What You Should Know: Myocarditis

Medically Reviewed by James Beckerman, MD, FACC on November 01, 2022

Myocarditis is inflammation of the heart muscle (myocardium). Exactly how many people are affected is hard to know because it often has no symptoms.

Many people who get myocarditis are otherwise healthy. Many things can lead to it. The best ways to prevent it are to treat infections quickly and take action to prevent them

Viral infection is the most common cause of myocarditis.

When you have one, your body produces cells to fight the virus. These cells release chemicals. If the disease-fighting cells enter your heart, some chemicals they release can inflame your heart muscle.

Some things that can cause myocarditis include:

Fungal and parasitic infections can also cause it.

Other causes include certain chemicals or allergic reactions to medications or toxins like:

An autoimmune disease that causes inflammation throughout your body, like lupus or rheumatoid arthritis, may also lead to myocarditis.

Myocarditis often has no symptoms. In fact, most people recover and never even know they had it.

If you do have symptoms, they may include:

  • Shortness of breath
  • Abnormal heartbeat, which causes fainting in rare cases
  • Light-headedness
  • A sharp or stabbing chest pain or pressure, which may spread to your neck and shoulders
  • Fatigue
  • Signs of infection, such as
  • Painful joints
  • Swollen joints, legs, or neck veins
  • Small amounts of urine

If you have symptoms like these, your doctor will check you for an abnormal or rapid heartbeat, fluid in your lungs, or leg swelling.

Your doctor may order tests such as:

  • Blood tests to check for infection, antibodies, or blood cell counts
  • A chest X-ray so they can see your heart, lungs, and other chest structures
  • An electrocardiogram (EKG) to record your heart's electrical activity
  • A heart ultrasound (echocardiogram) to make an image of your heart and its structures

In a few cases, doctors order cardiac MRI scans or heart muscle biopsies to help confirm it.

Call your doctor right away if you have symptoms of myocarditis. If you have or had an infection, it’s more likely that you have the condition. Seek immediate medical care if your symptoms are severe. If chest pain, trouble breathing, or swelling have gotten worse since you were told you have myocarditis, call 911 or go to the hospital.

If you have myocarditis, your doctor will treat its cause, if possible. They’ll also try to take the extra load off your heart, if needed, and take steps to prevent or control complications.

Usually, you’ll be prescribed medicines to help your heart work better. Examples include:

Your doctor will also probably suggest rest or reduced activity. They’ll probably also put you on a low-salt diet to keep fluid from building up.

You may be hospitalized if you have complications, like a blood clot or weakened heart. If abnormal heart rhythms are severe, you may need other medications, a pacemaker, or an implantable cardioverter-defibrillator (ICD).

Your outlook depends on:

  • What causes your myocarditis
  • Your overall health
  • If you have complications

You may recover completely. Or you may have a chronic condition. Either way, follow-up care can help keep track of any ongoing problems. It's also important to know that myocarditis can recur, although it’s not common.

If left untreated, myocarditis may lead to symptoms of heart failure, where your heart has trouble pumping blood the way it should. In rare cases, it leads to other problems, such as:

Cardiomyopathy : The heart muscle weakens or the structure of the heart muscle changes.

Pericarditis : Inflammation of the sac covering the heart (called the pericardium).

Myocarditis and cardiomyopathy are leading causes of heart transplants in the U.S. In very rare cases, myocarditis can lead to sudden death.

Show Sources


Myocarditis Foundation: "About Myocarditis."

eMedicine: "Myocarditis."

Mount Sinai Cardiovascular Institute and Center for Cardiovascular Health: "Myocarditis."

MedlinePlus: "Myocarditis."

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