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Overview

What Is Myocarditis?

Myocarditis is inflammation of the heart muscle. This inflammation can make it harder for the heart to pump blood and may affect its normal rhythm. Myocarditis can affect people of different ages and may be mild or severe. In some cases, it develops during or after an infection, while other causes may not be identified.

Symptoms

Myocarditis Symptoms

  • Chest pain or pressure.
  • Shortness of breath, especially with activity or when lying down.
  • Unusual or persistent fatigue.
  • A fast or irregular heartbeat (arrhythmia).
  • Fainting or feeling as though you may faint.
  • Swelling in the legs, ankles, or feet.
  • Flu-like symptoms, such as fever, body aches, or feeling unwell.

Seek urgent care

Do not ignore serious symptoms

Chest pain, severe shortness of breath, fainting, or a sustained rapid or irregular heartbeat requires urgent medical evaluation. These symptoms can have causes other than myocarditis, including other emergencies, so seek immediate help rather than waiting for them to pass.

Causes

Myocarditis Causes

Infections and immune reactions

Infections are a common suspected trigger of myocarditis, particularly viral infections. Viral myocarditis may occur while an infection is active or after the immune system responds to it; other infections, including some bacterial, fungal, or parasitic infections, can also be involved. COVID-19 has been associated with heart inflammation in some people, but the risk and cause vary, and myocarditis should be assessed by a clinician. Myocarditis is not usually spread directly from one person to another.

  • Autoimmune diseases can cause the immune system to mistakenly attack heart tissue and trigger inflammation.
  • Certain medicines or drugs may cause an immune reaction or direct injury that affects the heart muscle.
  • Toxins, including some chemical substances, can damage heart muscle and lead to inflammation.
  • Radiation treatment involving the chest can sometimes injure the heart and contribute to inflammation.
  • Rare inherited or inflammatory conditions can make the heart more vulnerable to myocarditis.
  • Lymphocytic myocarditis describes a pattern of immune cells seen in a biopsy; it is not a separate cause by itself.

Myocarditis affects the heart muscle, while pericarditis affects the thin sac surrounding the heart. The two conditions can occur together, sometimes called myopericarditis or perimyocarditis, when inflammation involves both areas. In some people, no clear cause is found.

Risk Factors

Risk Factors for Myocarditis

  • A recent viral or other infection may increase the likelihood of heart muscle inflammation.
  • Autoimmune or inflammatory diseases can increase the risk because of abnormal immune activity.
  • Exposure to certain medicines, nonprescribed drugs, or toxins may raise the risk of heart injury.
  • Some cancer treatments or radiation involving the chest can affect the heart muscle.
  • Inherited conditions or other diseases that affect the heart may increase susceptibility.
  • Myocarditis can occur without an obvious risk factor, so the absence of these factors does not rule it out.

Some factors may be reduced, such as avoiding nonprescribed drugs and discussing possible medication reactions with a clinician before making changes. Other factors, including age, inherited conditions, past illnesses, or a necessary medical treatment, cannot be changed. Having a risk factor does not mean that a person will develop myocarditis.

Complications

Myocarditis Complications

  • Heart failure can develop if inflammation weakens the heart’s ability to pump blood.
  • Abnormal heart rhythms may cause palpitations, dizziness, fainting, or, rarely, life-threatening complications.
  • Blood clots can form when the heart pumps poorly and may travel to cause a stroke or other blockage.
  • Cardiogenic shock can occur when the heart suddenly cannot pump enough blood to support the body.
  • Dilated cardiomyopathy may cause the heart chambers to enlarge and remain weaker over time.

Why follow-up matters

Severity can change the risk

Complications are more concerning when symptoms are severe, heart function is reduced, or abnormal rhythms occur. Prompt evaluation helps clinicians identify these problems and choose appropriate treatment. Follow-up may still be important after symptoms improve.

Diagnosis

How Myocarditis Is Diagnosed

Clinicians review symptoms, recent infections, medicines, medical history, and possible exposures before performing a physical examination. They also consider and rule out other causes of chest pain, breathlessness, or abnormal heart rhythms. The evaluation may include several tests because symptoms and test findings can vary.

