21
    ICD-10-CM Diagnosis Code I21

    Acute myocardial infarction

      2016 2017 2018 - Revised Code 2019 Non-Billable/Non-Specific Code
    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
    Type 2 Excludes
    • old myocardial infarction (I25.2)
    • postmyocardial infarction syndrome (I24.1)
    • subsequent type 1 myocardial infarction (I22.-)
    Use Additional
    • 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)
    Acute myocardial infarction
Approximate Synonyms
  • Acute heart attack
  • Acute myocardial infarction
  • Acute myocardial infarction due to occlusion of left coronary artery
  • Acute st segment elevation myocardial infarction
  • Atrial septal defect after acute heart attack
  • Atrial septal defect as current complication following acute myocardial infarction
  • Chordae tendineae rupture after acute heart attack
  • Heart attack, acute
  • Heart attack, less than 8 weeks ago
  • Hemopericardium after acute heart attack
  • Hemopericardium as current complication following acute myocardial infarction
  • History of myocardial infarction less than 4 weeks ago
  • Hx of mi, < 8 weeks
  • Mi acute st segment elevation
  • Mural thrombus of heart, following heart attack
  • Myocardial infarction (heart attack)
  • Myocardial infarction (heart attack), < 4weeks
  • Post-infarction mural thrombus
  • Rupture of chordae tendinae as current complication following acute myocardial infarction
  • Rupture of interventricular septum
  • Rupture of interventricular septum following acute myocardial infarction
  • Rupture of papillary muscle as current complication following acute myocardial infarction
  • Rupture papillary muscle complicating acute heart attack
  • Subsequent heart attack, anterior wall, within 4 weeks of previous heart attack
  • Subsequent heart attack, anterolateral wall, within 4 weeks of previous heart attack
  • Subsequent heart attack, inferior wall, within 4 weeks of previous heart attack
  • Subsequent heart attack, inferolateral wall, within 4 weeks of previous heart attack
  • Subsequent heart attack, inferoposterior wall, within 4 weeks of previous heart attack
  • Subsequent heart attack, posterior wall, within 4 weeks of previous heart attack
  • Subsequent heart attack, posterolateral wall, within 4 weeks of previous heart attack
  • Subsequent heart attack, within 4 weeks of previous heart attack
  • Subsequent non-st elevation myocardial infarction, within 4 weeks of previous myocardial infarction
  • Subsequent st elevation anterior wall myocardial infarction, within 4 weeks of previous myocardial infarction
  • Subsequent st elevation anterolateral wall myocardial infarction, within 4 weeks of previous myocardial infarction
  • Subsequent st elevation inferior wall myocardial infarction, within 4 weeks of previous myocardial infarction
  • Subsequent st elevation inferolateral wall myocardial infarction, within 4 weeks of previous myocardial infarction
  • Subsequent st elevation inferoposterior wall myocardial infarction, within 4 weeks of previous myocardial infarction
  • Subsequent st elevation myocardial infarction, within 4 weeks of previous myocardial infarction
  • Subsequent st elevation posterior wall myocardial infarction, within 4 weeks of previous myocardial infarction
  • Subsequent st elevation posterolateral wall myocardial infarction, within 4 weeks of previous myocardial infarction
Clinical Information
  • Necrosis of the myocardium, as a result of interruption of the blood supply to the area. It is characterized by a severe and rapid onset of symptoms that may include chest pain, often radiating to the left arm and left side of the neck, dyspnea, sweating, and palpitations.
ICD-10-CM I21.3 is grouped within Diagnostic Related Group(s) (MS-DRG v36.0):
  • 222 Cardiac defibrillator implant with cardiac catheterization with ami/hf/shock with mcc
  • 223 Cardiac defibrillator implant with cardiac catheterization with ami/hf/shock without mcc
  • 224 Cardiac defibrillator implant with cardiac catheterization without ami/hf/shock with mcc
  • 225 Cardiac defibrillator implant with cardiac catheterization without ami/hf/shock without mcc
  • 226 Cardiac defibrillator implant without cardiac catheterization with mcc
  • 227 Cardiac defibrillator implant without cardiac catheterization without mcc
  • 280 Acute myocardial infarction, discharged alive with mcc
  • 281 Acute myocardial infarction, discharged alive with cc
  • 282 Acute myocardial infarction, discharged alive without cc/mcc
  • 283 Acute myocardial infarction, expired with mcc
  • 284 Acute myocardial infarction, expired with cc
  • 285 Acute myocardial infarction, expired without cc/mcc

Convert I21.3 to ICD-9-CM

Code History
  • 2016 (effective 10/1/2015): New code (first year of non-draft ICD-10-CM)
  • 2017 (effective 10/1/2016): No change
  • 2018 (effective 10/1/2017): No change
  • 2019 (effective 10/1/2018): No change

Diagnosis Index entries containing back-references to I21.3:
  • Infarct, infarction
    • myocardium, myocardial (acute) (with stated duration of 4 weeks or less) I21.9
      ICD-10-CM Diagnosis Code I21.9

      Acute myocardial infarction, unspecified

        2018 - New Code 2019 Billable/Specific Code
      Applicable To
      • Myocardial infarction (acute) NOS
      • ST elevation (STEMI) I21.3
      • Q wave I21.3 (see also, Infarct, myocardium, by site)
  • STEMI I21.3 - see also - Infarct, myocardium, ST elevation

ICD-10-CM Codes Adjacent To I21.3
I21.0 ST elevation (STEMI) myocardial infarction of anterior wall
I21.01 ST elevation (STEMI) myocardial infarction involving left main coronary artery
I21.02 ST elevation (STEMI) myocardial infarction involving left anterior descending coronary artery
I21.09 ST elevation (STEMI) myocardial infarction involving other coronary artery of anterior wall
I21.1 ST elevation (STEMI) myocardial infarction of inferior wall
I21.11 ST elevation (STEMI) myocardial infarction involving right coronary artery
I21.19 ST elevation (STEMI) myocardial infarction involving other coronary artery of inferior wall
I21.2 ST elevation (STEMI) myocardial infarction of other sites
I21.21 ST elevation (STEMI) myocardial infarction involving left circumflex coronary artery
I21.29 ST elevation (STEMI) myocardial infarction involving 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.A1 Myocardial infarction type 2
I21.A9 Other myocardial infarction type
I22 Subsequent ST elevation (STEMI) and non-ST elevation (NSTEMI) myocardial infarction
I22.0 Subsequent ST elevation (STEMI) myocardial infarction of anterior wall
I22.1 Subsequent ST elevation (STEMI) myocardial infarction of inferior wall
I22.2 Subsequent non-ST elevation (NSTEMI) myocardial infarction
I22.8 Subsequent ST elevation (STEMI) myocardial infarction of other sites

Reimbursement claims with a date of service on or after October 1, 2015 require the use of ICD-10-CM codes.