Myocarditis

Overview

Myocarditis is the acute or chronic inflammation of the myocardium. Continued inflammation and destruction of the myocardium can lead to dilated cardiomyopathy. It is a diagnosis that should be considered in younger patients with chest pain.

Epidemiology

• Seen more in younger people (<50) but can affect all age groups
• Incidence is slightly higher in men

Causes

• Viral infection
  • The most common cause – coxsackievirus, adenovirus, parvovirus B19, enteroviruses, HIV, Epstein-Barr Virus, hepatitis A, and hepatitis C
• Bacterial infection:
  • Diphtheria, syphilis, tuberculosis, Lyme disease, leptospirosis
• Fungal infection
  • Candida species, Aspergillus
• Protozoal infection
  • Chagas’ disease, toxoplasmosis, malaria
• Autoimmune causes:
  • Sarcoidosis, systemic lupus erythematosus, systemic sclerosis, vasculitides, polymyositis
  • Hyperthyroidism
• Drugs:
  • Ethanol, doxorubicin, lithium, cocaine, cyclophosphamide

Presentation

The presentation can vary from asymptomatic with ECG changes to fulminant heart failure, arrhythmias, and cardiac arrest. Common presentations are:

• There is often a history of a viral infection 2-3 weeks prior
• Chest pain
• Dyspnoea
• Orthopnoea
• Syncope
• Fatigue
• Palpitations
• May have soft S1
• May have S3 or S4 gallop

Differential Diagnoses

Pericarditis

• Both present very similarly and it can be difficult to tell them apart
• Symptoms of heart failure suggest myocarditis
• Echocardiography shows left ventricular (LV) dysfunction in myocarditis but not pericarditis

Takotsubo cardiomyopathy

• Both present very similarly and it can be difficult to tell them apart
• There may be a history of an acute emotional or physical stressor within the 2 weeks prior

Acute coronary syndrome

• Patients tend to be older
• Patients tend to have risk factors for atherosclerotic disease

Investigations

All patients

• 12-lead ECG:
  • May show non-specific ST and T-wave changes such as ST elevation and ST depression
• Chest x-ray:
  • Ordered in any patient with shortness of breath
  • May show pulmonary infiltrates if myocardial-induced heart failure develops
• Cardiac troponins:
  • May be elevated
  • To screen for myocardial infarction
• NT-proBNP:
  • May be elevated if myocarditis-induced heart failure develops
• Echocardiogram:
  • Shows global and regional LV motion abnormalities and dilation

Management

All patients

Management involves treating the underlying cause and is supportive if patients have no signs of LV dysfunction. Corticosteroids may be used if there is an underlying autoimmune aetiology.

If LV dysfunction develops, patients are given heart failure treatment.

Complications

• Arrhythmia e.g. atrial fibrillation or ventricular tachyarrhythmia
• Dilated cardiomyopathy
  • Patients should be treated with standard heart failure therapies and referred to a heart failure specialist
• Sudden cardiac death

Prognosis

• The prognosis depends on the patient’s presentation, the LV ejection fraction, and pulmonary artery pressure.