  • An ECG or EKG records the heart’s electrical activity and may show rhythm or other electrical changes.
  • Blood tests can look for signs of heart muscle injury and inflammation.
  • An echocardiogram uses ultrasound to assess heart structure, pumping strength, and blood flow.
  • Cardiac MRI can show inflammation, swelling, and injury patterns in the heart muscle.
  • A chest X-ray or other chest imaging may be used when clinicians need to assess the heart, lungs, or other possible causes.
  • Cardiac catheterization may measure pressures and blood flow or help rule out blocked coronary arteries in selected cases.
  • A heart muscle biopsy may be considered in selected serious or unclear cases, but it is not needed for everyone.

For example, myocarditis ECG or myocarditis EKG findings may suggest an abnormal rhythm or other heart changes, while blood tests and imaging can provide evidence of injury or inflammation. No single test confirms every case of myocarditis. Clinicians combine test results with symptoms, examination findings, and the overall medical history.

Treatment & Management

Myocarditis Treatment and Management

Care depends on the cause and severity

  • Selected mild cases may be managed with observation, rest, and follow-up testing while the heart recovers.
  • Medicines may be used to treat heart failure symptoms or control abnormal heart rhythms.
  • ACE inhibitors or related medicines may support heart function when reduced pumping strength or heart failure is present.
  • Antibiotics or other targeted treatments are used only when a specific infection or cause calls for them.
  • Blood-thinning treatment may be considered when blood clots or a high clot risk is present.
  • Treatment for inflammation may be appropriate in selected cases, depending on the cause and the clinician’s assessment.

Severe myocarditis may require hospitalization, continuous heart monitoring, or mechanical circulatory support if the heart cannot pump adequately. Rarely, a heart transplant may be considered for irreversible, advanced heart failure. Do not start, stop, or change medicines without guidance from a clinician, because the safest myocarditis treatment depends on the individual cause and heart function.

Activity during recovery

Return to exercise gradually

Return to exercise and sports should be individualized after follow-up testing and clinician clearance. Strenuous activity may increase risks while the heart is inflamed or recovering, even if symptoms have improved.

Outlook and Prognosis

Outlook and Prognosis

Acute myocarditis may resolve over weeks or months, especially when heart function is preserved and the underlying trigger is addressed. Some people, however, develop persistent reduced heart function, recurrent inflammation, or chronic cardiomyopathy. Recovery varies widely, so an individual outlook cannot be predicted from symptoms alone.

  • The severity of heart muscle injury can affect recovery and the risk of lasting problems.
  • Heart pumping function is an important factor in assessing outlook.
  • Abnormal rhythms can increase the risk of complications and influence monitoring needs.
  • The underlying cause may affect treatment choices and recovery.
  • The heart’s response to treatment helps clinicians refine the prognosis over time.

Follow-up appointments and repeat heart testing may be needed to check rhythm, pumping function, and signs of ongoing inflammation. These checks can help guide medicines, activity restrictions, and the timing of a return to normal activities. Feeling better does not always mean that the heart has fully recovered.

When Should You See a Doctor

When Should You See a Doctor?

Call emergency services

Get immediate help for severe symptoms

Seek emergency care for severe or persistent chest pain, severe trouble breathing, fainting, new confusion, blue or gray lips, or a rapid or irregular heartbeat with weakness or dizziness. Do not drive yourself if you may be having a serious heart problem.

  • Arrange prompt medical evaluation for new, unexplained chest discomfort.
  • Seek medical advice for new or worsening shortness of breath.
  • Contact a clinician about repeated or persistent palpitations.
  • Arrange evaluation after fainting or an unexplained near-fainting episode.
  • Discuss unusual fatigue that begins after an infection, especially when it limits normal activities.
  • Contact a clinician about new swelling in the legs, ankles, or feet.

People with a known or suspected infection, autoimmune condition, or possible medicine reaction should contact a clinician promptly if heart-related symptoms develop. Symptoms of myocarditis can overlap with other urgent conditions, so it is safer to be assessed than to assume the cause.

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