View of transverse section of heart from above.
Anterior surface faces upwards, thick left ventricle on the left, right ventricle on right.
This is due to a dense interstitial infiltrate of inflammatory cells. The normal appearing red myocardium elsewhere could also show microscopic infiltrates, which are not dense enough to see grossly. Cardiotropic organisms, mostly viral, are blood borne. Inflammatory response is to the organisms and necrotic muscle. Postinfectious immunogenic cases may be due to complexing of antigenic products of organisms with tissues, or cross reacting determinants common to both organism and host tissues.