Myocarditis

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Background

  • Inflammatory cardiomyopathy (dilated cardiomyopathy) caused by necrosis of myocytes from infectious agents, their toxins, and cytotoxic effects of activated host immunity
  • Majority caused by enterovirus (Cocksackie B) and adenovirus. Also influenza A/B, Hep B, B Hemolytic Streptococcus, Mycoplasma, Mumps, CMV and Toxoplasma (cardiac transplant), Chagas (leading cause worldwide) Trichinosis, Diphtheria, Lyme
  • Drugs: Doxorubicin, Cocaine

Phases

  • Acute: Viral cytotoxicity and focal necrosis
  • Subacute: Host's humoral/immune response leading to further cell injury
  • Chronic: Diffuse myocardial fibrosis and cardiac dysfunction

Clinical Features

  • Typically young/few risk factors for CAD
  • Chest pain
  • No sensitive symptom or sign but can have flu like syndrome: fever, fatigue, myalgia, nausea and vomiting; tachycardia (out of proportion to fever), tachypnea, new onset CHF
  • In Peds: grunting, retractions, ronchi. Infants may have fulminant syndrome: Fever, cyanosis, respiratory distress, tachycardia, cardiac failure, ventricular dysrhythmias
  • May have pericardial friction rub
  • Consider this diagnosis in the septic-appearing patient who gets WORSE after receiving IV fluids.

Differential Diagnosis

Evaluation

  • ECG: Sinus tachycardia, low voltages, prolonged QTc, AV block, Acute MI pattern (Usually >1 vessel distribution)
  • TropI: Elevated
  • Echo: Decreased LVEF, global hypokinesis, regional wall motion abnormalities
  • Contrast MR
  • Nuclear Study: Widespread uptake indicating myocyte necrosis
  • Viral titers
  • Endocardial biopsy: Gold standard

Management

  • Acute Phase: Antiviral agents may be effective with replicating virus: Pleconaril/Ribavirin
  • Subacute: Studies have not shown efficacy of immunosupressants. Peds: High dose IVIG
  • Chronic: Treat CHF symptoms, Ventricular Assist Devices (VAD), cardiac transplant

Disposition

  • If CHF: Admit to monitored bed; ICU for hemodynamic instability
  • Fulminant myocarditis has best prognosis
  • Mortality: 20% 1 yr/ 50% 5 yr
  • Children with 70% survival rate at 5 yrs

Complications

  • Ventricular dysrhythmias
  • LV anneurysm
  • CHF

See Also

References