What is myocarditis?

Myocarditis is an inflammation of the heart muscle, that leads to a reduction in the heart's pumping function. The most common cause is a viral infection. Other possible causes are a bacterial infection, parasites, medications, drugs or after radiation therapy. This may cause mild or unspecific symptoms, such as fever, joint pain, chest pain, shortness of breath and a rapid pulse. In some cases, myocarditis improves without specific treatment. In other cases, the underlying cause may require targeted treatment and the heart may need medications to support its function while it recovers. In many cases, the symptoms of myocarditis will get better within days to weeks. Severe episodes of myocarditis are uncommon, but can cause heart muscle damage, which may be life-threatening.


Myocarditis is inflammation in the heart muscle. Inflammation causes the muscle to swell and become weak, which affects the heart's ability to pump blood effectively. There are multiple causes of myocarditis including viral, bacterial or parasite infections, drugs (including alcohol), certain medications, radiation therapy of the chest, and an overactive immune system. A viral infection is the most common cause. Myocarditis is thought to be not very common, but it is difficult to know exactly how common it is, and many people have no or only mild symptoms. Although the condition can affect people of all ages, it tends to be most common in people aged between 20 and 50. In people with HIV infection myocarditis is also more likely.


People with myocarditis may have chest pain, palpitations, joint pain, fatigue, fainting or fever. If the inflammation of the heart muscle leads to a reduction in the pumping function, symptoms of heart failure may also occur, such as swelling of the legs and shortness of breath.


The diagnosis is based on the symptoms and a physical examination. An electrocardiogram (ECG or heart trace) is often done to investigate for signs of damaged heart muscle and heart rhythm problems. An ultrasound of the heart (an echocardiogram) is done to investigate the movement of the heart. In some cases a small sample of the heart muscle is taken (a biopsy) and investigated to confirm the diagnosis.


The treatment of myocarditis depends on the severity of symptoms. People who have been diagnosed with this condition should rest and avoid vigorous activities. A doctor can advise about when certain activities can be resumed. If the myocarditis only causes mild symptoms, no other treatment may be needed. The underlying cause should be treated if possible. Medications might be needed to support the heart and blood pressure until the heart muscle recovers. This might include medications to improve the heart function, to reduce blood pressure and to remove excess fluids from the body.


Taking steps to prevent the spread of viral infections, such as staying home when sick and washing hands regularly, may help to prevent some episodes of myocarditis.

Other names for myocarditis

  • Heart muscle inflammation