I21.02 ST elevation (STEMI) myocardial infarction involving left anterior descending coronary artery

The ICD-10-CM code for ST elevation (STEMI) myocardial infarction involving left anterior descending coronary artery is I21.02 (FY2026). It is a billable, claim-ready diagnosis code.

Classification

Chapter

9: Diseases of the circulatory system (I00-I99)

Section

I20-I25: Ischemic heart diseases (I20-I25)

Category I21

18 codes (13 billable)

FY2026 Status

Stable since FY2024

Also Known As

ICD-10-CM Alphabetic Index entries that lead to I21.02:

• Infarct, infarction › myocardium, myocardial (acute) (with stated duration of 4 weeks or less) › ST elevation (STEMI) › involving › diagonal coronary artery
• Infarct, infarction › myocardium, myocardial (acute) (with stated duration of 4 weeks or less) › ST elevation (STEMI) › involving › left anterior descending coronary artery

Inclusion Terms

• ST elevation (STEMI) myocardial infarction involving diagonal coronary artery

U.S. Hospital Utilization

• An estimated 28,065 U.S. inpatient stays in 2023 included I21.02 among the documented diagnoses.
• 23,855 stays listed it as the principal diagnosis.

Source: National Inpatient Sample (NIS), Healthcare Cost and Utilization Project (HCUP), Agency for Healthcare Research and Quality, 2016–2023. National survey-weighted estimates.

Official Coding Guidelines

Type 1 STEMI/NSTEMI code selection and conversion rules

e. Acute myocardial infarction (AMI) 1) Type 1 ST elevation myocardial infarction (STEMI) and non- ST elevation myocardial infarction (NSTEMI) The ICD-10-CM codes for type 1 acute myocardial infarction (AMI) identify the site, such as anterolateral wall or true posterior wall. Subcategories I21.0-I21.2 and code I21.3 are used for type 1 ST elevation myocardial infarction (STEMI). Code I21.4, Non-ST elevation (NSTEMI) myocardial infarction, is used for type 1 non-ST elevation myocardial infarction (NSTEMI) and nontransmural MIs. If a type 1 NSTEMI evolves to STEMI, assign the STEMI code. If a type 1 STEMI converts to NSTEMI due to thrombolytic therapy, it is still coded as STEMI.

Presumed relationship due to Index term “with”

The classification presumes a causal relationship between hypertension and heart involvement and between hypertension and kidney involvement, as the two conditions are linked by the term “with” in the Alphabetic Index. These conditions should be coded as related even in the absence of provider documentation explicitly linking them, unless the documentation clearly states the conditions are unrelated.

Source: CMS — ICD-10-CM Official Guidelines for Coding and Reporting, FY2026

References

• CMS — ICD-10-CM Official Code Set and Guidelines, FY2026
• CDC/NCHS — ICD-10-CM Files and Browser Tool
• AHRQ — HCUP National Inpatient Sample, Frequencies by Diagnosis Code (2016–2023)