I21.21 – ST elevation (STEMI) myocardial infarction involving left circumflex coronary artery
ICD-10-CM 2027 diagnosis code · Ischemic heart diseases
ICD-10-CM code
I21.21
- Code
I21.21(claims format:I2121)- Description
- ST elevation (STEMI) myocardial infarction involving left circumflex coronary artery
- Short description
- STEMI involving left circumflex coronary artery
- Billable
- Yes – valid for HIPAA-covered transactions
- Valid for
- Dates of service October 1, 2026 – September 30, 2027 (FY2027)
- Chapter
- 9. Diseases of the circulatory system (I00-I99)
- Block
- I20-I25 Ischemic heart diseases
- Parent codes
- I21 › I21.2
Notes for I21.21
Applicable to:
- ST elevation (STEMI) myocardial infarction involving oblique marginal coronary artery
Notes inherited from parent codes
Instructional notes at a category or block level apply to every code below it.
I21 – Acute myocardial infarction
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 (not included here):
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)
I21.2 – ST elevation (STEMI) myocardial infarction of other sites
Applicable to:
- Type 1 ST elevation myocardial infarction of other sites
Block I20-I25
Index terms for I21.21
Entries in the ICD-10-CM alphabetic index that lead to this code:
Related codes in I21.2
Frequently asked questions
What is ICD-10 code I21.21?
I21.21 is the ICD-10-CM code for sT elevation (STEMI) myocardial infarction involving left circumflex coronary artery, in the block I20-I25 (Ischemic heart diseases).
Is I21.21 a billable code?
Yes. I21.21 is a billable/specific code that can be used to indicate a diagnosis for reimbursement purposes.
What category does I21.21 belong to?
It belongs to category I21 – Acute myocardial infarction.
Source: CDC/NCHS ICD-10-CM FY2027 code files, tabular list and index. Reference only – code assignment must follow the official ICD-10-CM guidelines and documentation in the medical record.