Myocarditis is inflammation of the heart muscle called myocardium. This inflammation can affect the heart's ability to pump blood and may interfere with its electrical system, causing abnormal heart rhythms.
Myocarditis can develop after an infection, particularly a viral infection, but it may also result from autoimmune diseases, certain medicines, toxins and other inflammatory conditions. Some people experience only mild symptoms and recover completely, while severe cases can lead to heart failure, irregular heartbeat or cardiogenic shock.
Inflammation of the heart muscle can sometimes occur together with inflammation of the pericardium, the membrane surrounding the heart. When both are involved, the condition may be described as myopericarditis.
In this article, Begin Health Life explains myocarditis symptoms, causes, diagnosis and treatment so it can help people recognize warning signs and seek medical care when necessary.
What Causes Myocarditis?
There are several possible myocarditis causes, and sometimes the exact trigger cannot be identified.
Viral and Other Infections
Viral infections are important causes of myocarditis. Several viruses have been associated with inflammation of the heart muscle, including viruses responsible for respiratory and systemic infections.
Influenza, COVID-19 and other viral illnesses can occasionally be followed by myocardial inflammation. In some cases, the virus may directly injure heart cells, while in others the body's immune response contributes to tissue damage.
Other infectious causes can include certain bacterial, fungal and parasitic infections.
Autoimmune and Inflammatory Diseases
Myocarditis may occur when the immune system attacks healthy tissues or becomes excessively activated.
Some autoimmune and systemic inflammatory diseases can affect the heart muscle. In these situations, treating the underlying inflammatory condition may be an important part of management.
Medicines and Other Triggers
Certain medicines can rarely cause inflammatory reactions involving the heart. Some cancer treatments, particularly immune checkpoint inhibitors, have been associated with myocarditis because they stimulate immune activity.
Certain toxins and other harmful exposures may also damage cardiac tissue causing myocarditis.
How Does Myocarditis Develop?
After an infectious or other trigger, heart muscle cells may become injured. The immune system responds by releasing inflammatory chemicals and activating immune cells.
In some people, this immune response becomes excessive or continues after the original trigger has disappeared. Persistent inflammation can damage myocardial cells and, during healing, may leave areas of fibrosis or scar tissue.
This combination of myocardial injury, inflammation and immune activity can reduce heart function and increase the risk of abnormal heart rhythms.
Myocarditis Symptoms
Myocarditis symptoms vary considerably. Some people have mild or no noticeable symptoms, while others develop symptoms that resemble a heart attack or severe heart failure.
Common symptoms include:
- Chest pain or discomfort
- Shortness of breath
- Fatigue and weakness
- Reduced exercise tolerance
- Rapid or irregular heartbeat
- Heart palpitations
- Lightheadedness
- Fainting
- Swelling of the legs, ankles or feet
- Fever
- Headache
- Muscle or joint aches
Some people develop flu-like symptoms before cardiac symptoms appear.
Chest pain may result from inflammation of the heart muscle itself or from inflammation of the surrounding tissues. Shortness of breath may occur when inflammation reduces the heart's pumping ability.
Because these symptoms can have many causes, symptoms alone cannot confirm myocarditis.
How Is Myocarditis Diagnosed?
Diagnosing myocarditis can be challenging because it may resemble other cardiovascular conditions. A healthcare professional may use several tests.
Electrocardiogram
Electrocardiogram like ECG or EKG records the electrical activity of the heart. It can detect abnormal rhythms and other changes associated with cardiac inflammation.
However, a normal ECG does not completely rule out myocarditis.
Blood Tests
Blood testing may be used to identify signs of inflammation or heart muscle injury.
Cardiac troponin is particularly important because elevated troponin can indicate damage to heart muscle cells. However, troponin can also rise in other forms of cardiac injury, so it cannot by itself diagnose myocarditis.
Echocardiogram
An echocardiogram uses ultrasound to evaluate the structure and function of the heart.
It can show how effectively the heart pumps blood and may identify reduced heart function, abnormal heart-wall movement or fluid around the heart.
Cardiac MRI
Cardiac magnetic resonance imaging (CMR) is an important non-invasive test for suspected myocarditis.
MRI can provide detailed information about myocardial inflammation, swelling, tissue injury and fibrosis.
Endomyocardial Biopsy
In selected severe or unusual cases, doctors may perform an endomyocardial biopsy. A very small sample of heart muscle is collected and examined under laboratory conditions.
A biopsy is not necessary for every patient, but it can help identify specific forms of myocarditis, particularly when the result could change treatment.
Myocarditis Treatment
There is no single treatment for every case of myocarditis. Myocarditis treatment depends on its cause, severity and effect on heart function.
