I21.3 — ST elevation (STEMI) myocardial infarction of unspecified site

I21.3

ICD-10 Chapter 9: Circulatory System — illustrative image — Chapter 9: Diseases of the circulatory system (I00–I99) — illustrative image

What this code means

An ST-elevation myocardial infarction (STEMI) is a heart attack in which a coronary artery is completely blocked.

Also called: stemi, st elevation myocardial infarction, heart attack.

When this code is used

Used for STEMI of unspecified site.

Where it sits in ICD-10-CM

Code I21.3 belongs to Chapter 9: Diseases of the circulatory system, which covers codes I00–I99 in the FY2027 ICD-10-CM tabular list. The official description above is copied verbatim from the CDC/NCHS FY2027 code file.

Learn more about this condition

Condition guide: Heart Attack

Related symptoms

Chest pain

Related anatomy

Heart

Watch: related videos

▶ WatchAcute myocardial infarction heart attack ▶ WatchHeart attack and stroke ▶ WatchHeart attack animation

Frequently asked questions

What is ICD-10-CM code I21.3?

I21.3 is the ICD-10-CM diagnosis code for “ST elevation (STEMI) myocardial infarction of unspecified site”. An ST-elevation myocardial infarction (STEMI) is a heart attack in which a coronary artery is completely blocked.

When is code I21.3 used?

Used for STEMI of unspecified site. It belongs to Chapter 9 of ICD-10-CM (Diseases of the circulatory system).

This guide explains ICD-10-CM codes in plain language for patients, students and other readers. It is educational information only — not coding, billing or medical advice. The code recorded for any real encounter is assigned from the full clinical documentation by the treating team and qualified coders, and only they can decide which code fits a specific case.