Myocarditis is an inflammation of the heart muscle. There are various causes but it is usually caused by a virus. The symptoms and possible problems can range from no symptoms at all, to life-threatening heart failure depending on the severity of the infection. Many people with myocarditis recover completely. However, it can cause serious problems and even death in some cases.

What Causes Myocarditis And Whom Does It Affect?

Myocarditis means inflammation of the myocardium. The myocardium is the heart muscle. Myocarditis can affect anyone and occur at any age. There are various causes; many are mild and some are serious.

Causes include the following:

  1. Viral infection
    Many types of viral infection can affect any part of the body, including the heart muscle. Myocarditis may develop at the same time as, or more often just after, a viral throat or chest infection. The body’s immune system can clear many types of virus. This means that many cases of viral myocarditis go away on their own within a week or so.
    Sometimes the inflammation in the heart lasts longer than other features of the infection. The virus may have gone but the immune system may over-react. If this happens it will cause inflammation which persists for a time in the heart.
  2. Unknown Cause (idiopathic myocarditis)
    In many people with myocarditis, the cause is not found. However, for the majority of these people it is likely to be caused by a virus that could not be confirmed by a test.
  3. Other Causes
    Other causes of myocarditis are much less common. They include:

    1. Chagas’ disease.
    2. Lyme disease.
    3. Giant cell myocarditis.
    4. A rare side-effect of some medicines and a rare complication of various diseases.
    5. Other damaging agents. For example, inflammation in the heart can be caused by excess alcohol, radiation, certain chemicals and certain poisons.
    6. Rejection following a heart transplant.

What Are The Symptoms Of Myocarditis?

The symptoms depend on the cause and severity of the inflammation. Many people with viral myocarditis do not have any heart-related symptoms. The heart inflammation may be suspected by some changes on a heart trace (electrocardiogram, or ECG). If symptoms do develop they can include:

  • Chest pain
  • Fever (raised temperature)
  • A fast heartbeat – faster than usual for a normal high temperature (fever)
  • An irregular heartbeat
  • Tiredness
  • Shortness of breath

What Are The Possible Complications?

Possible complications include:

  • Sudden loss of consciousness (syncope).
  • Abnormally fast, slow or irregular heartbeat (cardiac arrhythmias).
  • Heart failure which can cause shortness of breath, swelling of the legs and tiredness.

How Is Myocarditis Diagnosed?

The symptoms are likely to lead to the possible diagnosis of myocarditis.

A heart trace of the electrical activity of the heart (electrocardiogram, or ECG) may be done.

A chest X-ray may show the heart is larger than normal. Blood tests can be done to test for some of the viruses that can cause myocarditis. An ultrasound scan or cardiac MRI (Magnetic resonance imaging)  scan may show how your heart is being affected.

Some people need to have an endomyocardial biopsy. This involves taking a very small tissue sample of the heart to investigate for the cause of myocarditis. Newer tests which are more sensitive at diagnosing some of the viruses are currently being developed.

What Is The Treatment Of Myocarditis?

The treatment of myocarditis will depend on the cause and severity of myocarditis. Bed rest is usually recommended at the onset of myocarditis. Athletic activities should be avoided for six months. This aims to avoid putting undue strain on the heart muscle. Pain killers will help to ease chest pain and high temperature (fever).
There is no treatment that will cure a viral infection. For most people with viral myocarditis, the virus clears away on its own without any treatment, often within a week or so.
In the past, the use of medicines called steroids has been tried. However, there are no clinical studies which demonstrate steroids as being beneficial other than for giant cell myocarditis.
Different treatments for myocarditis are currently being investigated in other clinical studies.
For the more uncommon causes, or if complications develop, a range of treatments may be needed.

For example:

  • Medication to treat heart failure or irregular heartbeat.
  • A pacemaker if certain irregular heart rhythm develop.
  • Antibiotic medicines if the cause of the myocarditis is a germ (a bacterial infection).
  • Steroid medication if the cause is giant cell myocarditis.
  • Stopping alcohol if alcohol is the cause.

What Is The Outlook (Prognosis)?

In most cases of viral myocarditis, the illness goes away on its own and there are no complications. Symptoms may last only a few days or weeks. However, some types of viral infection are more serious and can cause more severe or persistent inflammation and complications.

Complications are more likely with the more uncommon causes of myocarditis. Sometimes the inflammation clears but the heart is left with some permanent damage like heart failure which may require long-term medication.In some cases, the inflammation and heart damage are so severe that the only treatment option is a heart transplant.

Myocarditis is fatal in some cases. In some cases the infection gets worse and becomes unresponsive to treatment. Death can occur some time after the diagnosis is made. Also, some cases of sudden death in a previously healthy person are due to an acute myocarditis that develops rapidly.

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Last reviewed : 16 January 2015
Writer/Translator : Dr. Ainol Shareha bt. Sahar
Accreditor : Dato’ Dr. Abdul Hadi b. Jaafar