Billing Status: YES. This is a valid, specific, and billable ICD-10-CM reference.

Inpatient Payment Groups (MS-DRG)

MS-DRGs this diagnosis helps define, as principal or secondary, per the CMS ICD-10-CM/PCS MS-DRG Definitions Manual v43.0 (FY2026), Appendix B.

MS-DRG 280 — ACUTE MYOCARDIAL INFARCTION, DISCHARGED ALIVE WITH MCC (MDC 05)
MS-DRG 281 — ACUTE MYOCARDIAL INFARCTION, DISCHARGED ALIVE WITH CC (MDC 05)
MS-DRG 282 — ACUTE MYOCARDIAL INFARCTION, DISCHARGED ALIVE WITHOUT CC/MCC (MDC 05)
MS-DRG 283 — ACUTE MYOCARDIAL INFARCTION, EXPIRED WITH MCC (MDC 05)
MS-DRG 284 — ACUTE MYOCARDIAL INFARCTION, EXPIRED WITH CC (MDC 05)
MS-DRG 285 — ACUTE MYOCARDIAL INFARCTION, EXPIRED WITHOUT CC/MCC (MDC 05)

A diagnosis appearing in a group's logic does not by itself determine the DRG assigned to a stay; the grouper uses the full claim.

Risk Adjustment (CMS-HCC)

Payment categories this diagnosis maps to under CMS-HCC V28, payment year 2026.

Other models: CMS-HCC V22 HCC 86 · RxHCC V08 HCC 188

Risk scores depend on the enrollee's full accepted diagnosis set and segment; a category mapping alone does not determine payment.

Code Set: Valid FY2026 and FY2027. FY2026 took effect October 1, 2025.

ST elevation (STEMI) myocardial infarction involving right coronary artery is a billable ICD-10-CM diagnosis code (I21.11).

Sequencing, inclusion, and exclusion notes published for I21.11 in the official ICD-10-CM tabular list.

Conditions the official ICD-10-CM tabular list includes under this code.

cardiac infarction
coronary (artery) embolism
coronary (artery) occlusion
coronary (artery) rupture
coronary (artery) thrombosis
infarction of heart, myocardium, or ventricle
myocardial infarction specified as acute or with a stated duration of 4 weeks (28 days) or less from onset

Alternative terms the tabular list files under this code.

Conditions not covered by this code, but which may be reported alongside it when both are present.

Additional codes that may be required to fully describe the encounter.

Supplementary codes the tabular list directs you to add.

Use additional 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)

Official ICD-10-CM classifications closest to I21.11 in its code family, with their registry titles.

I21.0 — ST elevation (STEMI) myocardial infarction of anterior wall
I21.01 — ST elevation (STEMI) myocardial infarction involving left main coronary artery
I21.02 — ST elevation (STEMI) myocardial infarction involving left anterior descending coronary artery
I21.09 — ST elevation (STEMI) myocardial infarction involving other coronary artery of anterior wall
I21.1 — ST elevation (STEMI) myocardial infarction of inferior wall
I21.19 — ST elevation (STEMI) myocardial infarction involving other coronary artery of inferior wall
I21.2 — ST elevation (STEMI) myocardial infarction of other sites
I21.21 — ST elevation (STEMI) myocardial infarction involving left circumflex coronary artery
I21.29 — ST elevation (STEMI) myocardial infarction involving other sites
I21.3 — ST elevation (STEMI) myocardial infarction of unspecified site

Clinical term phrases from the official ICD-10-CM Index to Diseases and Injuries that map to this code.

Infarct, infarction, myocardium, myocardial (acute) (with stated duration of 4 weeks or less), ST elevation (STEMI), inferoposterior transmural (Q wave)
Infarct, infarction, myocardium, myocardial (acute) (with stated duration of 4 weeks or less), ST elevation (STEMI), involving, right coronary artery
Infarct, infarction, myocardium, myocardial (acute) (with stated duration of 4 weeks or less), transmural (see also, Infarct, myocardium, ST elevation, by site), inferoposterior (Q wave)