What Is Myocarditis? Understanding Heart Muscle Inflammation

Myocarditis, at its core, is an inflammation of the heart muscle, medically termed the myocardium. This condition can significantly impair your heart’s ability to effectively pump blood throughout your body. While some individuals might experience only mild symptoms or none at all in the early stages, myocarditis can manifest with noticeable signs such as chest pain, shortness of breath, and irregular heart rhythms.

In many instances, a viral infection is the culprit behind myocarditis. However, it’s also important to note that reactions to certain medications or underlying conditions causing widespread inflammation in the body can also trigger this heart condition.

If left unaddressed or in severe cases, myocarditis can severely weaken the heart. This weakening can lead to insufficient blood circulation, potentially causing blood clots to form within the heart. These clots pose serious risks, as they can travel to the brain, leading to a stroke, or block heart arteries, resulting in a heart attack.

Fortunately, myocarditis is a treatable condition. Treatment strategies range from medications to more intensive procedures or even surgeries, depending on the severity and underlying cause of the myocarditis.

Recognizing the Symptoms of Myocarditis

The presentation of myocarditis can vary widely. Some people, particularly in the early stages, may not experience any noticeable symptoms. Others might have mild symptoms that are easily dismissed as general malaise.

Common symptoms associated with myocarditis can include:

Chest Pain: This can range from a sharp, stabbing pain to a dull ache or pressure in the chest.
Fatigue: Unusual and persistent tiredness or lack of energy.
Swelling (Edema): Noticeable swelling in the legs, ankles, and feet due to fluid retention.
Arrhythmias: Experiencing rapid, fluttering, or irregular heartbeats. These are also known as heart rhythm abnormalities.
Shortness of Breath (Dyspnea): Difficulty breathing, which can occur both at rest and during physical activity.
Lightheadedness or Fainting (Syncope): Feeling dizzy or as if you might pass out.
Flu-like Symptoms: General symptoms that mimic the flu, such as headache, body aches, joint pain, fever, or sore throat.

It’s crucial to be aware that myocarditis symptoms can sometimes mimic those of a heart attack. Therefore, unexplained chest pain combined with shortness of breath should always be treated as a medical emergency. Seek immediate medical attention if you experience these symptoms.

Myocarditis Symptoms in Children

Myocarditis in children can present with slightly different symptoms compared to adults. Parents and caregivers should be vigilant for the following signs in children:

Breathing Difficulties: Noticeable struggle or labored breathing.
Rapid Breathing: Breathing faster than normal for their age.
Chest Pain: While harder for younger children to articulate, look for signs of discomfort or chest clutching.
Arrhythmias: Rapid or irregular heartbeats.
Fainting: Loss of consciousness.
Fever: Elevated body temperature.

When to Seek Medical Advice

It is imperative to contact a healthcare professional if you or your child experience any symptoms suggestive of myocarditis. Again, symptoms of myocarditis can overlap with those of a heart attack, making prompt medical evaluation essential.

Seek emergency medical help immediately if you experience unexplained chest pain, rapid heartbeats, or shortness of breath. Do not delay in seeking help if you are experiencing severe symptoms; go to the nearest emergency room or call for emergency medical services.

Uncovering the Causes of Myocarditis

Myocarditis can arise from a variety of causes, with infections being a primary trigger.

Viral Infections: A wide range of viruses are known to be associated with myocarditis. These include common viruses like adenovirus (responsible for the common cold) and the COVID-19 virus. Other implicated viruses include hepatitis B and C viruses, parvovirus B19 (causing fifth disease, a mild rash illness), and herpes simplex virus. Gastrointestinal infections from echoviruses, Epstein-Barr virus (causing mononucleosis), and rubella (German measles) can also lead to myocarditis. Additionally, HIV, the virus causing AIDS, is another viral cause.
Bacterial Infections: Certain bacteria can also induce myocarditis. Examples include staphylococcus, streptococcus, and the bacteria responsible for diphtheria and Lyme disease.
Parasitic Infections: Parasites like Trypanosoma cruzi and toxoplasma are known causes of myocarditis. Some parasites are transmitted through insect bites and can lead to Chagas disease, which is more prevalent in Central and South America but can occur in the United States.
Fungal Infections: Fungal infections can cause myocarditis, especially in individuals with compromised immune systems. These include yeast infections like candida, molds such as aspergillus, and histoplasma (often found in bird and bat droppings).

Beyond infections, myocarditis can also be triggered by:

Medications and Illicit Drugs: Certain medications, such as some cancer drugs, antibiotics (like penicillin and sulfonamide drugs), and anti-seizure medications, can cause drug-induced myocarditis. Cocaine is another substance known to potentially lead to myocarditis.
Chemicals and Radiation: Exposure to substances like carbon monoxide or radiation can, in some cases, result in myocarditis.
Underlying Health Conditions: Certain autoimmune and inflammatory conditions are associated with myocarditis. These include lupus, Wegener’s granulomatosis, giant cell arteritis, and Takayasu’s arteritis.

In many instances, despite thorough investigation, the exact cause of myocarditis remains unidentified. These cases are classified as idiopathic myocarditis.

Potential Complications of Myocarditis

While many cases of myocarditis resolve without long-term issues, severe myocarditis can lead to lasting damage to the heart muscle and serious complications.

