Myocarditis

Overview
  • Myocarditis refers processes of cardiac injury which are primarily the result of cardiac inflammation
Etiologies
  • Overview
    • In most cases, myocarditis results from microbial infection of the myocardium, typically of viral origin. Myocardial damage due to infections can be the result of direct microbial damage as well as immune-mediated injury associated with the inflammatory response. Although less common, several autoimmune processes can also result in inflammation-mediated myocardial injury. In general, the histomorphology of the affected cardiac tissue is dependent on the particular etiology.
  • Viral Etiologies
    • A variety of viruses can result in myocarditis although Group B Coxsackie Viruses are by far the most common. Acute viral myocarditis is usually associated with a lymphocytic inflammatory infiltrate.
  • Parasitic Etiologies
    • Infection with Trypanosoma cruzi results in Chagas Disease. Parasites are often visible histologically.
  • Bacterial Etiologies
    • Isolated bacterial myocarditis is uncommon although extension from adjacent loci of bacterial infective endocarditis is possible. Lyme myocarditis can occur during the acute phase of infection with Borrelia burgdorferi. Diphtheritic myocarditis is likely due to damage caused by diptheria toxin produced by distant foci of Corynebacterium diptheriae infection. Bacterial infection of the myocardium is generally characterized by a strongly neutrophilic infiltrate.
  • Autoimmune Etiologies
Clinical Consequences
  • In most cases, Viral Myocarditis is usually heralded by traditional constitutional symptoms associated with infection such as fever. In most cases myocarditis is subclinical, rapidly resolves, and is self-limited. However, when fulminant infection arises, the patient can develop arrhythmias or their cardiac function can rapidly deteriorate resulting in signs and symptomology associated with acute heart failure. If milder infections do not resolve, long-term inflammation can lead to cardiac remodeling and the development of a morphological picture of dilated cardiomyopathy with attendant congestive heart failure.