What is myocarditis?

Myocarditis is a term for inflammation of the heart muscle, the myocardium. Myocarditis can reduce the ability of the heart to pump and may lead to heart failure in severe cases. The most common cause of myocarditis is a viral infection.

Other causes of myocarditis may include:[1][2][3]

  • Bacteria
  • Parasites
  • Autoimmune conditions, such as type 1 diabetes and lupus
  • Certain medications, such as clozapine, amitriptyline and lidocaine
  • Illicit drug use
  • Excessive alcohol consumption
  • Chemotherapy[4]
  • Radiation therapy

Myocarditis can affect anyone of any age, but it most commonly occurs in otherwise healthy young people.[1][2] It is slightly more prevalent in men than women.[5] In 2013, there were 1.5 million reported cases of myocarditis around the world, or approximately 22 instances for every 100 000 people.[6]

Myocarditis may be mild, causing few or no symptoms, or severe, causing life-threatening heart failure. Where present, symptoms may include fatigue, a dip in performance during physical activity, chest pain, fever, rapid heartbeat, shortness of breath, palpitations and swelling of the legs.[1][2]

Many cases of viral myocarditis clear up on their own within a few days or weeks, leaving no negative health effects. Treatment typically involves bed rest and avoiding physical exercise for several months. Other types of myocarditis may require treatment with antibiotics or steroids. In some cases, the condition may persist or recur and can cause serious complications. Treatment with heart medications, a pacemaker and surgery may sometimes be necessary.[1]

Myocarditis symptoms

The symptoms of myocarditis vary widely, and some people do not present with any heart-related symptoms at all. In these cases, myocarditis may be detected when an ECG (electrocardiogram) test shows abnormalities.

The main symptoms of myocarditis may include:[1][2][3]

  • Fatigue - more than half of those affected complain of this symptom - and a dip in performance during physical activity
  • Chest pain or pressure - over one third complain of this symptom
  • Fever
  • Shortness of breath
  • Palpitations
  • Rapid heartbeat
  • Irregular heartbeat (cardiac arrhythmia)

The affected person may also present with lightheadedness, fainting and swelling of the legs. The symptoms depend on the cause of the inflammation, as well as its severity. If any symptoms are present and myocarditis is suspected, medical advice should be sought immediately. In some cases, myocarditis can cause sudden death.

Causes of myocarditis

Viruses are the most common cause of myocarditis. The Coxsackie virus is one of the most frequently implicated in Western Europe and North America,[6] but many other viruses can trigger myocarditis, including:[1][2][3]

  • Parvovirus B-19 (fifth disease)
  • Adenovirus (common cold)
  • Influenza
  • Human herpes virus 6
  • Epstein-Barr (glandular fever)
  • Rubella (German measles)
  • Varicella (chicken pox)
  • Mumps
  • Measles
  • Enteroviruses
  • Hepatitis A and C
  • HIV

Myocarditis may develop while the viral infection is present or shortly afterwards.

Bacterial infection, most commonly diphtheria, may also cause myocarditis.[3] In addition, Lyme disease, Chagas’ disease caused by infection with the protozoan organism Trypanosoma cruzi via insect bites in tropical countries,[1] and various other parasites, bacteria and fungi can cause myocarditis.

Other myocarditis causes include:[1][3]

  • Allergic reactions to medications
  • Heavy metal poisoning
  • Exposure to other poisons
  • Exposure to radiation
  • Excess alcohol
  • Electric shock
  • Rejection of the heart following a heart transplant
  • Illicit drug use, such as amphetamines and cocaine

Though rare, myocarditis may also result as a complication of other conditions, such as type 1 diabetes. Very rarely, a condition called idiopathic giant cell myocarditis may occur. It is typically seen in otherwise healthy young adults, though it may be associated with inflammatory bowel disease. In giant cell myocarditis, which is often fatal,[7] abnormal cells develop in the heart muscle.

Diagnosis of myocarditis

After taking the medical history of the affected person and performing a physical examination, a doctor will typically request an ECG, sometimes called an EKG, to assess the functioning of the heart muscle (myocardium). They may also order blood tests to look for infections and certain conditions, as well as markers of inflammation.[1][2][8]

A chest X-ray may be requested to check the size and shape of the heart and whether there is any fluid buildup, pulmonary edema being a sign of heart failure. A heart ultrasound scan (echocardiogram) may also be requested.[1][2][8] In addition, the doctor may arrange a heart MRI to assess tissue damage.[3]

Occasionally, an endomyocardial biopsy may be performed. This entails removing a small tissue sample from the heart and testing it to determine the cause(s) of the myocarditis.[1][3][8] Endomyocardial biopsy and cardiac MRI are the preferred diagnostic tests for distinguishing myocarditis from other conditions that affect the heart.[9]

Prevention of myocarditis

While it is difficult to prevent myocarditis, taking steps to prevent the spread of viral, bacterial and other types of infections may help to reduce the risk.

Measures to prevent myocarditis include:

  • Staying home when ill and avoiding physical exertion
  • Washing hands regularly
  • Taking precautions when traveling

Diphtheria immunization may prevent diphtheria-related myocarditis.[10] Avoiding the use of illicit drugs, excessive use of alcohol and exposure to poisonous substances may also lower the risk of developing myocarditis.

