Myocarditis may present with a wide range of symptoms, ranging from mild dyspnea or chest pain that resolves without specific therapy to cardiogenic shock and death. Dilated cardiomyopathy with chronic heart failure is the major long-term sequela of myocarditis. Most often, myocarditis results from common viral infections; less commonly, specific forms of myocarditis may result from other pathogens, toxic or hypersensitivity drug reactions, giant-cell myocarditis, or sarcoidosis.
- Active myocarditis: the presence of an inflammatory infiltrate of the myocardium with necrosis and/or degeneration of adjacent myocytes not typical of the ischaemic damage associated with coronary artery disease (CAD).
- Borderline myocarditis: the presence of an inflammatory infiltrate of the myocardium without necrosis or degeneration of adjacent myocytes.
World Health Organization Marburg Classification
- Acute (active) myocarditis: a clear-cut infiltrate (diffuse, focal or confluent) of >14 leukocytes/mm2 (preferably activated T cells). The amount of the infiltrate should be quantified by immunohistochemistry. Necrosis or degeneration is compulsory; fibrosis may be absent or present and should be graded.
- Chronic myocarditis: an infiltrate of >14 leukocytes/mm2 (diffuse, focal or confluent, preferably activated T cells). Quantification should be made by immunohistochemistry. Necrosis or degeneration is usually not evident; fibrosis may be absent or present and should be graded.
- No myocarditis: No infiltrating cells or <14 leukocytes/mm2.
- Ongoing (persistent) myocarditis. Criteria as in acute or chronic myocarditis.
- Resolving (healing) myocarditis. Criteria as in acute or chronic myocarditis, but the immunologic process is sparser than in the first biopsy.
- Resolved (healed) myocarditis. Corresponds to the Dallas classification.
The amount and distribution of fibrosis should be described similarly as no (grade 0), mild (grade 1), moderate (grade 2) or severe (grade 3). Localisation or formation of fibrosis should be outlined as endocardial, replacement or interstitial.
Expanded criteria for diagnosis of myocarditis
- Suspicious for myocarditis = 2 positive categories
- Compatible with myocarditis = 3 positive categories
- High probability of being myocarditis = all 4 categories positive.
NOTE: Any matching feature in category = positive for category
Category I: clinical symptoms
- Clinical heart failure
- Viral prodrome
- Dyspnoea on exertion
- Chest pain
- Pre-syncope or syncope
Category II: evidence of cardiac structural/functional perturbation in the absence of regional coronary ischaemia
- Echo evidence
- Regional wall motion abnormalities
- Cardiac dilation
- Regional cardiac hypertrophy
- Troponin release
- Troponin result has high sensitivity (>0.1 nanogram/mL)
- Positive indium-111 antimyosin scintigraphy and normal coronary angiography or absence of reversible ischaemia by coronary distribution on perfusion scan
Category III: cardiac MRI
- Increased myocardial T2 signal on inversion recovery sequence
- Delayed contrast enhancement following gadolinium-diethylenetriamine pentaacetic acid (DTPA) infusion.
Category IV: myocardial biopsy, pathologic or molecular analysis
- Pathology findings compatible with Dallas criteria
- Presence of viral genome by PCR or in situ hybridisation.
- Aretz HT, Billingham ME, Edwards WD, Factor SM, Fallon JT, Fenoglio JJ Jr, Olsen EG, Schoen FJ. Myocarditis. A histopathologic definition and classification. Am J Cardiovasc Pathol. 1987 Jan;1(1):3-14. [Medline]
- Richardson P, McKenna W, Bristow M, Maisch B, Mautner B, O’Connell J, Olsen E, Thiene G, Goodwin J, Gyarfas I, Martin I, Nordet P. Report of the 1995 World Health Organization/International Society and Federation of Cardiology Task Force on the Definition and Classification of cardiomyopathies. Circulation. 1996 Mar 1;93(5):841-2. [Medline]
- Cooper LT Jr. Myocarditis. N Engl J Med. 2009 Apr 9;360(15):1526-38. [Medline]
Created: Apr 10, 2009