What is myocarditis?

Myocarditis is a disease marked by the inflammation of the heart muscle known as the myocardium — the muscular layer of the heart wall. This muscle is responsible for contracting and relaxing to pump blood in and out of the heart and to the rest of the body.

When this muscle becomes inflamed, its ability to pump blood becomes less effective. This causes problems like an abnormal heartbeat, chest pain, or trouble breathing. In extreme cases, it can cause blood clots leading to a heart attack or stroke, damage to the heart with heart failure, or death.

Normally, inflammation is a bodily response to any sort of wound or infection. Imagine when you cut your finger: within a short time, the tissue around the cut swells up and turns red, which are classic signs of inflammation. The immune system in your body is producing special cells to rush to the site of the wound and implement repairs.

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

What causes myocarditis?

In a lot of cases, the exact cause of myocarditis is not found. When the cause of myocarditis is found, it’s usually an infection that has made its way to the heart muscle, such as a viral infection (the most common) or a bacterial, parasitic, or fungal infection.

As the infection tries to take hold, the immune system fights back, trying to get rid of the disease. This results in an inflammatory response that may weaken heart muscle tissue. Some autoimmune diseases, like lupus (SLE), can cause the immune system to turn against the heart, resulting in inflammation and myocardial damage.

It’s often difficult to determine exactly what’s causing the myocarditis, but potential culprits include the following causes.


According to the Myocarditis Foundation, viruses are one of the most common causes of infectious myocarditis. The most common viruses to cause myocarditis include Coxsackievirus group B (an enterovirus), Human Herpes Virus 6, and Parvovirus B19 (which causes fifth disease).

Other possibilities include echoviruses (known to cause gastrointestinal infection), Epstein-Barr virus (causes infectious mononucleosis), and Rubella virus (causes German measles).


Myocarditis can also result from infection with Staphylococcus aureus or Corynebacterium diptheriae. Staphylococcus aureus is the bacterium that can cause impetigo and be a methicillin resistant strain (MRSA). Corynebacterium diptheriae is the bacterium that causes diphtheria, an acute infection that destroys tonsils and throat cells.


Yeast infections, molds, and other fungi can sometimes cause myocarditis.


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

Autoimmune diseases

Autoimmune diseases that cause inflammation in other parts of the body, like rheumatoid arthritis or SLE, can also sometimes cause myocarditis.

What are the symptoms?

The dangerous thing about myocarditis is that it can affect anyone, occur at any age, and may proceed without displaying any symptoms. If symptoms do develop, they often resemble those symptoms one might experience with the flu, such as:

  • fatigue
  • shortness of breath
  • fever
  • joint pain
  • lower extremity swelling
  • achy feeling in the chest

Many times, myocarditis may subside on its own without treatment, much like a cut on your finger eventually heals. Even some cases that go on for a long time may never create sudden symptoms of heart failure.

But, secretly, they may cause damage to the heart muscle where the heart failure symptoms slowly appear over time. In other instances, the heart may be faster at revealing its struggles, with symptoms like chest pain, shortness of breath, heart palpitations, and heart failure.

How is it diagnosed?

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

  • blood testing: to check for signs of infection or inflammation sources
  • chest X-ray: to show chest anatomy and potential signs of heart failure
  • electrocardiogram (ECG): to detect abnormal heart rates and rhythms that may indicate a damaged heart muscle
  • echocardiogram (ultrasound imaging of the heart): to help detect structural or functional issues in the heart and adjacent vessels
  • myocardial biopsy (sampling of heart muscle tissue): in some cases, may be performed during a heart catheterization to allow the doctor to examine a small piece of muscular tissue from the heart

Complications of myocarditis

Myocarditis can possibly cause significant damage to the heart. The body’s immune system response, because of a virus or other infection causing myocarditis, can cause notable damage as can certain chemicals or autoimmune diseases that can cause myocarditis. This can ultimately lead to heart failure and ultimately death. These cases are rare, as most patients who have myocarditis recover and resume healthy heart activity.

Other complications include problems with the heart’s rhythm or rate, heart attack, and stroke. In rare cases, an urgent heart transplant may be necessary.

Myocarditis is also linked to sudden death, with up to 9 percent of autopsies of adults revealing inflammation of the heart muscle. This number jumps to 12 percent for autopsies of young adults showing heart muscle inflammation.

How is myocarditis treated?

Treatment for myocarditis may include:

  • corticosteroid therapy (to help reduce inflammation)
  • cardiac medications, such as a beta-blocker, ACE inhibitor, or ARB
  • behavioral changes, such as rest, fluid restriction, and a low-salt diet
  • diuretic therapy to treat fluid overload
  • antibiotic therapy

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

If your myocarditis continues, your doctor may prescribe a corticosteroid to help reduce inflammation. They’ll also likely recommend rest, fluid restriction, and a low-salt diet. Antibiotic therapy may help treat the infection if you have bacterial myocarditis. Diuretic therapy may be prescribed to remove the excess fluid from the body. Your doctor may also prescribe medications that help the heart work more easily.

Almost all of these treatments work to ease the workload on the heart so it can heal itself.

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

Can it be prevented?

There are no steps to definitely prevent myocarditis, but avoiding serious infections may help. Some of the suggested ways to do so include:

  • practicing safe sex
  • staying up to date with vaccinations
  • proper hygiene
  • avoiding ticks

What is the outlook?

The outlook for myocarditis is mostly positive. The chance of it recurring is thought to be roughly 10 to 15 percent, according to the Myocarditis Foundation. Most people with myocarditis recover and don’t have any long-term adverse effects on their heart.

There is still much to be learned about myocarditis. Doctors believe myocarditis is not inherited and haven’t found any genes indicating that it is.