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 features

Symptoms

• Fever
• Chest pain
• Dyspnoea
• Palpitations

Signs

• Soft heart sounds, prominent 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 screen for systemic autoimmune diseases