Myocarditis

Refers to an inflammatory process leading to acute, subacute or chronic injury of the myocardium

Aetiology

  • Viral infection is the most common cause of acute myocarditis
    • Coxsackievirus is the most common viral cause in Europe and the USA; however, most viruses are potential agents, including adenovirus, influenza A and B, HIV, EBV, hep B and C, borrelia burgdoferi (Lyme disease)
    • Global causes include Chaga’s disease due to trypanosomiasis (South America), and diptheria (most common cause worldwide)
  • Immune-mediated hypersensitivity reactions can also cause myocarditis
    • Hypersensitivity to infection - rheumatic fever after strep sore throat
    • Hypersensitivity to drugs - eosinophilic myocarditis
    • Systemic autoimmune diseases e.g. SLE

Clinical presentation

Symptoms

  • Fever
  • Chest pain
  • Dyspnoea
  • Palpitations

Signs

  • Soft heart sounds, prominant third sound
  • Tachycardia
  • Cardiac failure

Investigations

  • ECG - changes may include ST-segment elevation/depression, T-wave inversion, atrial arrhythmias, transient AV block
  • Bloods - raised troponin and creatinine kinase, raised inflammatory markers
  • CXR - enlarged heart and/or signs of heart failure
  • Viral PCR may be used - throat swab and stool for enteroviruses, throat swab for influenza
  • Consider autoantibodies to scren for systemic autoimmune diseases
  • Endomyocardial biopsy is the definative test but very risky so only done if it is thought this will change the management plan
  • Cardiac MRI can be used to differentiate between acute myocarditis and infarction

Management

  • Treatment is mainly supportive
  • Treat the underlying cause if possible