Myocarditis

Infective or non-infective myocardial inflammation causing a variable degree of ventricular function, classified by:

Epidemiology and Risk Factors

Incidence of 1-10/100,000, with the highest risk in:

  • 20-40 year olds
  • Males

Pathophysiology

Aetiology

Precipitants may be:

  • Infective
    • Viral
      • Adenovirus
      • Enteroviruses
        • Coxsackievirus
      • Parvovirus B19
      • CMV
      • EBV
      • HSV
      • HIV
      • Influenza
      • COVID-19
    • Bacterial
      • Corynebacterium diptheriae
      • Borrelia burgdorferi
  • Non-infective
    • Autoimmune
    • Sarcoidosis
    • Drugs-induced
      • Chemotherapy
      • Immunotherapy
      • Biological therapies
      • Vaccination
        Generally mild and self-limiting.

Assessment

Presentation may include with:

  • Chest pain
  • Heart failure
    • Cardiogenic shock
      Fulminant myocarditis.
    • New acute heart failure
    • Worsening of chronic heart failure
  • Arrhythmias
    • Typically

History

Key questions if this is the suspected diagnosis. Should also include elements relevant to key differentials.

Examination

Key exam findings if this is the suspected diagnosis. Should also include elements relevant to key differentials.

Investigations

Bedside:

  • Echocardiography

Laboratory:

  • Blood
    • FBE
      • Eosinophil count
    • Troponin
      Most sensitive biomarker.
    • CK
    • BNP
  • Endomyocardial biopsy
    Should be reserved for patients with suspected myocarditis and one of:
    • Cardiogenic shock
    • Mobitz II or greater AV block, without significant LV dilatation
    • Ventricular arrhythmias, without significant LV dilatation
    • Eosinophilia
    • Systemic inflammatory disease
    • Cardiac dysfunction with immune checkpoint inhibitor therapy

Imaging:

  • Angiography
  • Cardiac MRI
    • Highest sensitivity at 2-3 week mark
    • Features may include:
      • Early gadolinium enhancement suggestive of hyperaemia
      • ↑ T2 signal suggesting oedema
      • Late gadolinium enhancement suggesting necrosis or fibrosis
        Poor prognostic sign.

Other:

Diagnostic Approach and DDx

Management

  • Manage cardiac failure
    Anti-failure therapy if haemodynamically stable, otherwise consider inotropic and mechanical support.
  • Manage arrhythmias
  • Consider immunosuppression
  • Prevent further myocardial injury
    • Biventricular unloading
    • Maintain coronary perfusion
  • Consider durable mechanical support or transplant

Heart failure management is covered under Management.

Resuscitation:

  • C
    • Arrhythmia
      • Pacing

Specific therapy:

  • Pharmacological
    • Immunosuppression
      • Indicated for eosinophilic myocarditis, giant-cell myocarditis, cardiac sarcoidosis, or underlying autoimmune disease
      • Limited evidence
      • Regimens include:
        • Prednisone
        • Azathioprine
  • Procedural
    • Durable mechanical support or transplant
      Should be considered if temporary mechanical support is still required after 14-21 days.
    • Permanent PPM/ICD
      Should be deferred 3-6 months following acute event.
  • Physical

No specific therapies are available for lymphocytic myocarditis.

Supportive care:

Disposition:

  • Limit physical activity in 3-6 months following acute illness

Preventative:

Marginal and Ineffective Therapies

Anaesthetic Considerations

Complications

Prognosis

↑ Risk of death or transplantation with:

  • Poorer LVEF
  • Cardiogenic shock
  • ↑ Degree of AV nodal blockade
  • Ventricular arrhythmias

Key Studies

References

  1. Basso C. Myocarditis. New England Journal of Medicine. 2022 Oct 20;387(16):1488–500.