Myocarditis
Myocarditis: A Complete Patient Guide
Myocarditis is inflammation of the heart muscle (the myocardium). It is most often caused by a viral infection and can range from a mild illness that settles by itself to, rarely, a serious condition causing heart failure or dangerous heart rhythms. It affects people of all ages and is a recognised cause of chest pain and heart problems in younger adults, including athletes.
The inflammation can weaken the heart’s pumping function and disturb its electrical system. Many people recover completely, while a minority are left with scarring that can cause rhythm problems or a weakened heart over time. When the pericardium is involved too, the condition is called myopericarditis.
Myocarditis has been recognised as a very rare complication of mRNA COVID-19 vaccination (mainly in young men, usually mild and short-lived) and as a more frequent complication of COVID-19 infection itself.
The 2025 ESC guideline on myocarditis and pericarditis sets out a structured approach: diagnosis with cardiac MRI and, in selected cases, biopsy, treatment of heart failure and arrhythmias, targeted treatment of the cause, and guidance on returning to exercise.
Symptoms range from none to severe, and often follow a recent flu-like or gastrointestinal illness by days or weeks.
Common symptoms
Chest pain, which may be sharp or pressure-like, sometimes similar to a heart attack
Breathlessness, particularly on exertion or lying flat
Palpitations or an irregular heartbeat
Unusual fatigue and reduced exercise tolerance
Features of more severe disease
Fainting or near-fainting
Ankle swelling and marked breathlessness (heart failure)
Fever and muscle aches around the time of onset
Mild or silent myocarditis
Many people have mild symptoms that are put down to a viral illness, and some cases are discovered only when tests such as an ECG or troponin are abnormal.
A viral infection is the commonest cause, but many other triggers exist.
Infections
Viruses, including coxsackie, parvovirus B19, adenovirus, influenza and COVID-19
Less commonly bacteria, Lyme disease and parasitic infections such as Chagas disease
Immune and inflammatory causes
Autoimmune conditions such as lupus and sarcoidosis
Giant cell myocarditis and eosinophilic myocarditis (rare)
Immune checkpoint inhibitor cancer treatments, which can cause severe myocarditis
Other triggers
Reactions to some medicines, and toxins such as alcohol and cocaine
Very rarely, vaccination (notably mRNA COVID-19 vaccines in young men)
Factors that may worsen outcomes
Strenuous exercise during active infection or inflammation increases risk, so rest is important.
Chest pain or breathlessness after a viral illness, particularly with palpitations, should be checked rather than waited out.
Arrange a prompt assessment if you have:
Chest pain, palpitations or unusual breathlessness within days to weeks of a viral illness or vaccination
Reduced exercise ability or fatigue that persists after an infection
Known myocarditis with symptoms that return
Ankle swelling or breathlessness lying flat
Call 999 immediately if you have:
Severe or persistent chest pain, particularly with sweating or breathlessness
Fainting or collapse
Severe breathlessness at rest
A very fast or irregular heartbeat with feeling extremely unwell
Myocarditis is diagnosed by combining symptoms with blood tests and heart imaging, and by excluding coronary artery disease.
1. ECG and rhythm monitoring
An ECG may show changes or rhythm disturbances, and cardiac monitoring can detect arrhythmias.
2. Blood tests
Troponin (a marker of heart muscle injury) is usually raised, along with inflammatory markers such as CRP. Tests for infection and autoimmune disease may be added.
3. Echocardiogram
An echocardiogram assesses pumping function, wall motion and fluid around the heart.
4. Cardiac MRI
Cardiac MRI is the key non-invasive test, showing inflammation, swelling and scarring of the heart muscle and helping to confirm myocarditis.
5. Coronary assessment and biopsy
Coronary angiography or CT coronary angiography may be needed to exclude a blocked artery. In severe or unexplained cases, an endomyocardial biopsy helps identify the type of myocarditis and guide specific treatment.
Treatment depends on severity and cause. Many people need only rest and follow-up, while severe cases need hospital care.
Supportive treatment
Rest from strenuous exercise during the acute phase and recovery
Treatment of heart failure with standard medicines (such as ACE inhibitors or ARNI, beta-blockers, MRAs, SGLT2 inhibitors and diuretics) if the heart is weak
Treatment of arrhythmias, with temporary or permanent devices in selected cases
Specific treatments
Immunosuppression (steroids and others) is used for certain types, such as giant cell, eosinophilic, sarcoid or immune checkpoint inhibitor myocarditis, and some chronic inflammatory cases
Most viral myocarditis is not treated with steroids or antivirals unless a specific cause is identified
Anti-inflammatory painkillers such as ibuprofen are used cautiously, as they have not been shown to help in myocarditis
Severe disease
People with severe heart failure, shock or dangerous arrhythmias may need intensive care, mechanical circulatory support and, rarely, transplantation.
Avoid strenuous exercise and competitive sport until your cardiologist confirms recovery. The guideline advises restricting exercise for a period of around 3 to 6 months, with reassessment (usually with echocardiography, rhythm monitoring and MRI) before returning to sport.
Gradual return to activity is advised once you have been cleared, starting gently and building up.
Take medicines exactly as prescribed, including heart failure treatment if you need it.
Report symptoms such as palpitations, fainting, breathlessness or chest pain promptly.
Avoid alcohol and illicit drugs, particularly cocaine.
