Myocarditis

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What is myocarditis?

Myocarditis (my-oh-car-DIE-tis) is swelling (inflammation) of the heart’s muscle wall (myocardium). 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 enough blood to itself and the rest of the body. The heart may beat in an abnormal way (arrhythmia), which is sometimes life threatening.

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

What causes myocarditis?

In children, the most common cause of myocarditis is infection from a virus, such as viruses that cause the common cold, influenza or a less common infection. The virus 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. Still, it is quite rare for common childhood infections to lead to myocarditis.

Other causes include other infections, chemicals, radiation, allergic reaction to a medicine and certain diseases that cause inflammation in the body.
Myocarditis after COVID-19 vaccination

Rarely, myocarditis or pericarditis has started in a patient soon after they received a COVID-19 mRNA vaccine, usually within a week after their second dose. Seattle Children’s doctors and researchers are leading work to better understand why this might happen, how to prevent it and how best to care for people who are affected.

Most patients recover well with treatment and feel better quickly. If your child has symptoms of myocarditis or pericarditis after being vaccinated against COVID-19 (or at any time), call your child’s primary care provider.

Learn more on the Centers for Disease Control and Prevention website.

Heart Center at Seattle Children's

Our pediatric cardiologists and cardiac surgeons have more advanced training and experience operating and performing procedures on babies, children and teens than at any other children's hospital in the Pacific Northwest.

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
Poor weight gain or slow growth (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
Skin may look blue or purple tinged, mottled (different shades or colors), grayish or paler than usual; the lips, mouth, gums, fingernails or toenails may look bluish (cyanosis)
Vomiting

Older children may have many of the same symptoms as babies. They 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 child’s doctor will examine your child thoroughly. This includes using a stethoscope to listen to their heart and looking 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:

Chest X-ray
Echocardiography
ECG or EKG (electrocardiogram)
MRI (magnetic resonance imaging)
Cardiac catheterization

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 to fight certain viral infections
Steroids and intravenous immunoglobulins to reduce inflammation
Diuretics to reduce the heart’s workload by helping the kidneys rid the body of extra water
Standard medicines for heart failure if your child’s heart muscle is very weak
Blood-thinning medicine to prevent blood clots

We may treat an arrhythmia with medicines or by implanting 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.

Ventricular assist device

Along with 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. They are a form of mechanical circulatory life support. We use them 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 a heart transplant if the heart does not recover enough.
Extracorporeal membrane oxygenation (ECMO)

ECMO is a form of heart-lung bypass used to pump oxygen-rich blood when your child’s heart or lungs do not function properly or need to rest. Like VADs, ECMO provides support that may help in a child with myocarditis. The ECMO machine draws oxygen-poor blood through a thin tube (cannula) into a device that removes excess carbon dioxide and adds oxygen. Then the device pumps the oxygen-rich blood into an artery in your child’s body. Read more.
Transplant

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.

Myocarditis at Seattle Children’s

The experts you need are here
- The Heart Center team includes more than 40 pediatric cardiologists who diagnose and treat every kind of heart problem. We have treated many children with myocarditis.
- We use state-of-the-art methods to diagnose myocarditis accurately and plan the best care.
- Our doctors and surgeons are experts in the treatments your child may need, including medicine, a pacemaker or defibrillator, a ventricular assist device or a heart transplant.
- We also have a pediatric cardiac anesthesia team and a Cardiac Intensive Care Unit ready to care for children who have heart surgery. General anesthesia is a medicine we give to people before surgery so they are fully asleep during the procedure.
- Your child’s team includes other experts from Seattle Children’s based on their needs, like neonatologists or pulmonologists.
Care from birth through young adulthood
- Seattle Children’s cardiologists see babies, children and teens with myocarditis. We have experience diagnosing and treating this condition in kids of all ages.
- Your child’s treatment plan is custom-made. We plan and carry out their treatment based on the specific details of their illness.
- We closely check your child to tell if they have any lasting heart damage and to make sure they get the care that is right for them at every age.
Support for your whole family
- We are committed to your child’s overall health and well-being and to helping your child live a full and active life.
- Whatever types of care your child needs, we will help your family through this experience. We will discuss your child’s condition and treatment options in ways you understand and involve you in every decision.
- Our Child Life specialists know how to help children understand their illnesses and treatments in ways that make sense for their age.
- Seattle Children’s has many resources, from financial to spiritual, to support your child and your family and make your experience as smooth as possible.
- Many children and families travel to Seattle Children’s for heart surgery or other care. We help you coordinate travel and housing so you can stay focused on your child.
- Read more about the supportive care we offer.
Advancing treatment for children
- Seattle Children’s doctors are working to advance treatment for myocarditis and enhance the quality of life for children with this condition.
- Yuk Law was lead author of the American Heart Association’s 2021 scientific statement on diagnosing and managing myocarditis in children. Doctors around the world use this publication to help guide the care they provide.