Acute myocardial infarction (I21) ICD-10-CM
The I21 code range covers acute myocardial infarction with 18 ICD-10-CM diagnosis codes. 13 of them are billable and valid for claim submission in fiscal year 2026, and the category headers group them but cannot themselves be billed.
Includes
This note appears immediately under a three character code title to further define, or give examples of, the content of the category.
- 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
Use Additional Code
The “use additional code” indicates that a secondary code could be used to further specify the patient’s condition. This note is not mandatory and is only used if enough information is available to assign an 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
Type 2 Excludes
A type 2 excludes note represents "Not included here". An excludes2 note indicates that the condition excluded is not part of the condition represented by the code, but a patient may have both conditions at the same time. When an Excludes2 note appears under a code, it is acceptable to use both the code and the excluded code together, when appropriate.
Codes in the I21 Range 18 codes · 13 billable
- I21 Acute myocardial infarctionNon-billable
- I21.0 ST elevation (STEMI) myocardial infarction of anterior wallNon-billable
- 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 wallNon-billable
- 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 sitesNon-billable
- 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 infarctionNon-billable
- I21.A1 Myocardial infarction type 2
- I21.A9 Other myocardial infarction type
- I21.B Myocardial infarction with coronary microvascular dysfunction
Clinical Terms in This Code Range
Definitions from the National Library of Medicine for conditions coded in the I21 range.
Anterior Wall Myocardial Infarction
MYOCARDIAL INFARCTION in which the anterior wall of the heart is involved. Anterior wall myocardial infarction is often caused by occlusion of the left anterior descending coronary artery. It can be categorized as anteroseptal or anterolateral wall myocardial infarction.
Inferior Wall Myocardial Infarction
MYOCARDIAL INFARCTION in which the inferior wall of the heart is involved. It is often caused by occlusion of the right coronary artery.
Kounis Syndrome
A disorder of cardiac function secondary to hypersensitivity reactions. It is characterized by coexistence of acute coronary syndromes and cardiac MAST CELL and PLATELET ACTIVATION. It may be induced by exposure to drugs (e.g., antibiotics, anesthetics, contrast media), food, and environmental triggers (e.g., insect bites and stings, poison ivy).
MINOCA
Myocardial infarction in the absence of obstructive coronary artery disease. CORONARY CIRCULATION disruption is due to various other factors such as ATHEROSCLEROTIC PLAQUE and CORONARY VASOSPASM.
Myocardial Infarction
NECROSIS of the MYOCARDIUM caused by an obstruction of the blood supply to the heart (CORONARY CIRCULATION).
Non-ST Elevated Myocardial Infarction
A myocardial infarction that does not produce elevations in the ST segments of the ELECTROCARDIOGRAM. ST segment elevation of the ECG is often used in determining the treatment protocol (see also ST Elevation Myocardial Infarction).
About the I21 Code Range
The ICD-10 code I21 and its subdivisions categorize various types of acute myocardial infarction (AMI), commonly known as a heart attack. These codes are used to specify the location and nature of the heart attack, including whether it involves ST elevation or not, and which coronary artery is affected.
This section includes codes such as I21.0 for anterior wall STEMI and I21.4 for non-ST elevation myocardial infarction (NSTEMI). Coders use terms like acute ST segment elevation myocardial infarction and synonyms like "Acute ST segment elevation myocardial infarction due to left coronary artery occlusion" (I21.01) or "Acute non-Q wave infarction" (I21.4) to assign precise codes. The codes also cover infarctions of specific coronary arteries (e.g., I21.11 for right coronary artery) and include unspecified or other myocardial infarction types (I21.9, I21.A). Detailed coding helps accurately document the myocardial infarction's cause, location, and severity, supporting clinical care and reporting. Searching for "ICD-10 code for acute ST elevation myocardial infarction" or "ICD-10 code for NSTEMI" leads to relevant I21 codes used in medical records and billing.
Questions About This Page
How many billable codes are in the I21 range?
Of the 18 codes in this range, 13 are billable and valid for claim submission from October 1, 2025 through September 30, 2026. Category header codes group them but cannot be reported on claims.
What does the I21 range classify?
The range classifies acute myocardial infarction. Each code links to its own reference page with billing status, MS-DRG grouping, coding notes, and clinical information.
Related References
Source: CMS FY 2026 ICD-10-CM Tabular List and order file, effective October 1, 2025 through September 30, 2026.
