Myocarditis is an inflammatory disease of the myocardium of the focal or diffuse characteristic caused primarily by a viral agent. It is a condition with a varied manifestation and course including asymptomatic cases, new-onset dilated cardiomyopathy, heart arrhythmias, heart failure, cardiogenic shock or sudden death. There is not a unanimous definition of myocarditis and inflammatory cardiomyopathy considering their different evaluating criteria.
According to the WHO 1995 definition, ICMP is defined as “myocarditis connected with the cardiac dysfunction [1],” and at the same time myocarditis is defined as “an inflammatory disease of the myocardium diagnosed by established histological, immunological and immunohistochemical methods.”
In 2008, ICMP was classified in the classification of cardiomyopathies of the European Society of Cardiology to dilated cardiomyopathies and it is defined by “the presence of chronic inflammatory cells in the myocardium in association with the left ventricular dilatation and reduced ejection fraction.” Dilated cardiomyopathy is according to the same classification defined by “the presence of the left ventricular dilatation and left ventricular systolic dysfunction in the absence of abnormal loading conditions (hypertension, valve disease) or coronary artery disease sufficient to cause global systolic impairment.” [2]
According to histological criteria, specifically according to Dallas criteria, the diagnosis of myocarditis is confirmed by “the presence of the inflammatory infiltrate of the myocardium with the degeneration or necrosis of cardiomyocytes of non-ischemic characteristic [3]”. However, up to the present, these criteria are not always sufficient enough for example to the effect that they do not have to correspond with the clinical course of the disease [4]. According to the immunohistochemical analysis, which is preferred at present, myocarditis is diagnosed by the “presence of ≥ 14 leukocytes per mm² of the bioptically removed myocardium samples, including up to 4 monocytes or macrophages per mm² and ≥ 7 CD3+ T-lymphocytes per mm²” [5].
Author of the opening picture: Wapcaplet, Yaddah, Wnauta
————————————————————————————————————————————————————————————————————————————–
References:
1) RICHARDSON P., MCKENNA W., BRISTOW M., MAISCH B., MAUTNER B., O´CONNELL J., OLSEN E., THIENE G., GOODWIN J., GYARFAS I., MARTIN I., NORDER P. Report of the 1995 World Health Organization/International Society and Federation of Cardiology Task Force on the Definition and Classification of Cardiomyopathies. Circulation, 93(5), 841–842.
2) ELLIOTT P., ANDERSSON B., ARBUSTINI E., BILINSKA Z., CECCHI F., CHARRON P., DUBOURG O., KÜHL U., MAICH B., MCKENNA W.J., MOSERRAT L., PANKUWEIT S., RAPEZZI C., SEFEROVIC P., TAVAZZI L., KEREN A. Classification of the cardiomyopathies: a position statement from the European society of cardiology working group on myocardial and pericardial diseases. European Heart Journal [online]. 2008, -(29), 270–276 [cit. 2016-08-10].
3) T., ARETZ et al. Myocarditis. A histopathologic definition and classification. The American Journal of Cardiovascular Pathology [online]. 1986, 1(1), 3-14 [cit. 2017-02-06].
4) AL-AQEEDI R.F., Chapter 2: Clinical Presentation. In: WILSON J. Clinical Handbook of Myocarditis. New Jersey: Foster Academics, 2015. pp. 33–69. ISBN: 978-1-63242-083-1.
5) MAISCH B., BÜLTMAN B., FACTOR S., GRÖNE H.-J. et al. World Heart Federation Consensus Conferences Definition of Inflammatory Cardiomyopathy (Myocarditis): Report from two Expert Committees on Histology and Viral Cardiomyopathy. Herz [online]. 2000, 25 (3), 200-209 [cit. 2016-08-26].
