What Is Myocarditis?

Myocarditis, refers to the inflammation of the myocardium, the muscle of the heart. Inflammation weakens the muscle and function of the heart, decreasing efficiency of the heart’s ability to pump blood throughout the body as well as the normal electrical signalling. When this is disrupted, it opens the door for heart issues such as a heart attack, heart failure, or even death. 

Myocarditis is the inflammation of the myocardium, the muscle of the heart. The heart is a muscle that stretches and retracts to pump blood through the body. Inflammation weakens the muscle and function of the heart, decreasing the efficiency of the heart’s ability to pump blood throughout the body as well as the normal electrical signalling of the heart. When the electrical system of the heart is disrupted, other heart issues such as arrhythmias may arise. 

Similar to getting a cut on your skin, if you do not properly allow the skin to heal, your heart can scar. Scar tissue is stiffer than healthy tissue, resulting in the heart putting in more work to pump blood and can lead to more complex heart issues such as dilated cardiomyopathy or heart failure. 

In this article, we will discuss the potential causes, who is at risk, severity, symptoms, and treatment for myocarditis. We will also discuss the correlation between myocarditis and the mRNA COVID-19 vaccine.


Myocarditis is a heart condition referring to the inflammation of the heart muscle. It is predominantly found in young, athletic, assigned males at birth, although anyone can be affected. Causes of the disease are usually due to viral or bacterial infection but can also arise from genetic factors that increase susceptibility to heart problems or autoimmune diseases. This disease is diagnosed through blood tests or imaging. Symptoms may present as shortness of breath, chest pain or discomfort and abnormal heart rhythm. People with mild cases of myocarditis may only need rest and medication for a quick and full recovery. In more severe cases, there may be a need for surgical intervention or prolonged medication, with a chance of recurrence. If you experience any symptoms of myocarditis, consult your doctor.

Causes of myocarditis

While it is not certain what causes one to develop myocarditis, it is suspected that it can be caused by many environmental or genetic factors. Myocarditis most commonly develops from a viral infection such as COVID-19 or flu that triggers the immune system. 

According to the Myocarditis Foundation, myocarditis can develop from any of the following:1,2

  • Viral infection
  • Bacterial infection
  • Fungal infection
  • Cancer
  • Environmental toxins
  • Genetic mutations associated with increased risk of cardiomyopathy
  • Autoimmune disease

Who is at risk of myocarditis?

Myocarditis most often affects young athletic adults, the most high-risk population are people of ages starting during puberty to early 30s, although it can affect anyone.1 People who are assigned male at birth (AMAB) are affected more often as assigned female at birth (ASAB). Athletes are more likely to have myocarditis due to the stress put on the heart during competitions and without proper recovery of the inflamed heart from infection.

Types of myocarditis (Severity)

There are several types of myocarditis, varying in severity; some include:

Acute myocarditis

Acute myocarditis refers to a fast onset of myocarditis, usually developing over a matter of weeks or months. This is usually caused by a viral infection or mRNA vaccine that triggers your immune system. Most patients who are diagnosed with mild acute myocarditis express little to no symptoms and recover with rest and medication.

Fulminant myocarditis

Fulminant myocarditis is a rare sudden and severe onset of myocarditis. This form is often fatal as a result of arrhythmias and organ failure. However, with early detection, treatments can be administered to increase the odds of recovery.3

Chronic myocarditis

Chronic myocarditis refers to repeated symptoms of myocarditis over long periods of time that could be due to an autoimmune response such as Lyme disease. Autoimmune diseases refer to the immune system attacking its own cells, causing repeated inflammation. 

Giant cell myocarditis

Giant cell myocarditis is a rare myocardial disease that is rapidly progressive and frequently fatal. It affects young and middle-aged adults and is associated with an autoimmune disease in 20% of the cases.4 Early indications of GCM include heart failure and arrhythmias but can also be disguised as a heart attack.

Myocarditis and COVID-19 vaccination

While myocarditis and pericarditis have been reported as a side effect of the mRNA COVID-19 vaccine, it is rare. The United States Food and Drug Administration (FDA) and the European Medicines Agency (EMA) reported that the potential risk for either of these conditions is 1 in 10,000 vaccinated people.5 The British Heart Foundation (BHF) reports those who experienced mild symptoms improved with rest and medication.6 

The Center for Disease Control (CDC) still recommended that everyone 6 months and older receive the COVID-19 vaccine unless otherwise advised by a healthcare provider. The known risks of COVID-19 illness outweigh the potential adverse reaction to the mRNA vaccine.

