{"code":"I21.21","type":"code","title":"ST elevation (STEMI) myocardial infarction involving left circumflex coronary artery","codeAlso":["the presence of hypertension (I10-I1A)"],"includes":["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"],"modern_v":"official26","codeFirst":[],"excludes1":[],"excludes2":["old myocardial infarction (I25.2)","postmyocardial infarction syndrome (I24.1)","subsequent type 1 myocardial infarction (I22.-)"],"isBillable":true,"fyEffectivity":{"fy2026":true,"fy2027":true,"billableFy2026":true,"billableFy2027":true},"sibling_codes":["I21","I21.0","I21.01","I21.02","I21.09","I21.1","I21.11","I21.19","I21.2","I21.29","I21.3","I21.4","I21.9","I21.A","I21.A1","I21.A9","I21.B"],"inclusionTerms":["ST elevation (STEMI) myocardial infarction involving oblique marginal coronary artery"],"sibling_titles":{"code":"I21.B","title":"Myocardial infarction with coronary microvascular dysfunction","isBillable":true},"useAdditionalCode":["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)"],"clinicalDefinition":"ST elevation (STEMI) myocardial infarction involving left circumflex coronary artery is a billable ICD-10-CM diagnosis code (I21.21). Includes: 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.","officialDefinition":"ST elevation (STEMI) myocardial infarction involving left circumflex coronary artery is a billable ICD-10-CM diagnosis code (I21.21). Includes: 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. Inclusion terms: ST elevation (STEMI) myocardial infarction involving oblique marginal coronary artery. Excludes2 (not included here): old myocardial infarction (I25.2); postmyocardial infarction syndrome (I24.1); subsequent type 1 myocardial infarction (I22.-). 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). Code also: the presence of hypertension (I10-I1A).","seventhCharacterInstructions":[],"workflowProtocols":[],"guidelines":{"whenToUse":[],"whenNotToUse":[],"commonBillingMistakes":[],"codeComparisons":[],"documentationChecklist":[]},"domainLandscape":{"summary":"Primary diagnostic domain and clinical landscape evaluation.","keyCategories":[],"diagnosticContinuum":"Progression continuum from acute presentation to resolution."},"children":[],"hierarchy":[],"relatedCodes":[],"relevantCPTCodes":[],"documentationTips":[],"caseStudies":[],"description":"","overview":"","noteProvenance":{"old myocardial infarction (I25.2)":"I21","postmyocardial infarction syndrome (I24.1)":"I21","subsequent type 1 myocardial infarction (I22.-)":"I21","code, if applicable, to identify:":"I21","exposure to environmental tobacco smoke (Z77.22)":"I21","history of tobacco dependence (Z87.891)":"I21","occupational exposure to environmental tobacco smoke (Z57.31)":"I21","status post administration of tPA (rtPA) in a different facility within the last 24 hours prior to admission to current facility (Z92.82)":"I21","tobacco dependence (F17.-)":"I21","tobacco use (Z72.0)":"I21","cardiac infarction":"I21","coronary (artery) embolism":"I21","coronary (artery) occlusion":"I21","coronary (artery) rupture":"I21","coronary (artery) thrombosis":"I21","infarction of heart, myocardium, or ventricle":"I21","myocardial infarction specified as acute or with a stated duration of 4 weeks (28 days) or less from onset":"I21","Type 1 ST elevation myocardial infarction of other sites":"I21.2"},"hcc":{"mapped":true,"model":"CMS-HCC V28","paymentYear":"2026","categories":[{"hcc":"228","label":"Acute Myocardial Infarction","family":"Heart","suppresses":[{"hcc":"229","label":"Unstable Angina and Other Acute Ischemic Heart Disease"}]}],"otherModels":[{"model":"CMS-HCC V22","hcc":"86"},{"model":"RxHCC V08","hcc":"188"}]}}