I22.9 Subsequent ST elevation (STEMI) myocardial infarction of unspecified site

Billable ICD-10-CM code, FY2026. Acts as a Major Complication or Comorbidity (MCC) as a secondary diagnosis.

Applicable to

• Subsequent acute myocardial infarction of unspecified site
• Subsequent myocardial infarction (acute) NOS

Applies from I22 Subsequent ST elevation (STEMI) and non-ST elevation (NSTEMI) myocardial infarction

Includes

• acute myocardial infarction occurring within four weeks (28 days) of a previous acute myocardial infarction, regardless of site
• cardiac infarction
• coronary (artery) embolism
• coronary (artery) occlusion
• coronary (artery) rupture
• coronary (artery) thrombosis
• infarction of heart, myocardium, or ventricle
• recurrent myocardial infarction
• reinfarction of myocardium
• rupture of heart, myocardium, or ventricle
• subsequent type 1 myocardial infarction

Excludes1 (never code together)

• subsequent myocardial infarction, type 2 (I21.A1)
• subsequent myocardial infarction of other type (type 3) (type 4) (type 5) (I21.A9)

Use additional code

• code, if applicable, to identify:
• exposure to environmental tobacco smoke (Z77.22)
• history of tobacco dependence (Z87.891)
• occupational exposure to environmental tobacco smoke (Z57.31)
• status post administration of tPA (rtPA) in a different facility within the last 24 hours prior to admission to current facility (Z92.82)
• tobacco dependence (F17.-)
• tobacco use (Z72.0)

Risk adjustment (HCC)

• CMS-HCC V28: HCC 228 — Acute Myocardial Infarction
• CMS-HCC V22: HCC 86 — Acute Myocardial Infarction
• RxHCC V08: HCC 188 — Coronary Artery Disease
• ESRD V24: HCC 86

MS-DRG index

Defines the logic of DRG(s) 280-285 in MDC 05.

Approximate ICD-9-CM (GEMs)

• 410.91 Acute myocardial infarction of unspecified site, initial episode of care (approximate)

Code annotations containing back-references to I22.9

Back-references to I22

• Type 2 Excludes: I21 Acute myocardial infarction ("subsequent type 1 myocardial infarction (I22.-)")
• Type 1 Excludes: I25.82 Chronic total occlusion of coronary artery ("acute coronary occlusion with myocardial infarction (I21.0-I21.B, I22.-)")
• Type 2 Excludes: I74 Arterial embolism and thrombosis ("coronary embolism and thrombosis (I21-I25)")
• Type 2 Excludes: I82 Other venous embolism and thrombosis ("coronary (I21-I25)")
• Code First: Z92.82 Status post administration of tPA (rtPA) in a different facility within the last 24 hours prior to admission to current facility ("acute myocardial infarction (I21.-, I22.-)")

Diagnosis Index entries for I22.9

• Infarct, infarction › myocardium, myocardial (acute) (with stated duration of 4 weeks or less) › ST elevation (STEMI) › subsequent
• Infarct, infarction › myocardium, myocardial (acute) (with stated duration of 4 weeks or less) › subsequent (recurrent) (reinfarction)
• Infarct, infarction › myocardium, myocardial (acute) (with stated duration of 4 weeks or less) › subsequent (recurrent) (reinfarction) › ST elevation
• Infarct, infarction › myocardium, myocardial (acute) (with stated duration of 4 weeks or less) › subsequent (recurrent) (reinfarction) › transmural
• Infarct, infarction › myocardium, myocardial (acute) (with stated duration of 4 weeks or less) › subsequent (recurrent) (reinfarction) › type 1

Nearby codes

• I22 Subsequent ST elevation (STEMI) and non-ST elevation (NSTEMI) myocardial infarction
• I22.0 Subsequent ST elevation (STEMI) myocardial infarction of anterior wall
• I22.1 Subsequent ST elevation (STEMI) myocardial infarction of inferior wall
• I22.2 Subsequent non-ST elevation (NSTEMI) myocardial infarction
• I22.8 Subsequent ST elevation (STEMI) myocardial infarction of other sites
• I22.9 Subsequent ST elevation (STEMI) myocardial infarction of unspecified site (this code)