Myocarditis refers to inflammation of your heart muscle. It’s often caused by a bacterial or viral infection.

Myocarditis is a disease where the heart muscle, known as the myocardium, becomes inflamed. This muscle contracts and relaxes to pump blood in and out of the heart and to the rest of the body.

When the myocardium becomes inflamed, its ability to pump blood becomes less effective. This causes problems like an abnormal heartbeat, chest pain, and trouble breathing.

In extreme cases, it can cause blood clots leading to a heart attack or stroke, damage to the heart, or death.

Normally, inflammation is your body’s response to a wound or infection. For example, when you cut your finger, the tissue around the cut quickly swells up and turns red. These are classic signs of inflammation, during which the cells of your immune system rush to the site to begin repairs.

But sometimes the immune system or another cause of inflammation leads to myocarditis.

Keep reading to learn more about myocarditis, what can cause it, and how it’s diagnosed and treated.

Many times, the exact cause of myocarditis isn’t known. In fact, it’s estimated that the cause of an acute case of myocarditis is unknown 50 percent of the time. This is called idiopathic myocarditis.

When the cause of myocarditis is known, it’s usually due to an infection. In some cases, the organism or pathogen that causes disease can find its way to the heart and directly damage the heart muscle. In other cases, the immune system responds to the infection, resulting in an inflammatory response that can affect the heart muscle.

Additionally, some autoimmune diseases, like lupus, can cause the immune system to mistakenly turn against the heart, resulting in inflammation and myocardial damage.


Viruses are the most common cause of myocarditis. Some examples of viruses that are known to cause myocarditis include:

  • coxsackievirus group B, a type of enterovirus
  • parvovirus B19, which is the cause of fifth disease
  • adenovirus, a type of virus that causes the common cold
  • SARS-CoV-2, the coronavirus that causes COVID-19

Other possibilities include:

  • echoviruses, which are known to cause gastrointestinal infections
  • hepatitis C virus, a viral cause of liver inflammation (hepatitis)
  • Epstein-Barr virus, the cause of infectious mononucleosis
  • herpes simplex virus, which can cause oral or genital herpes
  • rubella virus, which causes German measles
  • human immunodeficiency virus (HIV), a virus that attacks cells of the immune system


Myocarditis can also result from a bacterial infection. A few examples of bacteria that can cause myocarditis are:


Fungi are rarer causes of myocarditis. In general, serious fungal infections are more common in people who have a weakened immune system.

If myocarditis is caused by a fungal infection, it’s typically caused by Candida or Aspergillus species. Candida is typically associated with vaginal yeast infections and an oral infection called thrush. Aspergillus is a mold that can cause lung infections in immunocompromised individuals.


Parasites are microorganisms that live off other organisms to survive. They can also cause myocarditis. This is rare in the United States. It’s more commonly seen in Central and South America, where the parasite Trypanosoma cruzi causes a condition known as Chagas disease.

Autoimmune disease

Autoimmune diseases that cause inflammation in other parts of the body can also cause myocarditis. Some examples include lupus and rheumatoid arthritis.

Giant cell myocarditis

In very rare cases, myocarditis may be caused by a condition known as giant cell myocarditis (GCM) that involves the growth of abnormally large cells that cause inflammation and damage to the heart muscle. GCM is a serious condition that progresses rapidly and is more common in young to middle-aged adults.

Individuals with GCM often develop symptoms such as:

  • swollen ankles
  • an abnormal heartbeat
  • chest pain
  • shortness of breath
  • weakness or fatigue

While COVID-19 is often associated with respiratory illness, we now know that it can impact many other parts of the body. This includes the heart, where it can cause myocarditis.

The way that COVID-19 causes myocarditis is unknown, although doctors and scientists do have some theories, which include one or a combination of the following:

  • the virus could be directly infecting the heart muscle, which contains receptors for the virus
  • the activity of the immune system as it tries to respond to COVID-19 could be leading to myocarditis
  • hypoxia, a reduction in the oxygen levels in your body’s organs and tissues, could be contributing to myocarditis

A 2021 study by a group at the Centers for Disease Control and Prevention (CDC) analyzed data from a large healthcare database between March 2020 and January 2021. The study included data from over 36 million people. The researchers found that:

  • Out of those who had myocarditis, 41.7 percent had a history of COVID-19. Most of those in that group (89.6 percent) received both of their diagnoses in the same month.
  • The incidence of myocarditis in the study population was:
    • 150 per 100,000 people with COVID-19
    • 9 per 100,000 people without COVID-19
  • Overall, people with COVID-19 have almost 16 times the risk of developing myocarditis, compared to those without COVID-19.

