Acute Myocarditis

Acute myocarditis refers to acute inflammation of the heart muscles. This can result in sudden weakening of the heart pumping function and/or disturbances in the electrical conduction system of the heart.

Common causes include

• Virus infection affecting the heart
• Autoimmune conditions (e.g systemic lupus erythematosus, rheumatoid arthritis)
• Drug-induced

• Preceding flu-like symptoms (fever, upper respiratory tract symptoms, fatigue, muscle aches)
• Chest pain
• Shortness of breath
• Palpitations
• Unexplained fainting spells

Acute myocarditis is diagnosed by cardiologists, by integrating various clinical information, including

• Patient symptoms
• Clinical examination findings
  • Signs of heart failure
• Laboratory tests
  • Troponin levels: a protein released following heart muscle damage
  • Blood and nasal swab tests, to look for possible viral/ autoimmune causes of acute myocarditis
• Electrocardiogram ('ECG')
  • Electrical tracing of the heart, often indistinguishable from acute myocardial infarction ('heart attack') in acute myocarditis
• Chest radiograph
  • X-ray examination, looking for abnormal heart enlargement/ abnormal fluid collection in the lungs due to acute heart muscle weakening/ heart failure
• Echocardiogram
  • Ultrasound examination which allows doctors to assess heart function
• Cardiovascular magnetic resonance imaging ('Cardiac MRI')
  • Specialised scan looking specifically at the heart muscles, to look for evidence of heart muscle inflammation
• Invasive tests
  • Coronary angiogram: to rule out presence of blood vessel blockages which can account for patient's symptoms
  • Endomyocardial biopsy: sampling of heart muscle, to directly look for presence of inflammation in the heart muscle

Acute management

When a patient is admitted to the hospital with the diagnosis of acute myocarditis, he/ she will be monitored closely for stability, as a proportion of patients will develop severe heart failure due to sudden loss of heart pumping function. Treatment options in this case would include

• Medications to improve heart pumping function ('inotropes')
• Temporary mechanical circulatory support (extracorporeal membrane oxygenation, ECMO)

Chronic management

Most patients with acute myocarditis improve with time. In cases of poor heart pumping function from acute myocarditis, medications will be started to promote heart function recovery.

Patients with acute myocarditis often need repeat cardiac imaging studies to look for signs of heart recovery, as well as looking for evidence of long-term heart muscle damage from the initial inflammation.

The Cardiomyopathy Clinic at the National University Heart Centre, Singapore (NUHCS) provides a comprehensive evaluation and treatment service for patients diagnosed with acute myocarditis.

Heart biopsy sample of a patient with acute myocarditis. Note the numerous inflammatory cells (black arrows) present in the heart muscle tissue, indicating acute, active inflammation of the heart.