What Is Myocarditis? Symptoms, Causes, and Treatment

Medically Reviewed By Megan Soliman, MD
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Myocarditis weakens the heart, making it difficult for this vital organ to pump blood effectively to all parts of the body. Myocarditis is characterized by the inflammation of the heart muscle. Although some people with myocarditis do not have symptoms, others experience severe symptoms. In some cases, myocarditis can be life threatening, leading to stroke, heart attack, heart failure, arrhythmias, or heart damage.

In adults ages 50 years and above, males are known to have a higher incidence of myocarditis than females.

According to the National Organization for Rare Disorders, 0.5–3.5% of heart failure hospitalizations result from myocarditis. 

This article discusses myocarditis, including its symptoms, causes, diagnosis, and treatment options, in more detail. 

What is myocarditis?

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Myocarditis refers to the inflammation of the heart muscle, called the “myocardium,” which leads to the weakening of the muscles. 

Inflammation occurs when the body’s immune system responds to infectious agents. It also occurs in autoimmune conditions, including lupus. In such cases, the body attacks itself instead of a foreign body.

Inflammation in the short run is not bad; it is how the body fights infection or heals from an injury. However, when it persists for a long time, it can negatively affect body organs and tissues, causing damage.

Normally, heart muscles contract and relax rhythmically to pump blood into and out of the heart to all parts of the body. However, when the muscles are inflamed, it can affect the heart’s electrical system. This means that the heart’s ability to pump blood becomes affected. 

Ineffective pumping of blood by the heart can lead to other health issues and symptoms such as chest pain, an abnormal heartbeat, fluid buildup and swelling, weakness, and difficulty breathing.

Learn more about heart infections here.

Symptoms of myocarditis

Some cases of myocarditis can be asymptomatic, while other cases cause people to experience symptoms. Some symptoms that people with myocarditis may experience include:

Causes of myocarditis 

In 50% of cases, the exact cause of acute myocarditis is not known. When the exact cause of a condition is not known, a doctor may say that it is idiopathic.

However, in some cases, a doctor can identify the cause of myocarditis. Below are some possible causes of myocarditis. 

Bacterial infections

Myocarditis can be the result of a bacterial infection. Microorganisms that cause diseases may invade the heart muscle, causing direct damage. Examples of bacteria that can cause myocarditis include Corynebacterium diphtheriae and Staphylococcus aureus.

The immune system’s response to the infection can also cause inflammatory reactions that may damage the myocardium.

Autoimmune conditions

Certain autoimmune conditions, such as lupus and rheumatoid arthritis, can cause myocarditis. Autoimmune conditions occur when the body’s immune system attacks healthy cells of the body by mistake. The immune system can mistakenly attack the heart cells, damaging the myocardium.

Medications

The side effects of medications such as antibiotics, antidepressants, heart drugs, diuretics, and benzodiazepines can cause myocarditis. 

That said, it is rare that medications cause myocarditis. Substances such as alcohol and cocaine more commonly lead to this condition.

If you have any disease or chronic health condition, it is best to avoid self-medicating and take all your medications in the right dosage as prescribed by your physician.  

COVID-19

Viruses such as SARS-CoV-2, the flu, adenovirus, herpes, and parvovirus B19 are among the most common causes of myocarditis. SARS-CoV-2 is the coronavirus that causes COVID-19. 

Recent studies suggest that myocardial injuries, including myocarditis, are common among people with COVID-19.

Learn more about the effect of COVID-19 on the heart here.

Vaccines

The Centers for Disease Control and Prevention (CDC) report that some people have experienced myocarditis after receiving the Moderna or Pfizer-BioNTech COVID-19 vaccine.

However, the CDC still recommends COVID-19 vaccines for everyone ages 5 years and above, as they consider COVID-19 a greater risk than its vaccine’s possible side effects.

Learn more about myocarditis and COVID-19 vaccines here.

Other microorganisms

Other microorganisms, including fungi and parasites, can also cause myocarditis.

Parasites that survive by living off other organisms can also cause myocarditis. An example of such a parasite is Trypanosoma cruzi, which causes Chagas disease. Chagas disease can lead to cardiac complications, such as heart failure, an enlarged heart, and myocarditis.

Some tick-borne organisms, including Borrelia burgdorferi, Babesia, and Ehrlichia, can also cause myocarditis.

How long does myocarditis last?

An otherwise healthy person can have myocarditis, and the condition can quickly progress to heart failure. Myocarditis may be acute, lasting for the first 2 weeks, or chronic, lasting for longer than 2 weeks. Recovery may take several months to years, sometimes 3–7 years after treatment.

In some cases, the condition can recur. If this happens, it may cause certain inflammation-related symptoms, such as shortness of breath and chest pain.

How do doctors treat myocarditis?

Mild cases of myocarditis may go away on their own. In more severe cases, however, treatment may be necessary. If myocarditis is treated quickly and appropriately, people can often make a full recovery.

Your doctor may offer you the following treatment options:

  • Medication: Your doctor may prescribe medications for heart problems, such as ACE inhibitors, beta-blockers, and angiotensin receptor blockers. You may also receive IV immunoglobulin and corticosteroids. Corticosteroids help reduce inflammation levels by reducing the intensity of the immune response.
    • It is important to note that doctors usually avoid recommending general immunosuppressant medications, including corticosteroids, as they have not shown clinical benefit unless the myocarditis is due to an autoimmune condition.
  • Diuretics therapy: This will help reduce fluid accumulation.
  • Surgery: Myocarditis that leads to complications such as abnormal heart rhythms and heart failure may need surgery to implant a pacemaker, a ventricular assist device, or a donor’s heart. A ventricular assist device will help your heart pump blood from its lower chambers to other body parts. 
  • Treatment of underlying health conditions: When myocarditis is due to a health condition, such as an autoimmune condition or an infection, your healthcare team may also give you treatments for that concern. 

How do doctors diagnose myocarditis?

To diagnose myocarditis, your doctor will take your medical history, examine you physically, and order some tests to rule out other suspected causes. Some tests they may order include

  • Blood tests: Your doctor may request that the laboratory department carries out blood tests. These may include a complete blood count to check for signs of infection, cardiac troponin to check for damage in the heart tissue, and tests for autoantibodies and C-reactive protein to detect inflammation in the body.
  • Chest X-ray: You may need to undergo a chest X-ray to show the anatomy of the chest and identify any potential heart failure signs.
  • Electrocardiogram: This is a test that measures the heart’s electrical activity. It can indicate when the heart rate is abnormal, which can signify damaged heart muscle.
  • MRI: An MRI scan can examine the heart. It produces high resolution images of the heart’s interior, which doctors can use to detect inflammation in the organ.
  • Myocardial biopsy: This involves taking a small sample of the heart muscle tissue and examining it for signs of myocarditis. 

These tests will help your doctor make a proper diagnosis. 

Summary

A viral infection usually causes myocarditis, but bacteria, fungi, and certain autoimmune conditions can also cause it. Although it may resolve on its own in mild cases, severe cases often require treatment. If a person does not receive treatment on time, myocarditis can damage the heart muscle permanently. 

If you experience any symptoms of myocarditis, it is best to talk with a doctor. They will make a diagnosis and start the right treatment, if necessary.

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Medical Reviewer: Megan Soliman, MD
Last Review Date: 2022 Apr 26
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