What is Myocarditis?

What is Myocarditis?

Myocarditis is a rare condition that causes inflammation of the heart muscle. The heart muscle swells and weakens, diminishing the heart’s ability to properly pump blood to the rest of the body and may increase the risk of blood clots and strokes. 

Myocarditis affects the myocardium, the middle muscular layer of the heart. The pericardium is the thin sac-like membrane that surrounds the outside of the heart, and the endocardium is the smooth, innermost layer of tissue that lines the chambers and valves inside the heart. Inflammation that affects the pericardium is known as pericarditis, and inflammation of the endocardium is called endocarditis. 

Myocarditis, pericarditis, and endocarditis can be caused by viral, bacterial, and fungal infections, and all three should be treated promptly to avoid further health complications.

Types of Myocarditis


There are different types of myocarditis:

  • Acute myocarditis - characterized by a rapid onset and usually caused by a viral infection. It can affect a person at any age, including infants and teens.
  • Chronic myocarditis - describes ongoing inflammation of the heart muscle. This can occur when treatment takes longer than usual or when symptoms reappear after treating acute myocarditis. It may also be caused by autoimmune disorders, as the body’s immune cells continue to attack healthy tissue, leading to chronic inflammation.
  • Lymphocytic myocarditis -a rare type of myocarditis and occurs when immune cells called lymphocytes accumulate around the heart muscle tissue, causing inflammation. Hospitalization may be required to treat this type of myocarditis.
  • Giant cell myocarditis - a very rare and life-threatening type of myocarditis that occurs when inflammation and damage to the heart muscle is caused by giant cells or masses that form from immune cells that fuse together.

Signs and Symptoms of Myocarditis


Many people do not experience signs or symptoms of myocarditis. Some individuals may experience a general feeling of illness but do not know that the illness is heart-related.

Adult myocarditis symptoms may include:

  • Viral infection, such as fever, body aches, sore throat, headache, vomiting, or diarrhea
  • Chest pain
  • Shortness of breath
  • Heart arrhythmias, including rapid or abnormal heart rhythms
  • Swelling of the legs, ankles, or feet
  • Fatigue
  • Lightheadedness

Myocarditis in Children

Children may or may not exhibit symptoms of myocarditis. When children experience symptoms, they are often more severe in newborns and children younger than age two.

Symptoms of myocarditis in children may include:

  • Viral infection symptoms, including fever, body aches, sore throat, headaches, vomiting, or diarrhea
  • Difficulty feeding
  • Unexplained weight loss
  • Rapid breathing
  • Fatigue and sleeping more than usual
  • Cold hands and feet, due to poor circulation
  • Fussy, distressed behavior
  • Swelling of the face, legs, or feet
  • Abdominal pain or nausea, due to swelling of the liver
  • Chest pain
  • Heart palpitations or an irregular heartbeat

It is not unusual for myocarditis to go unnoticed in children. In many cases, the condition is not diagnosed until the child has a severe case or develops a heart arrhythmia. 

Regular pediatric care, including check-ups and keeping your doctor informed about any changes in your child’s health, such as abdnormal behavior or noticeable symptoms, can help detect heart conditions like myocarditis. Learn more about our team of pediatric experts and our pediatric care services.

What Causes Myocarditis?


Myocarditis is rare, and in many cases, the cause is not determined. Often, it is caused by an infection in the body, but there are non-infectious situations that could also lead to myocarditis. 

Possible causes of myocarditis include:

  • Viral infections - the most common cause of myocarditis in children and adults, this includes viruses such as the common cold, influenza (flu), COVID-19, hepatitis B and C, parvovirus, adenovirus, and coxsackie virus
  • Bacterial infections - caused by the bacteria that cause strep, staph infections, Lyme Disease, diphtheria, toxic shock syndrome, and Rocky Mountain spotted fever
  • Parasites - including insects that cause infections such as toxoplasmosis and Chagas disease. Toxoplasmosis infection comes from a rather common parasite and usually occurs from eating undercooked meats or being exposed to infected cat feces. The parasites that cause Chagas disease exist in the southern part of the U.S., though they are much more common in South and Central American countries.
  • Fungi - such as molds or the fungi found in bird droppings can cause infections that lead to myocarditis, particularly in immunocompromised people 
  • Chemical or radiation exposure - including exposure to toxic chemicals such as arsenic or carbon monoxide, radiation, or venom from spiders or snakes
  • Autoimmune diseases - such as lupus, Kawasaki disease, or sarcoidosis, may trigger inflammation of the heart and cause myocarditis
  • Certain medications or drugs – such as antibiotics, anti-seizure medication, and drugs used to treat cancer, as well as certain illegal drugs like cocaine and MDMA

When myocarditis is caused by an infection, most of the heart’s inflammation is triggered by the body’s immune system response to the infection, rather than the pathogen itself.

Myocarditis and the COVID-19 vaccine

After receiving the COVID-19 vaccine, some recipients reported experiencing myocarditis, with a higher incidence found in male adolescents and young adults, usually within a week of receiving the vaccination. While this is a rare complication and most of the patients fully recovered with treatment, the CDC is still investigating the long term effects of myocarditis after receiving the COVID-19 vaccine. 

The CDC continues to recommend the vaccine for individuals at age five or older, as infection with COVID-19 can lead to more heart problems than those caused by the vaccine.

Myocarditis Risk Factors

Risk Factors

There are multiple factors that may increase your risk of myocarditis. Some are beyond your control whereas others are related to medical treatments or existing medical conditions.

General risk factors for myocarditis include:

  • Young adults –  all ages can be affected by myocarditis, but young adults may have an increased risk of developing the condition
  • Males – even though it is reported more often in men, women may also experience myocarditis
  • Poor reactions to inflammation – although it is not an inherited condition, an individual’s genes may influence how the body handles inflammation which may lead to myocarditis
  • Excessive alcohol consumption
  • Illicit drug use

Medical treatments that increase your risk of myocarditis include:

  • Radiation therapy
  • Certain antibiotics (penicillin, sulfonamides)
  • Certain anti-seizure medications
  • Dialysis
  • Implantable heart devices
  • Previous heart treatments
  • Central venous catheter use
  • Certain cancer treatment medications

Medical conditions that can increase your risk of getting myocarditis include:

  • Chest injury
  • Diabetes
  • Viral infections (COVID-19, Influenza, Common Cold)
  • Autoimmune diseases
  • Eating disorders
  • Kidney disease
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Trust NewYork-Presbyterian for Myocarditis Care

At NewYork-Presbyterian, our heart care experts and cardiology specialists are experienced in the treatment of myocarditis and provide a full range of personalized care. Learn more about available treatment options for myocarditis care and improve your heart health.

NewYork-Presbyterian provides comprehensive treatment for endocarditis and pericarditis and other conditions that cause heart inflammation with multidisciplinary services by a strong team of national leaders in cardiac care.