Follow-up with echocardiography and sometimes MRI is arranged to check recovery.
Vaccination: discuss any future vaccination with your cardiologist if myocarditis followed a previous one.
Support is available from the British Heart Foundation and Cardiomyopathy UK.
Most people with myocarditis, particularly mild, post-viral cases, recover fully within weeks to months.
A minority are left with scarring or a weakened heart, which needs long-term treatment and follow-up.
Severe presentations, such as fulminant, giant cell or eosinophilic myocarditis, carry a higher risk and need specialist care.
Late rhythm problems can occur in people with scarring, so follow-up includes rhythm assessment.
Outlook depends on the cause, severity at presentation, heart function and the extent of scarring on MRI.
Myocarditis is inflammation of the heart muscle, most often caused by a virus.
Symptoms include chest pain, breathlessness, palpitations and fatigue, often after an infection.
It can mimic a heart attack, so chest pain needs urgent assessment.
Diagnosis uses troponin, ECG, echocardiography and cardiac MRI, and sometimes biopsy.
Most people recover fully, but a minority have scarring or a weakened heart.
Avoid strenuous exercise for several months and return only after cardiology review.
Treatment is supportive, with heart failure and rhythm treatment where needed, and immunosuppression for specific types.
Rare cases follow mRNA COVID-19 vaccination, usually mild and short-lived.
Guidelines and sources
This page follows current European guidance:
Schulz-Menger J et al. 2025 ESC Guidelines for the management of myocarditis and pericarditis. European Heart Journal 2025;46:3952-4041.
Caforio ALP et al. Current state of knowledge on aetiology, diagnosis, management, and therapy of myocarditis: a position statement of the ESC Working Group on Myocardial and Pericardial Diseases. European Heart Journal 2013;34:2636-2648.
These are the questions patients most often ask about myocarditis.
What is myocarditis?
Inflammation of the heart muscle, most often caused by a viral infection. It can cause chest pain, breathlessness and palpitations, and ranges from mild to severe.
What are the symptoms of myocarditis?
Chest pain, breathlessness, palpitations, fatigue and sometimes fainting, often following a viral illness. Some people have only mild symptoms.
What causes myocarditis?
Most often a virus, such as coxsackie, parvovirus or COVID-19. Other causes include autoimmune conditions, certain cancer immunotherapies, drugs and toxins. Rarely it follows mRNA COVID-19 vaccination.
How is myocarditis diagnosed?
By symptoms, a raised troponin, ECG, echocardiogram and cardiac MRI, with coronary tests to exclude a heart attack, and sometimes a heart muscle biopsy.
Can you fully recover from myocarditis?
Yes, most people do, particularly after mild viral myocarditis. A minority have lasting scarring or a weakened heart that needs long-term treatment.
When can I exercise again after myocarditis?
Strenuous exercise and competitive sport should be avoided for around 3 to 6 months, with a cardiology assessment (echo, rhythm monitoring and often MRI) before returning. Light activity may be allowed earlier on advice.
Is myocarditis the same as a heart attack?
No. A heart attack is caused by a blocked coronary artery, while myocarditis is inflammation of the heart muscle. They can feel and look alike at first, which is why urgent tests are needed.
Is myocarditis after the COVID vaccine serious?
It is very rare, mostly in young men after the second mRNA dose, and usually mild with a quick recovery. Myocarditis is more common after COVID-19 infection itself. Discuss any concerns with your doctor.
Can I have a private assessment for chest pain or palpitations after a virus?
Yes. A telephone, video or face-to-face consultation in Peterborough or Corby can review your symptoms, with ECG, echocardiography, monitoring and cardiac MRI arranged as appropriate. Severe chest pain needs 999.
- Do I definitely have myocarditis, and what caused it?
- Has my heart function been affected, and is there scarring on MRI?
- Do I need treatment other than rest?
- When can I return to exercise, sport and work?
- What follow-up tests will I need and when?
- Do I need rhythm monitoring or a device?
- Is it safe for me to have future vaccinations?
- Should I avoid anti-inflammatory painkillers, alcohol or other things while I recover?
- What symptoms should make me seek urgent help?
- Will my heart recover fully, and what is my long-term outlook?
How the heart muscle is affected
Myocarditis is inflammation of the heart muscle, most often triggered by a virus. In most people the inflammation settles and heart function returns to normal. In some, scar tissue is left behind, which can cause rhythm problems or a weaker heart later.
What you might notice
Symptoms range from none to severe and often start days or weeks after a viral illness. Because myocarditis can mimic a heart attack, new chest pain needs urgent assessment.
How it is diagnosed and followed up
Diagnosis combines symptoms, blood tests and heart imaging, and excludes a blocked coronary artery. Cardiac MRI is the key scan. Strenuous exercise is avoided for around 3 to 6 months, with a review before returning to sport.
If you have chest pain, palpitations or breathlessness after a viral illness, you may benefit from a telephone consultation or video consultation, or a face-to-face consultation in Peterborough or Corby for a more comprehensive assessment. Severe chest pain needs a 999 call.
Investigations such as ECG, echocardiography, cardiac MRI and cardiac monitoring may be recommended.
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Medically reviewed by Dr Salam Salloum, Consultant Cardiologist. Last updated: . This page is for general information and does not replace personal medical advice.