ICD-10 Code I22.9 – Subsequent ST elevation (STEMI) myocardial infarction of unspecified site (2026): Diagnosis, Symptoms & Billing Guide
2026 ICD-10-CM Diagnosis Code I22.9 – Subsequent ST elevation (STEMI) myocardial infarction of unspecified site
What it is
I22.9 identifies a new ST-elevation myocardial infarction that occurs soon after a recent myocardial infarction, when the affected site is not specified in the record. Use it only for a subsequent acute event, not the original infarction.
Clinical signs
Clinical features typically include acute ischemic chest pain, ECG evidence of ST elevation, and evidence of an acute myocardial infarction. Clinical features vary; refer to documentation.
When to use this code
Use I22.9 when documentation states a subsequent STEMI after a recent MI and does not identify the infarct location. It may appear in inpatient records, transfer notes, or specialist documentation describing a new acute event. You should confirm that the episode is truly subsequent, not a history or old infarction.
Do not use for
Do not use this code for the initial STEMI, old myocardial infarction, or nonspecific chest pain. Check documentation if the record does not clearly show a new infarction after a recent MI.
Coding tip
Verify the timing and whether the provider documents a new acute MI, because “subsequent” changes the code selection.