Myocarditis

Myocarditis is the term used to indicate acute infective, toxic or autoimmune inflammation of the heart. Reversible toxic myocarditis occurs in diphtheria and sometimes in infective endocarditis when autoimmune mechanisms may also contribute. Persistent viral infection of the myocardium was first demonstrated a decade ago.1 Slow growing organisms such as chlamydia and trypanosomal infection in Chagas' disease are causes of chronic myocarditis. Non-infective causes in sarcoidosis and the collagen vascular diseases need to be sought.

Acute myocarditis and acute pericarditis are not always associated (likewise meningitis and encephalitis do not always occur together) and the clinical emphasis is usually on one or the other.

Myocarditis can be caused by many different viruses and the microbial pathogenesis may be complex. Most cases of myocarditis with onset in otherwise healthy people probably have an infectious origin, although the pathogenesis is not yet fully understood (such as the finding of a link between chlamydia and heart disease through antigenic mimicry). In western countries enteroviruses, especially coxsackie B 1–6 serotypes, are the most frequent, and the recent identification of a common coxsackie virus B and adenovirus receptor has explained why these very different virus types both cause myocarditis.2-4