A 2021 systematic review included 59 studies reporting myocarditis during COVID-19 hospitalization. It found that certain other preexisting health conditions were common in people with myocarditis and COVID-19. These included:

Myocarditis and COVID-19 vaccines

Myocarditis is also a rare side effect of the COVID-19 vaccine. According to the CDC, this side effect is more common:

  • in male patients, particularly those who are adolescents or young adults
  • following vaccination with an mRNA vaccine, which includes the Pfizer-BioNTech and Moderna vaccines
  • after receiving the second dose of an mRNA vaccine
  • within a week of getting vaccinated

A 2021 cohort study estimated that, overall, myocarditis only impacts 1.7 per 100,000 people within 28 days of receiving an mRNA-based COVID-19 vaccine.

Another 2021 study examined 139 adolescents and young adults with suspected myocarditis after their COVID-19 vaccine. Researchers observed that most participants experienced a mild course of illness that responded quickly to treatment.

This aligns with another 2021 study of 2.5 million individuals who’d received the Pfizer-BioNTech vaccine. In this group, 54 cases of myocarditis were reported. The highest incidence was among male participants between 16 and 29 years old. In most cases, myocarditis was mild or moderate in severity.

You’re still at a higher risk of myocarditis from COVID-19 than you are from the COVID-19 vaccines.

A 2021 study estimated 40 myocarditis events per 1 million people in the 28 days after testing positive for COVID-19. This is compared to an estimated 10 myocarditis events per 1 million people in the 28 days after the second dose of the Moderna vaccine.

It’s possible for myocarditis to develop without displaying any symptoms. If symptoms do develop, they often include:

Because myocarditis is often caused by a viral infection, you may also experience flu-like symptoms prior to the onset of myocarditis symptoms. This can include symptoms such as:

To diagnose myocarditis, your doctor will first take your medical history. They’ll ask:

  • questions about your symptoms
  • whether you’ve had an infection recently
  • if you’ve been previously diagnosed with myocarditis

They’ll then perform a physical examination. They’ll listen to your heart and lungs and may check your legs and feet for any signs of swelling.

Though myocarditis can sometimes be difficult to diagnose, your doctor can also use several tests to narrow down the source of your symptoms. These tests include:

  • Blood tests. Blood tests use a sample of blood from a vein in your arm to check for signs of infection or inflammation. Examples of blood tests that may be ordered include:
    • tests for autoantibodies, which are antibodies that may be targeting your heart muscle and may be present with autoimmune disease
    • a B-type natriuretic peptide (BNP) blood test that detects a rise in the levels of the BNP hormone, which indicates heart failure
  • Electrocardiogram (ECG). An ECG measures the electrical activity in your heart and can be used to detect abnormal heart rates and rhythms that may indicate damaged heart muscle.
  • Echocardiogram. An echocardiogram creates an ultrasound image of the heart and can help detect structural or functional issues in the heart and adjacent blood vessels.
  • Chest X-ray. A chest X-ray can show chest anatomy and potential signs of heart failure.
  • Heart CT scan: A heart CT scan uses multiple X-ray images to create a cross-sectional, detailed image of your heart.
  • Heart MRI. A heart MRI can detect signs of inflammation in your heart muscle; it can also allow your doctor to evaluate your heart’s size and shape.
  • Myocardial biopsy. With a myocardial biopsy, a small sample of heart muscle tissue is collected during a heart catheterization. This allows your doctor to examine the sample for signs of myocarditis.

The treatment of myocarditis depends on the source and severity of the myocardial inflammation. In many cases, myocarditis improves with proper measures, and you’ll recover completely.

Some potential treatment options for myocarditis include:

  • Corticosteroids. Corticosteroids are medications that lessen the intensity of, or dampen, your immune response and help to lower inflammation levels.
  • Cardiac medications. If you have myocarditis and signs of heart failure, your doctor may prescribe a cardiac medication to reduce the amount of work your heart is doing. Beta-blockers, ACE inhibitors, ARBs, and cardiac inotropes are examples of these medications.
  • Diuretics. Therapy with diuretics can help reduce the accumulation of fluid.
  • Ventricular assist devices (VAD). If myocarditis is more severe or if your heart needs help while it’s recovering, a VAD may be used to help pump blood from the lower chambers of your heart to the rest of your body.
  • Treating other conditions. If myocarditis is due to a medical condition like an infection or an autoimmune disease, your doctor will also take steps to treat that as well.

These treatments can help ease the heart’s workload so it can heal itself. While you recover, your doctor may also recommend:

  • getting plenty of rest
  • limiting your fluid intake
  • reducing the amount of salt in your diet

Additionally, engaging in high levels of physical activity can increase the risk of sudden cardiac death (SCD) during your recovery period. Because of this, you may want to avoid rigorous physical activity for at least 3 to 6 months after your diagnosis.

