I21.19ST elevation (STEMI) myocardial infarction involving other coronary artery of inferior wall

I21.19 is the ICD-10-CM diagnosis code for ST elevation (STEMI) myocardial infarction involving other coronary artery of inferior wall. It belongs to category I21 (acute myocardial infarction), block I20-I25 (ischemic heart diseases) and chapter 9 (diseases of the circulatory system). It is billable, so it can be reported on its own for dates of service from October 1, 2026 through September 30, 2027.

Within I21.1, choose I21.19 (other coronary artery of inferior wall) only when documentation doesn't support a more specific option: right coronary artery (I21.11).

The conditions in its Excludes2 note aren't part of I21.19, but may be coded alongside it if the patient has both: ST elevation (STEMI) myocardial infarction involving left circumflex coronary artery (I21.21).

Use an 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.-) and 1 more.

As a secondary diagnosis it is an MCC (major complication or comorbidity), which can move an inpatient stay into the highest-paying "with MCC" MS-DRG of its family, unless the principal diagnosis excludes it.

In MS-DRG v44.0, it is part of the grouping logic for DRG 280 (Acute Myocardial Infarction, Discharged Alive with MCC, relative weight 1.6112), DRG 281 (Acute Myocardial Infarction, Discharged Alive with CC, relative weight 0.9184), DRG 282 (Acute Myocardial Infarction, Discharged Alive without CC/MCC, relative weight 0.7378), DRG 283 (Acute Myocardial Infarction, Expired with MCC, relative weight 1.9619), DRG 284 (Acute Myocardial Infarction, Expired with CC, relative weight 0.7525) and DRG 285 (Acute Myocardial Infarction, Expired without CC/MCC, relative weight 0.539), in MDC 05 (Diseases and Disorders of the Circulatory System), as a principal or secondary diagnosis. The DRG a claim lands in depends on the principal diagnosis, procedures and any CC/MCC secondary diagnoses.

It has been part of ICD-10-CM since the code set took effect on October 1, 2015 and hasn't changed since.

Before ICD-10, this condition was coded in ICD-9-CM as 410.21 (acute myocardial infarction of inferolateral wall, initial episode of care) and 410.41 (acute myocardial infarction of other inferior wall, initial episode of care).