Heart & vascular pathology

Inflammatory disease

Noninfective myocarditis

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Last staff update: 31 December 2020

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PubMed Search: Noninfective myocarditis

R. Amita, M.D.
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Cite this page: Amita R. Noninfective myocarditis. PathologyOutlines.com website. https://www.pathologyoutlines.com/topic/heartnoninfecmyo.html. Accessed September 21st, 2023.
Definition / general
  • Myocarditis is an inflammatory disease of the myocardium caused by different infectious and noninfectious triggers
  • Non infectious types include lymphocytic, eosinophilic and giant cell myocarditis (GCM)
  • GCM has been termed idiopathic GCM, pernicious myocarditis, Fiedler myocarditis, acute idiopathic interstitial myocarditis, giant cell granulomatous myocarditis, and granulomatous myocarditis
  • Incidence difficult to determine as most cases are believed to be subclinical or underdiagnosed
  • Most cases of lymphocytic myocarditis are idiopathic
  • A primary autoimmune etiology has been suggested for GCM, based on the antimyosin GCM Lewis rat model and a high prevalence of associated autoimmune disorders, especially inflammatory bowel disease
Diagrams / tables

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Etiology of Myocarditis

Clinical features
  • Asymptomatic or nonspecific symptoms of chest pain, fever, sweats, chills, dyspnea
  • Palpitations, syncope or sudden cardiac death may develop because of underlying ventricular arrhythmias or atrioventricular block
  • In necrotizing eosinophilic myocarditis (NEC), a previously healthy patient experiences a rapid, acute progression to systolic failure and hemodynamic compromise which is usually fatal
  • Definitive diagnosis requires an endomyocardial biopsy
  • The Japanese Circulation Society Task Force Committee on Acute and Chronic Myocarditis published guidelines (Circ J 2011;75:734) for the diagnosis of eosinophilic myocarditis which includes eosinophilia > 500 / μL, cardiac symptoms, elevated cardiac enzymes, electrocardiogram (ECG) changes, and cardiac dysfunction on ultrasonography, especially in the setting of unremarkable coronary angiography
  • Radiology description
    • Features are similar to those described in infective myocarditis
    Radiology images

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    Transthoracic cardiac echocardiograms

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    Pericardial effusion of 1.2 cm

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    Subendocardial delayed enhancement

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    Increased septal wall thickness

    Prognostic factors
    • Most patients recover spontaneously with no known sequela
    • A small percentage of patients, mostly children and young adults, present with fulminant disease at onset and may progress rapidly to sudden death
    Case reports
    • Treatment of myocarditis includes supportive therapy for symptoms of acute heart failure and withdrawal of the offending agent, if applicable
    Gross description
    • Cardiac hypertrophy may be present with associated ventricular dilation
    • The affected myocardium may appear pale, sometimes with hemorrhagic foci
    Microscopic (histologic) description
    • Lymphocytic myocarditis:
      • A focal or diffuse lymphohistiocytic infiltrate (mostly T cell type) within myocardial fibers
      • Myocyte necrosis is typically present; interstitial fibrosis of varying degree is commonly seen
      • Presence of edema should not be used as a criterion for diagnosis of myocarditis
    • Giant cell myocarditis:
      • Diffuse infiltration of myocardium by a heterogeneous infiltrate composed of abundant lymphocytes, eosinophils, plasma cells and scattered prominent giant cells
      • There are no well defined granulomas
      • It has a more fulminant course (J Card Fail 2002;8:74, Semin Arthritis Rheum 2000;30:1)
    • Eosinophilic myocarditis:
      • Mixed inflammatory cell infiltrate consisting of many eosinophils with histiocytes, lymphocytes and plasma cells; myocardial necrosis is not common and interstitial fibrosis is typically absent or minimal
      • Eosinophilic myocarditis associated with hypereosinophilic syndrome is characterized by peripheral eosinophilia greater than 1,500 / μL over 6 months, without a known cause and with an indolent course (Can J Cardiol 2006;22:1233)
    • Hypersensitivity myocarditis (HSM):
      • Due to drug exposure; less necrosis, more prominent perivascular infiltrate, vasculitis and liver involvement
    • Necrotising eosinophilic myocarditis:
      • Extensive myocardial necrosis due to release of major basic protein from degranulated eosinophils
    • Sarcoid myocarditis:
    Microscopic (histologic) images

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    Acute myocarditis with lymphocytic infiltration

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    Endomyocardial biopsy

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    Eosinophilic infiltration

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    Necrotizing eosinophilic myocarditis

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    Eosinophilic myocarditis

    Virtual slides

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    Positive stains
    • CD3+ T lymphocytes, CD68+ histiocytes
    Additional references
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