If your myocarditis is severe and your heart is failing, other more invasive procedures may be performed in the hospital. Implantation of a pacemaker or a defibrillator may be necessary. When the heart is extremely damaged, doctors may recommend a heart transplant.

Myocarditis can be either acute or chronic. Acute refers to a condition that comes on suddenly. Chronic conditions are those that are persistent or long lasting.

Acute myocarditis is typically what we think of when we talk about myocarditis. Usually, a short amount of time passes, often less than a month, between when your symptoms come on and when you receive a diagnosis. Most cases of acute myocarditis resolve after you receive treatment.

Generally speaking, chronic myocarditis is when your symptoms linger or are more difficult to treat. This appears to have something to do with the immune response. In fact, it’s often associated with autoimmune diseases, which can cause increases in inflammation in the body.

It’s possible for myocarditis to cause significant damage to the heart. Because of this, a variety of complications can result, such as:

  • arrhythmia, a condition in which your heartbeat can be too fast, too slow, or irregular
  • cardiomyopathy, a condition in which your heart muscle weakens and cannot pump blood effectively
  • heart failure, where your heart has a hard time pumping enough blood to the organs and tissues of your body
  • heart attack, in which the blood supply to a part of your heart is cut off, causing heart tissue to die

Myocarditis is also linked to sudden cardiac death (SCD). This is when the heart suddenly and unexpectedly loses function and stops beating.

SCD predominantly affects young adults. One 2019 study found that 6 percent of SCD deaths were due to myocarditis.

The exact incidence of myocarditis in children and adolescents is unknown, although some estimates have put it at 0.15 to 0.6 percent in the overall population. While the condition can occur within this population at any age, most cases happen in infants and teenagers.

Myocarditis in children shares many of the characteristics of myocarditis in adults. However, most cases of myocarditis in children are acute rather than chronic. According to the American Heart Association, the most common symptoms reported in children are:

Myocarditis can be difficult to diagnose in children. This is because symptoms can be nonspecific and can be mistaken for those of more common conditions like asthma or pneumonia. Additionally, performing a myocardial biopsy, the gold standard for myocarditis diagnosis, carries more risk in children.

Myocarditis in children must be carefully managed. While many children recover spontaneously, some can progress quickly to more severe symptoms that put them at a higher chance of experiencing heart damage. When this occurs at a young age, it can have a significant effect on lifelong health.

In addition to myocarditis, there are two other types of heart inflammation. These are endocarditis and pericarditis.

Like myocarditis, both conditions are often caused by infections. However, they affect different parts of the heart.

About endocarditis

Endocarditis is the inflammation of the tissue that lines the inside of your heart, which is called the endocardium.

It’s typically caused by a bacterial infection that reaches the heart through the bloodstream. It tends to affect the heart valves more often than the chambers of the heart.

Endocarditis can be life threatening. This is because clumps of germs on the endocardium can break off and interrupt blood flow, leading to a heart attack or stroke. Additionally, the infection may cause damage to the heart or spread to other parts of the body.

About pericarditis

Pericarditis is an inflammation of the protective sac that surrounds your heart, which is called the pericardium.

In addition to an infection, it can also happen due to:

  • autoimmune diseases
  • a previous injury
  • surgery of your chest or heart

Many instances of pericarditis resolve with treatment, although it can take a long time to make a complete recovery. In some cases, complications like scarring of the pericardium or fluid accumulation around the pericardium can occur.

It’s not possible to completely prevent myocarditis. However, taking steps to avoid infections can help lower your risk of developing myocarditis. Steps you can take include:

The outlook for myocarditis diagnosis is generally positive. Many people with myocarditis will recover without any long-term negative effects on their heart.

It’s important to be patient with your recovery process. In some cases, it can take a long time to fully recover from a bout of myocarditis — up to 3 to 7 years.

During your recovery period, your doctor will continue to monitor you to determine if your treatment was effective and if there are any adverse effects on your heart.

In some cases, myocarditis can damage the heart and cause arrhythmia, heart failure, or cardiomyopathy. These conditions typically require some form of ongoing management.

It’s possible for acute myocarditis to recur. One 2014 study found that over a 4.5-year follow-up period, the recurrence rate of myocarditis was 10.3 percent.

Many people with myocarditis go on to recover completely. However, the condition can also cause permanent damage to the heart muscle. This can lead to complications like arrhythmia and heart failure.

It’s important to seek prompt medical attention if you experience unexplained symptoms like chest pain or shortness of breath. A doctor can evaluate your symptoms to determine if they’re due to myocarditis or another condition.