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ESSENTIALS OF DIAGNOSIS

  • Often follows an upper respiratory infection.

  • May present with chest pain (pleuritic or nonspecific) or signs of heart failure.

  • Echocardiogram documents cardiomegaly and contractile dysfunction.

  • Myocardial biopsy, though not sensitive, may reveal a characteristic inflammatory pattern. MRI has a role in diagnosis.

GENERAL CONSIDERATIONS

Cardiac dysfunction due to primary myocarditis is presumedly caused by either an acute viral infection or a postviral immune response. Secondary myocarditis is the result of inflammation caused by nonviral pathogens, medications, chemicals, physical agents, or inflammatory diseases (such as systemic lupus erythematosus). The list of both infectious and noninfectious causes of myocarditis is extensive (Table 10–15).

Table 10–15.Causes of myocarditis.

While poorly understood, much effort has been made to decipher the pathophysiology of infectious myocarditis. A direct virus-related cytolysis of myocytes appears to precede inflammatory infiltration in many instances. Endothelial cell infection creates endothelial dysfunction. When the contractile cells or interstitial cells and matrix become involved, ventricular dilation and systolic heart failure often ensues. Involvement of vascular tissue can indirectly affect myocardial function, possibly by creation of chronic ischemia. Direct cytopathic apoptosis, activation of the innate immune system, and cardiac ...

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