The determination of the epidemiology of myocarditis and ICMP is complicated as a result of a lot of factors including primarily challenging diagnosis lacking for now in a single test which would provide sufficient specificity and sensitivity for the unequivocal determination of myocarditis, and also because of the varied course and manifestation because of what mild forms of myocarditis do not have to be diagnosed.
Epidemiological studies are thus facing a number of limitations. A certain proof of myocarditis or ICMP is gained primarily with the endomyocardial biopsy (EMB). However, the evaluation of EMB samples was in some researches performed just on the grounds of the Dallas criteria which are not sufficient enough for the diagnosis of myocarditis according to some references [42, 140]. The main limitation is considered primarily a low test sensitivity and relatively high demands for the experiences of an expert evaluating the results.
Based on the Finnish epidemiological study from 1970´s and 1980´s, incidence of myocarditis was 0,17 cases per 1000 inhabitants per year [6]. The post-mortem EMB incidence of myocarditis in a Swedish study from Malmö was 1,06 % [7].
In Myocarditis Treatment Trial study, myocarditis was diagnosed on the grounds of the histopathological criteria in 10 % of performed EMBs [11]. It also concluded information about mortality of patients with myocarditis and the necessity of heart transplant. Study included 111 patients, 34 of them died and 10 underwent heart transplant. The mortality in the 4th year of the study was even more than 50 %. Other resources report about a high mortality and necessity of heart transplant primarily in paediatric patients where the average mortality and heart transplant necessity is around 30 % [12]. At the same time, this number increases in infants, reaching in the case of new-borns up to 75% mortality rate [13]. In the present, the incidence of myocarditis in Europe is considered approximately 131 cases per 1 million inhabitants per year [8].
Based on Global Burden of Disease study, over 2,5 million cases of myocarditis and cardiomyopathies was reported worldwide in 2015 including 156 thousand cases of acute myocarditis. Moreover, both groups reported over 20% increase of cases when comparing with 2005 [89].
Myocarditis is considered as a cause of sudden cardiac death, primarily in young individuals, in 9 to 20 % [14,15], based on bioptically taken samples of the myocardium. However, some studies have found signs of myocarditis bioptically in up to 42 % of cases [9].
Myocarditis very significantly contributes to the development of the dilated cardiomyopathy (DCMP). It is stated that its part in the development of the DCMP is around 20 %, however an American study which pursued the identification of causes of the DCMP in children, confirmed the diagnosis of myocarditis in 46 % of cases [10].
The representation of myocarditis in the development of heart failure varies from 0,5 to 4 % [30].
The results of these and other studies thus make myocarditis the most frequent aetiology of the DCMP and so it is ICMP [99].
Author of the opening picture: vlastní zdroj
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References:
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7) GRAVANIS, M.B. a N.H. STERNBY. Incidence of myocarditis. A 10-year autopsy study from Malmö, Sweden. Arch Pathol Lab Med [online]. 1991, 115(4), 390-392 [cit. 2016-09-02].
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30) COOPER JR., L.T., A. KEREN a et al. The Global Burden of Myocarditis: Part 1: A Systematic Literature Review for the Global Burden of Diseases, Injuries, and Risk Factors 2010 Study. Global Heart. 2014, 9(1), 121-129.
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