Myocarditis

Myocarditis is an inflammation of the heart muscle (myocardium). Myocarditis affects the heart's ability to pump blood and can cause an irregular heartbeat. Many cases may be mild, but sometimes it can be life-threatening.

The most common cause of myocarditis is infection, although there are many other things that can lead to myocarditis including autoimmune diseases, some medicines, illicit drugs and even spider bites and bee stings.

While myocarditis is rare, males are more likely to be affected than females.

Myocarditis can cause mild or severe symptoms. Some people may have no symptoms at all.

Common symptoms may include:

• chest pain or pressure
• fever or flu-like symptoms such as body aches, cough, sore throat, nausea and diarrhoea
• shortness of breath during everyday activities or at rest
• fatigue
• dizziness or light-headedness
• palpitations or rapid heartbeat
• swelling in your legs, ankles or feet

Myocarditis can have many different causes, including:

• viral illnesses, such as influenza, the common cold (adenovirus) and many others
• bacterial, fungal or parasite infections
• autoimmune diseases, for example, lupus or Sjögren's syndrome
• some prescription medicines, such as chemotherapy
• drugs, such as cocaine or amphetamines
• bites and stings, such as scorpion stings, spider bites or bee stings
• vaccines, such as the COVID-19 vaccine — this is rare

Myocarditis can be hard to diagnose because some people have no symptoms while others have a variety of symptoms that can be confused for other health problems.

To help diagnose myocarditis, your doctor will ask about your symptoms, medical and family history, recent infections, vaccinations and what medicines you are taking.

Tests that are used to diagnose myocarditis include:

• blood tests, such as a full blood count (FBC) and troponin
• electrocardiogram (ECG — a test that measures your heart's electrical activity)
• echocardiogram (ultrasound of your heart)
• chest x-ray
• cardiac magnetic resonance imaging (MRI — a scan of your heart using magnetic fields and radio waves)
• heart biopsy (where cells of your heart are sampled for testing in a lab)

The treatment for myocarditis depends on how severe it is and what has caused it. Treatment can range from rest at home and supportive care, to intensive hospital care.

Treatment may include:

• resting and avoiding strenuous exercise for 3 to 6 months
• taking medicines to reduce swelling in the heart
• taking medicines to help with heart rhythm, heart failure or fluid build-up
• treating the cause such as infection
• using a device to support your heart rhythm, such as a pacemaker or defibrillator
• having a procedure, such as cardiac ablation

If your myocarditis is severe, you may need to stay in hospital for intravenous (IV) medicines, support from machines that help the heart pump, or in rare cases, a heart transplant.

Most people recover in a few weeks to months, but recovery time can vary. Ongoing follow-up with a cardiologist (specialist heart doctor) is often needed.

Most people recover fully from myocarditis, but myocarditis can sometimes lead to:

• heart failure
• cardiogenic shock
• arrhythmias
• sudden cardiac death (rare)

There is no specific way to prevent myocarditis, but you can lower your risk. Tips that may help lower your risk of developing myocarditis include:

• keeping vaccinations up to date
• practising good hygiene, such as regular handwashing
• avoiding close contact with people who are unwell
• avoiding illicit drugs
• managing underlying health conditions such as lupus or other autoimmune diseases

• The Heart Foundation provides further information on heart inflammation (Opens in new tab) and heart health information in a range of community languages (Opens in new tab).
• Victor Chang Cardiac Research Institute (Opens in new tab) has a fact sheet on myocarditis (Opens in new tab).
• The Australian Government Department of Health has helpful resources including a video on heart health and heart health checks (Opens in new tab).

Call the healthdirect helpline on 1800 022 222 (known as NURSE-ON-CALL in Victoria). A registered nurse is available 24 hours a day, 7 days a week.

Information for Aboriginal and/or Torres Strait Islander peoples

• Visit Australian Indigenous HealthInfoNet to learn more about cardiovascular health (Opens in new tab).
• The Heart Foundation offers information on how to look after your heart (Opens in new tab) for Aboriginal and/or Torres Strait Islander peoples.