What is myocarditis?

Myocarditis (pronounced my-oh-car-DIE-tis) is inflammation of the myocardium, the heart’s muscle wall. This muscle contracts to pump blood out of the heart and then relaxes as the heart refills with blood.

Myocarditis can weaken your child’s heart muscle. If this becomes severe, the heart cannot pump blood well to the rest of the body.

Blood clots can also form in the heart because blood is not moving through the heart well. Clots are dangerous because they can travel through the bloodstream to a small blood vessel and block the blood flow.

In some cases, myocarditis causes lasting damage to the heart muscle, known as cardiomyopathy.

  • In children, the most common cause of myocarditis is a viral infection, such as influenza or the common cold. The virus itself can get into the heart and damage the muscle. Cells from the body’s immune system can also damage the heart muscle as they fight the infection. However, it is still quite rare for common childhood infections to lead to myocarditis. We cannot predict which person who is infected will go on to develop myocarditis.

    Other causes include other kinds of infections, chemicals, radiation, allergic reaction to a medicine and certain diseases that cause inflammation in the body.

Myocarditis at Seattle Children’s

Consistently ranked one of the nation's best cardiology and cardiac surgery programs by U.S. News and World Report.

  • With more than 40 pediatric cardiologists, we have experience diagnosing and treating every kind of heart problem.

    Our heart team has treated many children with myocarditis. We use state-of-the-art methods to diagnose myocarditis accurately and formulate the most appropriate treatment plan.

    Seattle Children’s has been treating children since 1907. Our team members are specially trained in their fields and in meeting the unique needs of children. For example, the doctors who give your child anesthesia are board certified in pediatric anesthesiology. This means they have extra years of training in how to take care of kids. Our child life specialists know how to help children understand their illnesses and treatments in ways that make sense for their age.

  • When you come to Seattle Children’s, a whole team of people work together to care for your child. Along with your child’s heart doctor (cardiologist), you are connected with neonatologists, pulmonologists (lung doctors), cardiac intensivists, cardiac surgeons, respiratory therapists, nurses, child life specialists, social workers and others, if their expertise is needed.

    We’re committed to your child’s overall health and well-being. We’ll discuss treatments in ways you can understand and involve you in every decision.

    Read more about the supportive care we offer.

Symptoms of Myocarditis

A baby with myocarditis may have these symptoms: 

  • Fever
  • Fast heartbeat or arrhythmia
  • Fast breathing
  • Trouble feeding or working hard to breathe when feeding
  • Failure to thrive
  • Being restless or irritable
  • Sweating more than normal
  • Having little energy or not taking interest in anything
  • Not putting out as much urine as normal
  • Having pale or bluish hands and feet (cyanosis)
  • Vomiting 

Older children may also have a cough, nausea, abdominal or chest pain and swelling in their legs, feet and face. They may be more tired than normal. 

Diagnosing Myocarditis

To diagnose this condition, your doctor will examine your child, use a stethoscope to listen to their heart and look for signs of infection or heart failure.

The doctor will ask for details about any symptoms your child has, their health history and your family health history.

Your child will need tests that provide more information about how their heart looks and works. These may include: 

Your child will also need polymerase chain reaction (PCR) testing, a blood test to check for infections.

Treating Myocarditis

Your child may need 1 or more of these medicines: 

  • Antimicrobials can fight infections caused by a selected few viruses, if identified.
  • Steroids and intravenous immunoglobulins may be used to reduce inflammation.
  • Diuretics help the kidneys rid the body of extra water. This reduces the heart’s workload.
  • If your child’s heart muscle is very weak, they will need standard medicines used to treat heart failure.
  • If your child gets a blood clot in their heart, they will need blood-thinning medicine. 

An arrhythmia may be treated with medicines or by inserting a pacemaker or a defibrillator.

You will need to reduce your child’s activity level for a while and give them a low-salt diet. These steps can make the heart’s work easier.

If your child develops cardiomyopathy, they may need other treatment.

  • In addition to the therapies described above, at Seattle Children’s we are using the latest tools to help the heart pump when it is failing. These tools are called ventricular assist devices, a form of mechanical circulatory life support, and are used in only the most severe forms of myocarditis and cardiomyopathy. They can help allow the heart to rest and also serve as a bridge to heart transplantation if the heart does not recover enough.

  • The heart transplant team at Seattle Children’s performs many transplants each year for children with cardiomyopathy or other heart problems that cannot be controlled using other treatments. Read more about our heart transplant program.

    Julie’s Story – From Failing Heart to Transplant (Video. 5:40)

    When myocarditis suddenly threatened her life, Julie traveled from Hawaii to Seattle Children’s to receive a HeartMate II ventricular assist device (VAD). The VAD kept Julie healthy enough to wait for a heart transplant -- and gave her the chance to build her first snowman.

Contact Us 

Contact the Heart Center at 206-987-2515 to request an appointment, a second opinion or more information.

Providers, see how to refer a patient.