If you have concerns relating to the COVID-19 vaccine, consult with your healthcare provider.

Signs and symptoms of myocarditis

It is important to note that not all patients with myocarditis will present symptoms.

The potential signs and symptoms of myocarditis include:

  • Chest pain or discomfort
  • Shortness of breath
  • Tiredness
  • Abnormal heart rhythm
  • Arrhythmias

If you have any of the above symptoms, please talk with your healthcare provider.

In some cases, myocarditis may feel similar to a heart attack, if this occurs, call emergency services.

How is it diagnosed?

To be diagnosed, your doctor may ask you questions about your medical history. Depending on your history or symptoms, they may send you for tests such as;

Blood test: Blood tests are done to check for proteins that are related to inflammation or heart tissue damage. They can also check antibody levels for infections that are related to myocarditis.

Cardiac MRI (cMRI): An MRI uses magnetic fields and radio waves to produce an image of your heart in real-time. From this, a doctor can determine if the muscle is inflamed based on the shape and structure of your heart.

Chest X-ray: A chest x-ray uses x-ray waves to produce an image of the heart. This can be used to show the size and shape of the heart and lungs.

Endomyocardial biopsy: An endomyocardial biopsy is performed by a cardiologist who feeds a thin, flexible tube through the blood vessel to the heart.  Samples of tissue are taken and evaluated for certain cell types that would indicate heart scarring or damage. Some forms of myocarditis such as giant cell and eosinophilic myocarditis (a type of inflammatory cardiomyopathy characterized by eosinophilic infiltration into myocardial tissue can only be diagnosed through a biopsy).

Management and treatment for myocarditis

Conditions of myocarditis may be mildly acute, presenting symptoms and resolving quickly. Those diagnosed with a mild case may only need rest and medication and are advised against strenuous exercise. If chronic, it may last longer and need longer recovery times and can reoccur from irritants. In severe cases, myocarditis may lead to issues such as a heart attack, heart failure, or death.2

How is myocarditis treated?

There is no one main treatment for myocarditis. A medical professional may advise you of the best course of action to treat symptoms relating to myocarditis; which could include:

  • Treating the cause, if known
  • Treating non-heart related symptoms
  • Treating the symptoms affecting the heart

Those with more severe cases of myocarditis may need prolonged medication or surgery to help heal the heart. 


In mild cases, most patients only need rest and medication. Medications may include:2

  • Painkillers for chest pain
  • Anti-inflammatory drugs
  • Heart medication, such as beta-blockers or angiotensin-converting enzyme (ACE) inhibitors to improve heart function
  • Antibiotics, if related to a bacterial infection

In severe cases, more aggressive treatments may be needed, which may include:

  • Ventricular Assist Device (VAD)
    • A VAD helps pump blood from the lower chamber of your heart (ventricles) to the rest of your body. This is a treatment for patients suffering from weakened heart tissue or in cases of heart failure
  • Heart transplant
    • In the worst cases, the heart is damaged beyond repair. Only 1-8% of patients diagnosed with myocarditis require a heart transplant7 

After a myocarditis diagnosis, it is crucial to take rest and avoid strenuous activity. Your doctor will advise you on the best course of action and time before returning to physical activity.

Tips to improve heart health

To improve overall heart health, your doctor may recommend that you:

  • Avoid tobacco products. Components such as nicotine and tar in tobacco products increase blood pressure and heart rate, increasing the workload on the heart. Smoking has been linked to an increased risk of heart attack and stroke
  • Limit alcohol intake. Drinking too much alcohol regularly has been linked to high blood pressure and increased risk for cardiovascular diseases
  • Limit caffeine consumption. Caffeine products, such as coffee or energy drinks, may cause your heart to beat faster, increasing the workload on your heart

When should I see a doctor?

If you think you may have myocarditis, speak to a doctor. It is important to have regular checkups with your doctor after the diagnosis of myocarditis to check for possible complications.

