ICD-10-CM > I00-I99 > I20-I25 > I21 > I21.2 > I21.21 I21.21 ST elevation (STEMI) myocardial infarction involving left circumflex coronary artery Billable/Specific Copy Code Copy Description Applicable To ST elevation (STEMI) myocardial infarction involving oblique marginal coronary artery