ICD-10 Code I21.1 – ST elevation (STEMI) myocardial infarction of inferior wall (2026): Diagnosis, Symptoms & Billing Guide
2026 ICD-10-CM Diagnosis Code I21.1 – ST elevation (STEMI) myocardial infarction of inferior wall
What it is
I21.1 identifies an acute ST-elevation myocardial infarction affecting the inferior wall of the heart. Use it when the record clearly states STEMI with inferior wall involvement.
Clinical signs
Typical documentation includes acute chest pain or ischemic symptoms with ECG evidence of ST elevation and a clinician diagnosis of inferior-wall STEMI. Clinical features vary; refer to documentation.
When to use this code
Use this code when the provider documents an acute STEMI limited to, or primarily involving, the inferior wall. It is appropriate for emergency, inpatient, or discharge records that explicitly name inferior-wall STEMI. Check documentation if the location is unclear or if the event is described only as MI without ST elevation.
Do not use for
Do not use it for NSTEMI, old or healed myocardial infarction, or nonspecific chest pain. Do not assume inferior-wall involvement unless the record states it.
Coding tip
Code the infarct location exactly as documented, and confirm whether the event is acute STEMI before assigning I21.1.