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    v1.0.28
    OpenPayerBilling CodesOther forms of heart diseaseICD-10-CM i40-acute-myocarditis
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    ICD-10-CM Code For Acute Myocarditis: Group Overview

    The International Classification of Diseases, Tenth Revision, Clinical Modification (ICD-10-CM) code group I40 includes acute inflammatory disorders of the myocardium such as acute myocarditis due to infectious, autoimmune, or toxic causes, and specific subtypes like fulminant or unspecified myocarditis. These ICD-10-CM diagnosis codes are used to document acute presentations of myocardial inflammation, capturing severity, complications such as heart failure or arrhythmia, and organ involvement relevant to this group. Accurate coding within the ICD-10-CM I40 group supports proper claim adjudication, complete clinical documentation, and appropriate reimbursement.

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    ICD-10-CM I40: Acute Myocarditis Overview

    The acute myocarditis group covers inflammatory conditions of the heart muscle that may impair cardiac function and conduction. These diagnoses target the myocardium and are often related to infectious, autoimmune, or toxic etiologies. Accurate coding matters for reimbursement because it documents the severity and clinical complexity that affect resource use and claim adjudication.

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    When to Use

    Use a code from this group when a patient has a clinical diagnosis of acute myocarditis documented by treating clinicians, including cases with identified infectious, immune-mediated, or toxic causes. Apply specific subcategory codes when etiology or clinical subtype (for example, fulminant myocarditis) is documented to reflect severity and guide billing and documentation.

    ICD-10-CM Codes

    4 rows

    ICD-10-CM CodeDescription
    I40.0Infective myocarditis
    I40.1Isolated myocarditis
    I40.8Other acute myocarditis
    I40.9Acute myocarditis, unspecified

    DRG Codes

    8 rows

    DRG CodeDescription
    314Other Circulatory System Diagnoses with MCC
    315Other Circulatory System Diagnoses with CC
    316Other Circulatory System Diagnoses without CC/MCC
    791Prematurity with Major Problems
    793Full Term Neonate with Major Problems
    974HIV with Major Related Condition with MCC
    975HIV with Major Related Condition with CC
    976HIV with Major Related Condition without CC/MCC

    Typical Clinical Scenarios

    • A young adult presents to the emergency department with acute onset chest pain, fever, dyspnea, and recent viral prodrome; ECG shows diffuse ST-segment changes and cardiac enzymes are elevated, and cardiac MRI demonstrates myocardial inflammation consistent with acute myocarditis. Because the presentation is sudden and inflammatory, an acute myocarditis diagnosis from this group is assigned to capture the active inflammatory process. Typical codes: I40.0, I40.9
    • An older adult hospitalized with heart failure symptoms after a confirmed bacterial infection develops new systolic dysfunction on echocardiogram and is found to have myocardial inflammation on biopsy; the treating team documents a nonviral, acute myocarditis contributing to the decompensation. A code from this group is used to reflect myocarditis as the acute cardiac process complicating the hospitalization. Typical codes: I40.1, I40.8
    • A patient admitted to the coronary care unit with cardiogenic shock following recent symptom onset and high troponin levels is diagnosed with fulminant myocarditis after hemodynamic instability and arrhythmias necessitate inotropic support and close monitoring. The severe, rapidly progressive nature of the myocardial inflammation warrants assignment of an acute myocarditis code from this group to indicate the life-threatening acute condition. Typical codes: I40.0, I40.9

    Related Codes

    I30-ACUTE-PERICARDITIS

    ICD-10-CM Code For Acute Pericarditis: Group Overview

    I31-OTHER-DISEASES-OF-PERICARDIUM

    ICD-10-CM Code For Other Diseases Of Pericardium: Group Overview

    I32-PERICARDITIS-IN-DISEASES-CLASSIFIED-ELSEWHERE

    ICD-10-CM Code For Pericarditis In Diseases Classified Elsewhere: Group Overview

    I33-ACUTE-AND-SUBACUTE-ENDOCARDITIS

    ICD-10-CM Code For Acute And Subacute Endocarditis: Group Overview

    I34-NONRHEUMATIC-MITRAL-VALVE-DISORDERS

    ICD-10-CM Code For Nonrheumatic Mitral Valve Disorders: Group Overview

    I35-NONRHEUMATIC-AORTIC-VALVE-DISORDERS

    ICD-10-CM Code For Nonrheumatic Aortic Valve Disorders: Group Overview

    I36-NONRHEUMATIC-TRICUSPID-VALVE-DISORDERS

    ICD-10-CM Code For Nonrheumatic Tricuspid Valve Disorders: Group Overview

    I37-NONRHEUMATIC-PULMONARY-VALVE-DISORDERS

    ICD-10-CM Code For Nonrheumatic Pulmonary Valve Disorders: Group Overview

    I38-ENDOCARDITIS-VALVE-UNSPECIFIED

    ICD-10-CM Code For Endocarditis Valve Unspecified: Group Overview

    I39-ENDOCARDITIS-AND-HEART-VALVE-DISORDERS

    ICD-10-CM Code For Endocarditis And Heart Valve Disorders In Diseases Classified Elsewhere: Group Overview

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    Frequently Asked Questions

    References

    1. 1.CPT® Codes and Descriptions. AAPC. Retrieved Aug 11, 2026.Maintains the CPT code set's official descriptions and guidelines, licensed from the American Medical Association, used as the definitional source for CPT codes on this page.
    2. 2.HCPCS Quarterly Update. Centers for Medicare & Medicaid Services (CMS). Retrieved Aug 11, 2026.CMS's quarterly release of HCPCS Level II codes and short/long descriptors, the source for HCPCS code definitions and update history.
    3. 3.ICD-10-CM Full Code List. Centers for Medicare & Medicaid Services (CMS). Retrieved Aug 11, 2026.CMS's complete ICD-10-CM diagnosis code list, used to cross-reference diagnosis codes associated with this procedure or service.
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