Myocarditis

Background

• An inflammatory cardiomyopathy, under subset of 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

• Three 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, N/V; 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

Diagnosis

• ECG: Sinus tach, 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

DDx

• Acute MI
• Pericarditis
• CHF

Treatment

• 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

Dispo

• 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 rateat 5 yrs
  
• Complications
  • Vent. Dysrhythmias
  • LV anneurysm
  • CHF

See Also

Cardiomyopathy

Pericarditis

Source

Rosen's, Tintinalli