Mild cases may require:
- Rest and reduced physical activity
- Monitoring of heart function
- Treatment of symptoms
- Appropriate medicines when necessary
- Regular medical follow-up
If myocarditis causes heart failure, doctors may prescribe medicines that reduce the workload on the heart or control excess fluid.
Depending on the patient's condition, myocarditis treatment medications may include:
- Diuretics
- Beta blockers
- ACE inhibitors
- ARBs or
- Other guideline-directed heart failure medicines
Medicines may also be used to control abnormal heart rhythms or reduce the risk of blood clots in selected patients.
Does Myocarditis Require Steroids?
Not everyone with myocarditis needs corticosteroids or other immune-suppressing medicines.
Immunosuppressive treatment may be appropriate for certain immune-mediated forms, such as cases associated with autoimmune myocarditis. It is not automatically appropriate for every case of suspected viral myocarditis.
Treatment should therefore be based on the suspected cause and clinical findings.
Severe Myocarditis
Severe myocarditis can be caused by autoimmune reactions, toxins, medications and viral infections like flu. The severe form may cause:
- Acute heart failure
- Serious arrhythmias or
- Cardiogenic shock
Patients with severe disease may need hospitalization and continuous cardiac monitoring.
In life-threatening cases, advanced treatments may be required like intravenous medicines, mechanical circulatory support, heart function assist devices. Heart transplantation may be considered in exceptional cases where severe heart damage does not recover.
How Long Does Myocarditis Last?
Myocarditis recovery varies from person to person. It may take from 2 weeks to several months depending upon the severity of the heart inflammation.
Some patients recover completely, while others may experience persistent symptoms or reduced heart function. Severe inflammation can sometimes leave scar tissue in the heart.
Importantly, feeling better does not always mean that the heart has completely recovered. Follow-up testing may therefore be necessary before returning to normal levels of strenuous physical activity.
People diagnosed with myocarditis are generally advised to avoid intense exercise and competitive sports during recovery. The timing of a safe return to exercise should be determined by a healthcare professional.
Can Myocarditis Cause Permanent Heart Damage?
Many people recover without significant long-term problems, but severe or persistent myocarditis can cause complications.
Possible myocarditis complications include:
- Heart failure
- Dilated cardiomyopathy
- Persistent abnormal heart rhythms
- Blood clots
- Stroke
- Long-term reduction in heart function
- Sudden cardiac death in severe cases
Myocarditis and Influenza
Influenza mainly affects the respiratory system, but in rare cases it can be associated with complications involving other organs, including the heart.
Myocarditis and flu may therefore occur together or sequentially. A person recovering from influenza who develops new chest pain, unexplained shortness of breath, fainting or significant palpitations should not automatically assume these symptoms are simply part of the flu.
However, most people with influenza do not develop myocarditis. Chest symptoms during an infection can have many other causes.
Myocarditis vs. Heart Attack
Myocarditis and a heart attack can both cause chest pain, but their underlying mechanisms are different.
A heart attack usually occurs when blood flow through a coronary artery becomes severely restricted, causing ischemic damage to heart muscle. Myocarditis involves inflammation of the heart muscle and can occur without a blocked coronary artery.
Because the symptoms can overlap, medical testing is important when unexplained chest pain occurs.
When Should You Seek Medical Care?
Seek urgent medical attention if you develop:
- New or severe chest pain
- Severe or worsening shortness of breath
- Fainting or near-fainting
- A very rapid or irregular heartbeat
- Severe weakness
- New swelling of the legs or feet
- Difficulty breathing while resting
- Symptoms suggesting severe heart failure
Chest pain accompanied by shortness of breath, fainting or significant palpitations should be taken seriously, particularly when it occurs during or shortly after an infection.
Myocarditis Prevention
There is no guaranteed way to prevent every case of myocarditis because it has many possible causes. However, general measures that reduce infection and exposure risks may be helpful:
- Keep recommended vaccinations up to date.
- Practice regular hand hygiene.
- Avoid close contact with people who are acutely ill.
- Follow appropriate treatment for infections.
- Manage autoimmune and inflammatory diseases with medical guidance.
- Avoid illicit drugs and known cardiotoxic substances.
- Discuss potential medication reactions with a healthcare professional.
People receiving treatments known to have a potential risk of myocarditis may require appropriate heart monitoring.
Final Takeaways
Myocarditis is inflammation of the heart muscle that can range from a mild condition to a life-threatening cardiovascular disease.
Viral infections are important triggers, but myocarditis causes can also include autoimmune diseases, certain medicines, toxins and other inflammatory conditions.
Most importantly, chest pain, shortness of breath, fainting or significant heart palpitations require prompt medical evaluation, particularly when they occur during or after an infection.
Most people with mild myocarditis can recover, but severe disease may cause heart failure, dangerous arrhythmias or cardiogenic shock. Begin Health Life recommends avoiding intense exercise during the recovery and attending recommended follow-up appointments.