Treatment of myocarditis

Myocarditis treatment depends on the cause and the severity of the symptoms. People who have been diagnosed with myocarditis should rest and avoid physical exertion, including athletic activities, for several months to avoid straining the heart muscle. A medical practitioner will be able to advise when exercise can be resumed safely. In addition, tobacco and alcohol should be avoided. Painkillers and anti-inflammatory medication may be prescribed for the management of fever, chest pain and discomfort. If the symptoms of myocarditis are mild, no other treatment may be needed.[1][3][10]

Where possible, the underlying cause of the myocarditis should be addressed. Antibiotics may be prescribed to treat a bacterial infection, while steroids may be needed to treat giant cell myocarditis.[1] If an autoimmune condition is implicated, this should be treated.[8]

Where myocarditis symptoms are severe, hospitalization may be necessary. People presenting with heart failure and cardiac arrhythmias may require treatment with the following:[10]

  • Oxygen
  • Diuretics, vasodilators and other medication to treat heart failure
  • Anticoagulants to prevent blood clots
  • Medication or, in some cases, a pacemaker to treat arrhythmia
  • A defibrillator[2]

Some of these treatments may need to be continued to support the heart and blood pressure until the myocardium recovers.

In many cases, myocarditis clears up on its own, without any complications or long-term health effects. However, sometimes the heart sustains damage, leaving a degree of heart failure that requires lifelong treatment.[1] This may involve lifestyle changes and chronic medication.[8] In cases where the damage to the heart muscle is severe, a heart transplant may be necessary.[1]

Myocarditis can be fatal. Death may occur if the condition worsens after diagnosis and becomes unresponsive to treatment. It may also occur suddenly where acute myocarditis has a rapid onset.[1]

Dilated cardiomyopathy

A possible complication of myocarditis, dilated cardiomyopathy is a condition where the heart becomes chronically enlarged and cannot pump blood efficiently.[2] The myocardium dilates, stretching and becoming thinner. As a result, the heart weakens, and heart failure may occur. Dilated cardiomyopathy may also cause arrhythmias, blood clots and heart valve problems.[11]

The risk of developing dilated cardiomyopathy from myocarditis is low. It is estimated that only two in 10 000 people develop this condition. Dilated cardiomyopathy typically affects adults between 20 and 60 years of age, and it is more common in males. A genetic predisposition may be present.[12]

Symptoms range from none to heart failure, stroke, arrhythmias and sudden cardiac death. Doctors may use chest X-rays, ECG tests and echocardiograms, among other tests, to diagnose dilated cardiomyopathy.[12]

Treatment is the same as for heart failure and may involve diuretics (water pills), beta-blockers (blood pressure medication), anticoagulants (blood thinners) and other medications, as well as pacemakers and defibrillators, among other possibilities. In cases where dilated cardiomyopathy does not respond to treatment, a heart transplant may be required.[12]

Myocarditis FAQs

Q: Myocarditis vs. pericarditis - what is the difference?
A: Myocarditis is an inflammation of the myocardium, or heart muscle. Pericarditis, on the other hand, is an inflammation of the pericardium - two thin layers of sac-like tissue that surround the heart. Myocarditis and pericarditis are two separate heart conditions.[13]

Q: Can children get myocarditis?
A: Yes, children and infants can get myocarditis. However, pediatric myocarditis is uncommon. Myocarditis is typically acute or fulminant (severe and rapid in onset) in children and may be a cause of sudden death. The most common cause of myocarditis in children is a viral infection.[14]

Other names for myocarditis

  • Heart muscle inflammation
  • Inflammatory cardiomyopathy

  1. Patient. “Myocarditis.” January 24, 2017. Accessed August 17, 2017.

  2. Myocarditis Foundation. “About Myocarditis.” Accessed August 17, 2017.

  3. Patient. “Myocarditis.” January 24, 2017. Accessed August 18, 2017.

  4. Journal of Clinical Medicine Research. “Chemotherapy Induced Cardiomyopathy: Pathogenesis, Monitoring and Management.” March 24, 2009. Accessed February 20, 2018.

  5. Current Problems in Cardiology. “Sex and Gender Differences in Myocarditis and Dilated Cardiomyopathy.” January, 2013. Accessed August 17, 2017.

  6. UpToDate. “Etiology and pathogenesis of myocarditis.” July 28, 2017. Accessed August 17, 2017.

  7. The New England Journal of Medicine. Idiopathic Giant-Cell Myocarditis - Natural History and Treatment.” June 26, 1997. Accessed August 21, 2017.

  8. Texas Heart Institute. “Myocarditis.” August, 2016. Accessed August 21, 2017.

  9. National Center for Biotechnology Information. “Myocarditis in the differential diagnosis of cardiomyopathies. Endomyocardial biopsy or MRI?” June, 2015. Accessed August 22, 2017.

  10. Harvard Health Publications. “Myocarditis.” December, 2012. Accessed August 22, 2017.

  11. American Heart Association. “Dilated Cardiomyopathy (DCM).” February 20, 2017. Accessed August 23, 2017.

  12. Patient. “Dilated Cardiomyopathies.” June 16, 2014. Accessed August 23, 2017.

  13. American Heart Association. “What is Pericarditis?” July 5, 2016. Accessed August 23, 2017.

  14. UpToDate. “Clinical manifestations and diagnosis of myocarditis in children.” November 23, 2015. Accessed August 23, 2017.