I21.19 ST elevation (STEMI) myocardial infarction involving other coronary artery of inferior wall
The ICD-10-CM code for ST elevation (STEMI) myocardial infarction involving other coronary artery of inferior wall is I21.19 (FY2026). It is a billable, claim-ready diagnosis code.
Classification
- 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 I21.19:
- Infarct, infarction › myocardium, myocardial (acute) (with stated duration of 4 weeks or less) › ST elevation (STEMI) › inferior (diaphragmatic) (inferolateral) (inferoposterior) (wall) NEC
- Infarct, infarction › myocardium, 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
- Infarct, infarction › myocardium, myocardial (acute) (with stated duration of 4 weeks or less) › ST elevation (STEMI) › involving › coronary artery of inferior wall NEC
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
U.S. Hospital Utilization
- An estimated 64,335 U.S. inpatient stays in 2023 included I21.19 among the documented diagnoses.
- 52,700 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
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.
Provider must link conditions not specifically indexed as relatedFor hypertension and conditions not specifically linked by relational terms such as “with,” “associated with” or “due to” in the classification, provider documentation must link the conditions in order to code them as related.
Source: CMS — ICD-10-CM Official Guidelines for Coding and Reporting, FY2026