Myocarditis

What is myocarditis?

Myocarditis is the inflammation of the heart muscle. If severe, this inflammation can enlarge and weaken the heart, decreasing the heart’s ability to pump properly. It can also cause irregular heart rhythms (arrhythmia) or a rapid heartbeat. Typically, myocarditis is caused by an infection in the body. The risk of developing myocarditis is rare, but males are more likely to be affected than females.

What are the symptoms of myocarditis?

In the early stages of myocarditis, symptoms are usually mild, but often individuals experience no symptoms at all. Symptoms of myocarditis can vary depending on what caused the disease.

Signs of myocarditis may include:

• Chest pain or pressure
• Shortness of breath even while resting
• Fatigue
• Heart palpitations or rapid heartbeat
• Swelling of the legs and feet due to fluid buildup
• Headache or body aches
• Light headedness
• Fever (common in children)

What are the causes of myocarditis?

Myocarditis occurs when the heart remains stressed and inflamed following an infection. In most cases, myocarditis is caused by a viral infection, such as COVID-19, influenza, the common cold virus (adenovirus), viruses that cause gastroenteritis, HIV and several others. Bacterial infections, parasites, fungi and cancer can also cause myocarditis.

Sometimes myocarditis can occur following a reaction to medication or illegal drugs, or after exposure to a toxic environment.

Myocarditis and the COVID-19 vaccine

UPDATE 23rd September 2022: Please view the latest ‘Guidance on Myocarditis and Pericarditis after COVID-19 vaccines’ from the Australian Government as endorsed by ATAGI and CSANZ.

Heart inflammation or myocarditis has been identified as an extremely rare side effect of the mRNA COVID-19 vaccines. Professor Jason Kovacic is the lead author on a COVID information document published in the journal Vascular Medicine. The document describes that an estimated 12 myocarditis cases have been reported to occur per one million people aged 12 – 39 years following the second dose of an mRNA vaccine against COVID. This is compared to an estimated 450 cases per million who tested positive for COVID-19 (males under the age of 20).

Learn more about these findings and myocarditis and COVID-19 from our cardiologists at the Victor Chang Cardiac Research Institute

How is myocarditis diagnosed?

Diagnosing myocarditis can be challenging because the majority of cases have no symptoms. But early diagnosis is important to try to prevent long-term damage to the heart. The following tests may be conducted to diagnose myocarditis:

• Electrocardiogram
• Chest X-ray
• Echocardiogram
• MRI scan
• Blood tests
• Heart biopsy (to confirm the diagnosis)

How is myocarditis treated?

In mild cases, myocarditis can resolve on its own with rest. Moderate to severe cases of myocarditis require medication and, in some cases, the heart may require temporary support to pump enough blood. Full recovery can take several months, but following treatment many patients can lead a long, full life.

Treatment can include:

• Non-steroidal anti-inflammatory medications (eg. ibuprofen or naproxen)
• Colchicine (another anti-inflammatory medication that is also used to treat gout)
• Corticosteroids (also to reduce inflammation in the body)
• Cardiac medications such as diuretics, beta blockers and ACE inhibitors
• In severe cases treatments such as ventricular assist devices (VAD), intra-aortic balloon pump, ECMO machine or even heart transplant

While myocarditis can reoccur, the risk is low. In rare cases, myocarditis can lead to dilated cardiomyopathy (DCM), the most common cause of heart failure.

Can myocarditis be prevented?

There is no specific prevention for myocarditis, although vaccination against COVID reduces the risk of myocarditis from that cause. Contact your doctor if you have symptoms of myocarditis, particularly shortness of breath or chest pain.