Myocarditis

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Myocarditis

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Infectious agents cause myocardial damage by
three basic mechanisms

• Infectious agents cause myocardial damage
• by three basic mechanisms
• invasion of the myocardium
• production of a myocardial toxin, e.g.,
  diphtheria
• immunologically mediated myocardial damage

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Myocarditis

• Myocarditis may be an acute or a chronic process
  and may occur during the peripartum period
• In North America, viruses (especially
  enteroviruses) are presumed to be the most common
  agents producing myocarditis

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• Myocardial involvement may be focal or diffuse
• However, a single small lesion may have profound
  consequences if it is located within the cardiac
  conducting system

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CLINICAL MANIFESTATIONS

• The clinical expression of myocarditis ranges
  from the asymptomatic state secondary to focal
  inflammation to fulminant fatal congestive heart
  failure due to diffuse myocarditis

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• the presence of myocarditis is often inferred
  from ST-segment and T-wave abnormalities on the
  electrocardiogram
• nonspecific symptoms, including fatigue, dyspnea,
  palpitations, and precordial discomfort
• In some cases, the clinical presentation may
  simulate an acute myocardial infarction.

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Electrocardiographic abnormalities

• Abnormalities of the ST segment and T wave
• Atrial and in particular ventricular arrhythmias
• V and intraventricular conduction defects, and,
  rarely, Q waves may be seen
• Complete AV block is usually transient and
  resolves without sequelae, but it is occasionally
  a cause of sudden death in patients with
  myocarditis

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VIRAL MYOCARDITIS

• COXSACKIEVIRUS.
• Both Coxsackie viruses A and B may produce
  myocarditis, although infection with Coxsackie B
  is more common this agent is the most frequent
  cause of viral myocarditis, causing more than
  half the cases.
• Most patients recover completely within weeks

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CYTOMEGALOVIRUS

• Unrecognized infection with cytomegalovirus (CMV)
  is extremely common in childhood, and the
  majority of the adult population have antibodies
  to CMV.
• Primary infection after the age of 35 years is
  uncommon, and generalized infection usually
  occurs only in immunosuppressed patients with
  neoplastic disease, after transplantation, and
  with HIV infection

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Other virus

• DENGUE
• HEPATITIS
• Human Immunodeficiency Virus (HIV)

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RICKETTSIAL MYOCARDITIS

• The rickettsial diseases frequently are
  associated with evidence of myocardial
  involvement, but usually it is subclinical.
  Transient ST-segment and T-wave alterations in
  particular are observed commonly

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RICKETTSIAL MYOCARDITIS

• Q FEVER. Endocarditis is the most common
  cardiac manifestation of infection with R.
  burnettii (Q fever)
• ROCKY MOUNTAIN SPOTTED FEVER. Clinical evidence
  of myocarditis is more common than often
  appreciated in Rocky Mountain spotted fever
  (caused by R. rickettsii)
• SCRUB TYPHUS