Aetiology of Acute myocarditis:
Several infectious and non-infectious diseases can cause myocarditis.
In the western world, the most common cause is viral infections. The predominant viral cause of this disease seems to change every decade (Coxsackie in the 1980s, adenovirus in the 1990s, and parvovirus B19 since 2000). PCR analysis of viral genomes in myocardial tissue from endomyocardial biopsy samples has now replaced viral culture and serial serological testing.
Autoimmune and systemic diseases may also rarely cause acute myocarditis.
Most patients recover, but a subset has progression to a second phase, consisting of an adaptive immune response. In this response, antibodies to viral proteins and to some cardiac proteins (including cardiac myosin and β1 or muscarinic receptors) are produced, and effector T cells proliferate. Eventually, the immune response is downregulated, and fibrosis replaces a cellular infiltrate in the myocardium, and may lead to chronic cardiomyopathy.