When can I return to intense physical exercise?

It is important to consult your doctor before returning to intense physical exercise. A study in the Journal of Cardiovascular Translational Research recommends for patients to avoid rigorous physical activity for 3-6 months after myocarditis diagnosis.8 They reported a low risk of cardiac event 1 year after the diagnosis after the resumption of exercise after 3 months for patients diagnosed with acute myocarditis.


Myocarditis is a condition referring to the inflammation of the heart muscle. It is most commonly diagnosed in young, athletic, assigned males at birth. Symptoms such as shortness of breath, irregular heart rhythm, and chest pain may present. In mild cases, doctors may recommend rest from any strenuous physical exercise and medication to treat symptoms. Although listed as a side effect of the mRNA COVID-19 vaccine, it is rare and is still recommended to receive the vaccine. You can help improve your heart health by reducing smoking, alcohol and caffeine consumption. If you have any of the symptoms listed above, consult with your doctor.


  1. Understanding Myocarditis [Internet]. Myocarditis Foundation. [cited 2023 Feb 6]. Available from: https://www.myocarditisfoundation.org/about-myocarditis/
  2. Myocarditis [Internet]. British Heart Foundation. [cited 2023 Feb 6]. Available from: https://www.bhf.org.uk/informationsupport/conditions/myocarditis
  3. Kociol RD, Cooper LT, Fang JC, Moslehi JJ, Pang PS, Sabe MA, et al. Recognition and Initial Management of Fulminant Myocarditis. Circulation [Internet]. 2020 Feb 11 [cited 2023 Feb 7];141(6):e69–92. Available from: https://www.ahajournals.org/doi/10.1161/CIR.0000000000000745
  4. 4. Kandolin R, Lehtonen J, Salmenkivi K, Räisänen-Sokolowski A, Lommi J, Kupari M. Diagnosis, Treatment, and Outcome of Giant-Cell Myocarditis in the Era of Combined Immunosuppression. Circulation: Heart Failure [Internet]. 2013 Jan [cited 2023 Feb 7];6(1):15–22. Available from: https://www.ahajournals.org/doi/10.1161/circheartfailure.112.969261
  5. 5. Kornowski R, Witberg G. Acute myocarditis caused by COVID-19 disease and following COVID-19 vaccination. Open Heart [Internet]. 2022 Mar 1 [cited 2023 Feb 7];9(1):e001957. Available from: https://openheart.bmj.com/content/9/1/e001957
  6. 6. Myocarditis and Covid-19 vaccines: should you be worried? [Internet]. [cited 2023 Feb 7]. Available from: https://www.bhf.org.uk/informationsupport/heart-matters-magazine/news/coronavirus-and-your-health/coronavirus-vaccine-your-questions-answered/myocarditis-and-covid-19-vaccines-should-you-be-worried
  7. 7. CauseInspired. Life After A Heart Transplant [Internet]. Myocarditis Foundation. 2019 [cited 2023 Feb 9]. Available from: https://www.myocarditisfoundation.org/life-after-a-heart-transplant/
  8. 8. Patriki D, Baltensperger N, Berg J, Cooper LT, Kissel CK, Kottwitz J, et al. A Prospective Pilot Study to Identify a Myocarditis Cohort who may Safely Resume Sports Activities 3 Months after Diagnosis. J of Cardiovasc Trans Res [Internet]. 2021 Aug 1 [cited 2023 Feb 9];14(4):670–3. Available from: https://doi.org/10.1007/s12265-020-09983-6
This content is purely informational and isn’t medical guidance. It shouldn’t replace professional medical counsel. Always consult your physician regarding treatment risks and benefits. See our editorial standards for more details.

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Sara Nakanishi

Master’s of Science - Genes, Drugs, and Stem Cells - Novel Therapies, Imperial College London

Bachelor of Science - Biochemistry/Chemistry, University of California San Diego

Hello! My name is Sara and I have a diverse background in science, particularly in biochemistry and therapeutics. I am extremely passionate about heart health and mental illness. My goal is to break down complex scientific topics to share with those with non-scientific backgrounds so they can be well-informed about their conditions and ways to live a balanced life. I believe that education and awareness are key to leading a healthy lifestyle and I hope to inspire others through my writing.

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