2026 ICD-10-CM Diagnosis Code I21.19ST elevation (STEMI) myocardial infarction involving other coronary artery of inferior wall
ICD-10-CM Codes›I00–I99›I20-I25›I21
- Billable — Valid for Submission
- Chronic Condition
I21.19 is a billable ICD-10-CM diagnosis code for ST elevation (STEMI) myocardial infarction involving other coronary artery of inferior wall. It is valid on HIPAA claims for fiscal year 2026 (October 1, 2025 through September 30, 2026) and groups to MS-DRG 280 through 285. In AHRQ's Clinical Classifications Software (CCSR), this diagnosis falls under Acute myocardial infarction.
This medical diagnosis code is frequently used in Cardiology medical specialties to designate conditions such selected atherosclerosis, ischemia, and infarction.
Code Identity
Code Classification
Approximate SynonymsGuidance
Alternate terms and clinical phrases that map to this code.
- Acute myocardial infarction of inferior wall
- Acute myocardial infarction of inferior wall involving right ventricle
- Acute myocardial infarction of inferolateral wall
- Acute myocardial infarction of inferoposterior wall
- Acute Q wave infarction - inferior
- Acute Q wave infarction - inferolateral
- Acute Q wave infarction - lateral
- Acute Q wave myocardial infarction
- Acute ST segment elevation myocardial infarction of inferior wall
- Acute ST segment elevation myocardial infarction of inferior wall involving right ventricle
- Acute ST segment elevation myocardial infarction of inferolateral wall
- Acute ST segment elevation myocardial infarction of inferoposterior wall
- Acute ST segment elevation myocardial infarction of lateral wall
- Postoperative myocardial infarction
- Postoperative transmural myocardial infarction of inferior wall
Tabular List NotesGuidance
Coding notes and annotation back-references applicable to this code.
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
Type 2 Excludes
- ST elevation STEMI myocardial infarction involving left circumflex coronary artery I21.21
These terms are the conditions for which that code is to be used. The terms may be synonyms of the code title, or, in the case of "other specified" codes, the terms are a list of the various conditions assigned to that code. The inclusion terms are not necessarily exhaustive. Additional terms found only in the Alphabetic Index may also be assigned to a code.
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.
Index to Diseases and InjuriesGuidance
Alphabetical index entries that point to this code.
External Cause of Injuries IndexGuidance
References for this code in the External Cause of Injuries Index.
- 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)
- ST elevation (STEMI)
- involving
- coronary artery of inferior 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
Clinical ClassificationClinical
AHRQ’s CCSR groups this code into broader clinical categories.
Patient EducationClinical
Heart Attack
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Read the full article at MedlinePlus
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Convert I21.19 to ICD-9-CMHistory
Code HistoryHistory
Questions About I21.19Overview
Is I21.19 (ST elevation (STEMI) myocardial infarction of inferior wall) a billable code?
Yes. This is a billable ICD-10-CM code, specific enough to report ST elevation (STEMI) myocardial infarction involving other coronary artery of inferior wall on HIPAA-covered claims from October 1, 2025 through September 30, 2026.
What MS-DRG does I21.19 group to?
When ST elevation (STEMI) myocardial infarction involving other coronary artery of inferior wall is the principal diagnosis on an inpatient stay, it groups to MS-DRG 280, 281, 282, 283, 284, 285, with relative weights from 0.5989 to 1.9808 depending on complications. Higher weights mean higher Medicare reimbursement.
What is the ICD-9 equivalent of I21.19?
Under the General Equivalence Mappings, ST elevation (STEMI) myocardial infarction involving other coronary artery of inferior wall converts to ICD-9-CM 410.21 (AMI inferolateral, init) and 410.41 (AMI inferior wall, init). The mapping is approximate, so confirm the match fits the documentation.
Footnotes
[1] Chronic - a chronic condition code indicates a condition lasting 12 months or longer and its effect on the patient based on one or both of the following criteria:
- The condition results in the need for ongoing intervention with medical products,treatment, services, and special equipment
- The condition places limitations on self-care, independent living, and social interactions.
