Myocarditis (Heart Muscle Inflammation)

Myocarditis, or inflammation of the heart muscle, is a condition in which the heart muscle becomes inflamed. The inflammation can weaken the heart’s pumping ability and cause arrhythmias or heart failure. Symptoms range from mild fatigue to severe cardiac symptoms.

The condition is most common in young adults and may be associated with a viral infection, such as the flu. Most people recover fully, but some require longer follow‑up and treatment.

What causes myocarditis?

The most common cause of myocarditis is a viral infection, such as influenza or enterovirus. Less common causes include:

  • Bacterial or fungal infections
  • Autoimmune diseases (e.g., rheumatic diseases)
  • Certain medications or substances
  • COVID‑19 virus

The inflammation may begin without symptoms after an ordinary infection and develop gradually.

Symptoms of myocarditis

The symptoms of myocarditis can be vague and resemble those of other heart conditions. Typical symptoms include:

  • Unusual fatigue and exhaustion
  • Shortness of breath during exertion or at rest
  • Chest pain, especially at rest
  • Heart palpitations, fluttering sensations, or arrhythmias
  • Poor exercise tolerance
  • Fever or flu‑like symptoms

Symptoms may appear several days or weeks after an infection. In some people, the disease progresses rapidly, while in others the symptoms remain mild.

Diagnosing myocarditis

Myocarditis is diagnosed based on symptoms, an electrocardiogram (ECG), blood tests, and imaging studies. Diagnosis may require:

  • Electrocardiogram (ECG)
  • Cardiac biomarkers (e.g., troponin)
  • Echocardiography
  • Cardiac MRI

In some cases, a heart muscle biopsy is performed.

Treatment and recovery

Most cases of myocarditis resolve on their own. Treatment depends on the severity of symptoms and the heart’s functional capacity:

  • Rest and recovery from the infection are the most important treatments
  • Anti‑inflammatory medications are used when needed
  • In more severe cases, treatment for heart failure is initiated
  • Arrhythmias are treated according to symptoms

Physical activity must usually be avoided for 3–6 months after the inflammation. Returning to sports too early can worsen the condition.

Recovery and follow‑up

Most patients recover completely. Recovery time varies from a few weeks to several months. Heart function is monitored regularly during recovery:

  • Echocardiography
  • ECG follow‑ups
  • Exercise testing before resuming physical activity

Some patients require long‑term follow‑up if permanent changes remain in the heart.

When to see a doctor

Contact a doctor if you experience:

  • Unusual fatigue or shortness of breath after a flu‑like illness
  • Chest pain, especially at rest
  • Heart palpitations or fluttering sensations
  • Poor exercise tolerance during normal physical activity

Myocarditis can develop unnoticed, so symptoms should not be ignored.

The heart is sensitive to inflammation — if symptoms are concerning, seek evaluation.