10th May 2025

Epidemiology

Myocarditis is likely underdiagnosed however, the number of UK hospital admissions is rising – 0.04% (36.5 per 100,000) of all hospital admissions in England between 1998 and 20172. The clinical features can be varied and frequently overlap and mimic other acute cardiac conditions, accounting for the variability in accurate diagnosis. 

It can affect all age groups, though the median age is slightly younger in men (33) compared to women (48) and there is a slightly higher prevalence in men than women (3:1).

There appears to be immunogenetic susceptibility in combination with an environmental trigger, e.g. infection, most commonly viral illness and patients are particularly susceptible if they have a viral co-infection.

It may present in acute, fulminant, subacute or chronic forms. Acute is diagnosed as less than one month between symptom onset and diagnosis. Fulminant is severe and associated with cardiogenic shock, often requiring inotropes or mechanical circulatory support. Subacute is considered to be either persistent or recurrent myocarditis, or healing myocarditis where there is evidence of previous myocardial inflammation. It is defined as between 1-3 months between symptoms onset and diagnosis. Chronic is diagnosed when symptoms persist for more than one month.