Possible complications of myocarditis include:

Heart Failure: Untreated myocarditis can weaken the heart muscle to the point where it cannot effectively pump blood, leading to heart failure. In severe cases of myocarditis-related heart failure, individuals may require a ventricular assist device (VAD) or even a heart transplant.
Heart Attack and Stroke: Damage to the heart muscle can disrupt normal blood flow and promote clot formation within the heart chambers. If a blood clot obstructs a coronary artery, it can cause a heart attack. Similarly, if a clot from the heart travels to an artery supplying the brain, it can cause a stroke.
Arrhythmias (Irregular Heartbeats): Myocardial damage can disrupt the heart’s electrical system, leading to various arrhythmias. Certain types of arrhythmias significantly increase the risk of stroke and other cardiovascular events.
Sudden Cardiac Death: In the most severe scenarios, myocarditis can trigger life-threatening arrhythmias that cause the heart to stop beating abruptly, resulting in sudden cardiac arrest. If untreated, this can lead to sudden cardiac death.

Strategies for Myocarditis Prevention

Currently, there is no specific way to completely prevent myocarditis. However, adopting preventive measures to minimize the risk of infections can be beneficial.

General preventative steps include:

Avoid Contact with Sick Individuals: Limit close contact with people who are exhibiting symptoms of illness, especially respiratory infections like the flu or common cold, until they have recovered. If you are sick, take precautions to prevent spreading germs to others.
Practice Frequent Handwashing: Regular and thorough handwashing with soap and water is a highly effective way to prevent the spread of infections.
Avoid Risky Behaviors: To reduce the risk of HIV-related myocarditis, practice safe sex and avoid intravenous drug use.
Stay Up-to-Date on Vaccinations: Ensure you receive recommended vaccinations, including those that protect against COVID-19, influenza, and rubella – all of which are diseases that can potentially cause myocarditis. It’s important to note that, in rare instances, the COVID-19 vaccine has been linked to myocarditis and pericarditis (inflammation of the outer lining of the heart), particularly in young males aged 12 to 29. Discuss the benefits and risks of vaccines with your healthcare provider.

By Mayo Clinic Staff

Myocarditis care at Mayo Clinic

Request an appointment

Diagnosis & treatment

June 04, 2024

References

AskMayoExpert. Myocarditis. Mayo Clinic; 2021.
Cooper LT. Clinical manifestations and diagnosis of myocarditis in adults. https://www.uptodate.com/contents/search. Accessed March 23, 2022.
Ammirati E, et al. Management of acute myocarditis and chronic inflammatory cardiomyopathy. Circulation. 2020; doi:10.1161/CIRCHEARTFAILURE.120.007405.
Cooper LT. Myocarditis: Causes and pathogenesis. https://www.uptodate.com/contents/search. Accessed March 23, 2022.
Siripanthong B, et al. Recognizing COVID-19-related myocarditis: The possible pathophysiology and proposed guideline for diagnosis and management. Heart Rhythm. 2020; doi:10.1016/j.hrthm.2020.05.001.
Ferri FF. Myocarditis. In: Ferri’s Clinical Advisor 2021. Elsevier; 2021. https://www.clinicalkey.com. Accessed March 23, 2022.
Cooper LT. Treatment and prognosis of myocarditis in adults. https://www.uptodate.com/contents/search. Accessed March 23, 2022.
Allan CK, et al. Clinical manifestations and diagnosis of myocarditis in children. https://www.uptodate.com/contents/search. Accessed March 23, 2022.
Bonow RO, et al., eds. Myocarditis. In: Braunwald’s Heart Disease: A Textbook of Cardiovascular Medicine. 11th ed. Elsevier; 2019. https://www.clinicalkey.com. Accessed March 23, 2022.
Nguyen LS, et al. Systematic analysis of drug-associated myocarditis reported in the World Health Organization pharmacovigilance database. Nature Communications. 2022; doi:10.1038/s41467-021-27631-8.
Healthy habits to help prevent flu. Centers for Disease Control and Prevention. https://www.cdc.gov/flu/prevent/actions-prevent-flu.htm. Accessed March 23, 2022.
Cooper LT, et al. The role of endomyocardial biopsy in the management of cardiovascular disease: A scientific statement from the American Heart Association, the American College of Cardiology, and the European Society of Cardiology. Circulation. 2007;116:2216.
Ami TR. Allscripts EPSi. Mayo Clinic. March 29, 2024.
Mankad R (expert opinion). Mayo Clinic. April 13, 2022.
Cheng CY, et al. Myocarditis in systemic immune-mediated diseases: Prevalence, characteristics and prognosis. A systematic review. Autoimmunity Reviews. 2022; doi:10.1016/j.autrev.2022.103037.
Lopez-Jimenez F (expert opinion). Mayo Clinic. Nov. 29, 2021.
Myocarditis and pericarditis after mRNA COVID-19 vaccination. Centers for Disease Control and Prevention. https://www.cdc.gov/coronavirus/2019-ncov/vaccines/safety/myocarditis.html. Accessed April 13, 2022.
Hause AM, et al. Safety monitoring of COVID-19 vaccine booster doses among persons aged 12–17 years — United States, December 9, 2021-February 20, 2022. MMWR Morbidity and Mortality Weekly Report. 2022; doi: 10.15585/mmwr.mm7109e2.
Mouch SA, et al. Myocarditis following COVID-19 mRNA vaccination. Vaccine. 2021; doi:10.1016/j.vaccine.2021.05.087.
Mevorach D, et al. Myocarditis after BNT162b2 mRNA vaccine against Covid-19 in Israel. The New England Journal of Medicine. 2021; doi:10.1056/NEJMoa2109730.
Lee ASY, et al. Myocarditis following COVID-19 vaccination: A systematic review (October 2020-October 2021). Heart, Lung and Circulation. 2022; doi:10.1016/j.hlc.2022.02.002.
COVID-19: Get the facts. Mayo Clinic. https://www.mayoclinic.org/diseases-conditions/coronavirus/in-depth/coronavirus-vaccine/art-20484859. Accessed April 14, 2022.
Laham RJ. Intraaortic balloon pump counterpulsation. https://www.uptodate.com/contents/search. Accessed April 16, 2024.