Myocarditis occurs when a muscle in the heart called the myocardium becomes inflamed. This inflammation can affect the electrical system of the heart and reduce the heart’s ability to pump blood around the body.

The myocardium is the muscular center layer of the heart. It sits between the outer layer muscle, or epicardium, and the inner layer muscle, or endocardium.

In severe cases, myocarditis can cause blood clots to form because the heart is not pumping out blood properly. This could lead to serious conditions, such as heart attack or stroke.

This article will list the potential causes of myocarditis before exploring possible symptoms. It will then explain how doctors might diagnose and treat myocarditis and explore some possible complications that could arise from the condition.

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According to the National Organization for Rare Disorders, most cases of myocarditis have no known cause.

However, some possible causes of myocarditis include:

Viral infections

When doctors can find a cause for myocarditis, the cause is usually a viral infection.

In these cases, the virus causes inflammation. This can mean that the heart is strained even when the infection has cleared up.

Viral infections that can cause myocarditis include:

Bacterial infections

Several types of bacterial infection can cause myocarditis. These include:

Endocarditis

Sometimes, myocarditis manifests as a complication of endocarditis.

Endocarditis is an infection of the heart valves, heart muscle, or inner lining of the heart chambers.

Diphtheria

The bacterium Corynebacterium diphtheriae, which causes diphtheria, can also cause myocarditis.

This bacterium produces a toxin that can stretch out the heart muscle and cause inflammation.

Lyme disease

Myocarditis can also happen due to Lyme disease.

Lyme disease is an infection that can occur following a bite from a tick that carries the bacterium Borrelia burgdorferi.

Chagas disease

Chagas disease can cause myocarditis by infecting the heart muscle. A person can experience Chagas disease if they have come into contact with a parasite called Trypanosoma cruzi.

According to the Centers for Disease Control and Prevention (CDC), this parasite lives in the Americas, especially in more rural parts of Latin America.

Autoimmune conditions

According to the National Center for Advancing Translational Diseases, autoimmune conditions occur when the body’s immune system begins to attack healthy tissue.

Some autoimmune conditions that could give rise to myocarditis include:

Lupus

According to the Lupus Foundation of America, lupus can cause the myocardium to become inflamed.

Often, inflammation of the myocardium happens when there is also inflammation in other parts of the body.

Even if myocarditis has other causes, a person with lupus can still be at higher risk of developing complications from myocarditis. This is because lupus can put a person at higher risk of infection.

Moreover, people with lupus sometimes need to take immunosuppressant medications, which can increase their risks.

Rheumatoid arthritis

In rare cases, rheumatoid arthritis can also cause myocarditis.

One 2020 study lists myocarditis as a main heart-related complication of rheumatoid arthritis.

It goes on to explain that cardiac MRIs can help diagnose myocarditis as a complication of rheumatoid arthritis. Doctors can help treat it by having the person stop any immunosuppressant treatments.

Environmental toxins

Several environmental factors may cause myocarditis. These include:

Heavy metals

According to one 2020 article, exposure to some heavy metals can cause myocarditis. These include:

  • copper
  • iron
  • lead

Venom

In rare cases, myocarditis may occur following a spider or snake bite. In these cases, it happens as a toxic effect of the venom.

Myocarditis can affect anyone at any age. Some people do not experience symptoms.

However, people who do experience symptoms may notice the following:

Early diagnosis of myocarditis is key to preventing long-term heart damage. It can be difficult to diagnose, but a doctor can use several tests to narrow down the source of the symptoms.

According to the Myocarditis Foundation, these tests can include:

  • Electrocardiogram: This test looks at the heart’s electrical patterns to see if there are any unusual rhythms that might indicate a damaged heart muscle.
  • Chest X-ray: This test can show the shape and size of the heart and any fluid around the heart that could indicate heart failure.
  • Echocardiogram: Sound waves help create moving images of the beating heart. It can show whether or not the heart has become bigger and whether or not it has problems pumping blood.
  • Biopsy: Doctors may choose to remove a sample of heart muscle tissue for analysis to check for inflammation or infection.
  • MRI: This test can show signs of inflammation affecting the heart muscle.

The treatment for myocarditis depends on the cause and severity of the condition.

Myocarditis can sometimes go away on its own without treatment.

The symptoms of heart failure that can occur due to myocarditis may require treatment for systolic heart failure. This treatment can include diuretics, ACE inhibitors, or beta-blockers.

Learn more about systolic heart failure treatments here.

Other forms of treatment may include:

Taking medications

Doctors may choose to give a person a medication called intravenous (IV) immunoglobulin. They can give a person this medication through an IV line.

Resting

After diagnosis, a person should avoid sports and strenuous activities for around 3–6 months.

However, the duration of their rest time will depend on the recovery of their heart and their doctor’s advice.

Physical exertion could result in death for some people with myocarditis.

However, physical rehabilitation could also help strengthen the heart.

Avoiding certain medications

A person should not take nonsteroidal anti-inflammatory drugs, such as ibuprofen.

They should also avoid any medications that could block the immune system. However, to treat the immune response, a doctor may choose to use corticosteroids.

Trying a heart pump

If a person is experiencing low blood pressure as a result of myocarditis, they may require a temporary artificial heart pump.

Getting a heart transplant

If the heart damage does not get better, and the myocarditis has progressed to advanced stages, a person may require a heart transplant.

There are no specific actions that a person can take to prevent myocarditis.

However, since myocarditis can have viral or bacterial causes, people can take the following steps to reduce their risk of getting an infection:

  • staying away from people who have flu-like symptoms
  • regularly washing the hands
  • using tick repellent
  • wearing clothing that covers the skin as much as possible
  • making sure that all vaccines are up to date, including those for rubella and the flu

The outlook for myocarditis may vary depending on its cause, the severity of the symptoms, and the recovery of heart function.

Myocarditis can heal on its own. A person can recover fully from the condition.

However, in other cases, myocarditis may lead to life threatening complications or long-term consequences.

Myocarditis can cause damage to the heart, which can result in:

These complications can result in death. Therefore, a person should contact a doctor immediately if they believe that they may have myocarditis.

Myocarditis is a rare condition, but it can have serious complications.

It occurs when the muscle of the heart becomes inflamed and weak. This puts additional pressure on the heart to pump blood around the body and can cause severe systemic complications.

Myocarditis can occur due to viral or bacterial infections, among other things. However, sometimes, it seems to have no obvious cause.

The treatment options and outlook will vary according to the symptoms and causes of myocarditis.