{"code":"I21.3","type":"code","title":"ST elevation (STEMI) myocardial infarction of unspecified site","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","I21.21","I21.29","I21.4","I21.9","I21.A","I21.A1","I21.A9","I21.B"],"inclusionTerms":["Acute transmural myocardial infarction of unspecified site","Transmural (Q wave) myocardial infarction NOS","Type 1 ST elevation myocardial infarction of unspecified site"],"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 of unspecified site is a billable ICD-10-CM diagnosis code (I21.3). 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 of unspecified site is a billable ICD-10-CM diagnosis code (I21.3). 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: Acute transmural myocardial infarction of unspecified site; Transmural (Q wave) myocardial infarction NOS; Type 1 ST elevation myocardial infarction of unspecified site. 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":""}