Myocarditis classification
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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1] Associate Editor(s)-In-Chief: Varun Kumar, M.B.B.S. Maliha Shakil, M.D. [2]
Overview
Myocarditis may be classified according to pathologic findings into 4 subtypes: fulminant myocarditis, acute myocarditis, chronic active myocarditis, and chronic persistent myocarditis.
Classification
- Myocarditis can be classified based on the causative, histological, and clinicopathological criteria.
- The causative criteria define infectious agents (virus, protozoa, or bacteria) or non-infectious condition (autoimmune diseases, medications etc.) associated with myocarditis.
- Identification of the infectious agent or potential non-infectious trigger may be indicative not only for disease etiology.
- In addition to identification of the causative agent, histological and immunohistological analyses are performed to categorize myocarditis based on the presence, morphology and type of inflammatory infiltrates in the myocardium.
- Lymphocytic myocarditis characterized by extensive infiltration of lymphocytes and monocytes with signs of cardiomyocyte necrosis (active lymphocytic myocarditis) represents the most frequent type of myocarditis.
- Lymphocytic myocarditis is often observed in myocardium tested positive for viral persistence.
- Less common forms of myocarditis represent giant cell myocarditis and eosinophilic myocarditis.
- Giant cell myocarditis is characterized by the presence of multinucleated giant cells and lymphocytes on heart biopsies.
- Presence of giant cells within non-caseating granulomas, usually associated with myocardial fibrosis is referred to as cardiac sarcoidosis.
- The characteristic feature of eosinophilic myocarditis is the presence of eosinophil-rich infiltrates in the myocardium and extensive myocyte necrosis, which is accompanied with elevated level of circulating eosinophils.
- Giant cell myocarditis and eosinophilic myocarditis are associated with particularly poor prognosis.
Clinicopathological criteria
- Fulminant myocarditis: Fulminant myocarditis occurs following a viral prodrome. Fulminant myocarditis presents as acute severe cardiovascular compromise with ventricular dysfunction.[1][2] On endomyocardial biopsy, there are multiple foci of inflammation.
- Acute myocarditis: Acute myocarditis presents with a less distinct onset of the illness. When the patient does present, there is already a decline in left ventricular dysfunction. Acute myocarditis may progress to dilated cardiomyopathy.
- Chronic active myocarditis: Chronic active myocarditis has a less distinct onset of the illness. There are clinical and histologic relapses and the development of ventricular dysfunction. Histologically, chronic inflammatory changes with mild to moderate fibrosis may be present.
- Chronic persistent myocarditis: Chronic persistent myocarditis has a less distinct onset of the illness. Histologically it is characterized by persistent infiltration and myocyte necrosis. Despite the presence of symptoms, ventricular dysfunction is absent.
==Causative criteria== Clinicopathological criteria Virus: coxsackievirus B3, adenoviruses or herpesviruses and other Protozoa: Trypanosoma cruzi (Chagas disease) Bacteria: Borrelia burgdorferi (Lyme disease) and other Immune checkpoint inhibitors: anti-CTLA-4, anti-PD-1 or anti-PD-L1 therapy Systemic autoimmune diseases: Systemic lupus erythematosus, myasthenia gravis and other
Histological criteria
- Active myocarditis: cardiac inflammation with apparent cardiomyocyte necrosis
- Borderline myocarditis: cardiac inflammation without evident cardiomyocyte necrosis
- Lymphocytic myocarditis: extensive infiltration of lymphocytes and monocytes
- Giant cell myocarditis: multinucleated giant cells and lymphocytes on heart biopsies
- Eosinophilic myocarditis: eosinophil-rich infiltrates with extensive myocyte necrosis
References
- ↑ Lieberman EB, Hutchins GM, Herskowitz A, Rose NR, Baughman KL (1991). "Clinicopathologic description of myocarditis". J Am Coll Cardiol. 18 (7): 1617–26. PMID 1960305.
- ↑ McCarthy RE, Boehmer JP, Hruban RH, Hutchins GM, Kasper EK, Hare JM; et al. (2000). "Long-term outcome of fulminant myocarditis as compared with acute (nonfulminant) myocarditis". N Engl J Med. 342 (10): 690–5. doi:10.1056/NEJM200003093421003. PMID 10706898.