ICD-10 Code I21.01 – ST elevation (STEMI) myocardial infarction involving left main coronary artery (2026): Diagnosis, Symptoms & Billing Guide
2026 ICD-10-CM Diagnosis Code I21.01 – ST elevation (STEMI) myocardial infarction involving left main coronary artery
What it is
This code identifies an acute ST-elevation myocardial infarction caused by blockage of the left main coronary artery. It reflects a major heart attack affecting blood flow to a large portion of the left heart.
Clinical signs
Typical findings include acute chest pain or pressure, ischemic ECG changes with ST elevation, and evidence of myocardial injury. Clinical features vary; refer to documentation.
When to use this code
Use I21.01 when the provider documents STEMI involving the left main coronary artery. Apply it when the infarct location is clearly specified in the final diagnosis, discharge summary, or cardiology note.
If the record only states STEMI without a coronary artery location, check documentation before assigning this code. You should not infer left main involvement from nonspecific ischemic findings.
Do not use for
Do not use this code for NSTEMI, old myocardial infarction, or unspecified acute MI. Check documentation if the coronary artery involved is not clearly identified.
Coding tip
Code the artery named by the provider; if left main involvement is absent from the record, do not assume I21.01.