Streptolysin O and possible streptococcal wall fragments appear to be responsible. In fatal cases, the histopathologic evaluation revealed necrosis of muscular fibers and a mononuclear cell reaction resembling acute viral myocarditis. Although the pathogenic relationship between acute streptococcal tonsillitis and concurrent acute streptococcal myocarditis is rather obscure, lymphatic connections between the tonsils and the heart seem to be responsible
implicated