FAQ – Types of Myocarditis
What are the clinical classifications of myocarditis?
A: There are several different types of myocarditis, classified based on their causes and the nature of inflammation.The heart muscle, (myocardium), gets inflamed from a variety of reasons with viruses being the main cause in many parts of the world. This inflammation can impair the heart’s ability to pump blood and can lead to a variety of symptoms, ranging from mild to severe.
Viral Myocarditis
Cause: Viral infections are the most common cause of myocarditis, often stemming from viruses such as the Coxsackievirus, adenovirus, parvovirus B19, and more recently, SARS-CoV-2 (COVID 19).
Description: Viral myocarditis occurs when a virus infects the heart muscle, triggering an inflammatory response. In many cases, the body’s immune system attacks the virus, but this process can also inadvertently damage the heart tissue. The symptoms can range from mild (such as fatigue and shortness of breath), to severe (like chest pain and heart failure). If left misdiagnosed or untreated, it can lead to dilated cardiomyopathy or chronic heart failure.
Treatment: The treatment is mainly symptomatic in nature. Cardiac Rest for 3 to 6 months is very important to allow the heart to heal. That means: no exercise, no lifting weights, no sports. Simple walking on flat surfaces for short periods of time is usually allowed once feeling better, but this is dependent on your specific case and your cardiologist. Cardiac rest is very important so that the heart muscle can work on doing what it needs to do to keep the person alive, and not be pushed to work harder than it needs to during that 3-6 month period.
Treatment may also include antiviral medications, anti-inflammatory drugs, Possibly antihypertensives, antiarrhythmic meds, and heart failure therapies, may be utilized if needed. In severe cases, patients may require mechanical support for the heart or even a heart transplant.
Giant Cell Myocarditis
Cause: The exact cause of Giant Cell Myocarditis is unknown, but it is thought to be an autoimmune condition. It is often associated with other autoimmune diseases, such as Crohn’s disease or Rheumatoid Arthritis.
Description: Giant Cell Myocarditis is a rare but aggressive form of myocarditis characterized by widespread inflammation and the presence of multinucleated giant cells within the heart muscle. This type can cause rapid heart failure, ventricular arrythmias, and is frequently life-threatening without prompt treatment.
Treatment: Immunosuppressive therapy is typically required to control the inflammation. Heart failure therapies, mechanical support, or a heart transplant may be necessary in severe cases.
Bacterial Myocarditis
Cause: Bacterial infections, including those caused by Staphylococcus, Streptococcus, Borrelia (Lyme disease), or Corynebacterium diphtheriae (diphtheria), can lead to bacterial myocarditis.
Description: Bacterial myocarditis occurs when bacteria infect the myocardium directly or release toxins that cause inflammation. The heart muscle can be damaged either through the infection itself or through the immune response. This type is rarer than viral myocarditis and can result in serious complications like heart failure, arrythmias, or septic shock.
Treatment: Antibiotics are the mainstay of treatment, targeting the specific bacterial cause. Supportive care for heart function is often necessary, and in severe cases, more intensive cardiac support may be required.
Fungal Myocarditis
Cause: Fungal infections like Candida, Aspergillus, and Histoplasma can cause myocarditis, especially in immunocompromised individuals (e.g. those with HIV/AIDS, cancer patients, or organ transplant recipients).
Description: Fungal myocarditis occurs when fungi invade the heart muscle, leading to inflammation. It is rare and typically affects individuals with weakened immune systems. The disease can be severe, leading to heart failure, systemic infection, and other complications.
Treatment: Treatment focuses on antifungal medications to clear the infection, and supportive care to manage heart function.
Autoimmune Myocarditis (Immune-Mediated)
Cause: This type of myocarditis occurs when the immune system mistakenly attacks the heart muscle, often in conjunction with autoimmune diseases such as Lupus, Rheumatoid Arthritis, or Sarcoidosis.
Description: Autoimmune myocarditis is characterized by inflammation that arises from an abnormal immune response, which damages heart tissue. It may also be triggered by certain medications, including chemotherapy or immune checkpoint inhibitors used in cancer treatment. Symptoms can vary, but they often include chest pain, fatigue, and signs of heart failure.
Treatment: Treatment typically involves immunosuppressive therapies such as corticosteroids or other immunomodulatory drugs to reduce the immune response. Heart failure treatment may also be necessary.
Toxic Myocarditis
Cause: Toxic Myocarditis can occur due to exposure to certain drugs, chemicals, or toxins. Some common causes include alcohol, illegal stimulants, chemotherapy drugs, and snake venom.
Description: In Toxic Myocarditis, the heart muscle becomes inflamed due to a direct toxic effect or a hypersensitivity reaction to a substance. Symptoms vary depending on the severity of exposure but can include chest pain, fatigue, and signs of heart failure. In the case of drug-induced myocarditis, stopping the offending substance can lead to significant improvement.
Treatment: The primary approach is to eliminate exposure to the toxin and provide supportive care. In some cases, specific treatments for heart failure or arrhythmias may be needed.
Lymphocytic Myocarditis
Cause: Lymphocytic Myocarditis is most commonly viral in origin but can also occur with autoimmune disorders or drug reactions.
Description: This type of myocarditis is characterized by the presence of lymphocytes (a type of white blood cell) in the heart muscle tissue, indicative of an immune response. It can vary in severity from mild to life-threatening, causing symptoms like chest pain, heart palpitations, and heart failure.
Treatment: Treatment depends on the underlying cause and may include antiviral therapies, anti-inflammatory drugs, and heart failure medications.
Can myocarditis be confused with other heart diseases?
A: Yes. For example, the symptoms of heart failure, including shortness of breath, fatigue, inability to tolerate exercise, and associated with difficulty breathing while laying down/sleeping are common to many heart diseases besides myocarditis. One feature that distinguishes myocarditis from other causes of heart failure is that it often follows an upper respiratory or gastrointestinal infection and is due to a specific immune response against the heart itself.
Myocarditis can also mimic a heart attack. When cardiac inflammation occurs in the regions of the heart nearest to the outside surface, it can present as chest pain. However, in myocarditis, the coronary vasculature, which supplies the heart and is generally blocked in heart attacks, usually appears normal1.
Myocarditis can cause arrhythmias caused by defects in the conduction system of the heart. When the conduction (electrical) system in the heart experiences “blocks”, it is unable to coordinate pumping blood adequately. Loss of blood perfusion to the brain can result in “passing out”. Cardiac sarcoidosis and infections with Lyme disease, and Diphtheria are associated with these types of defects (see FAQ of types of viruses and bacteria that cause myocarditis for disease details).
What is a biopsy and when is it used in the diagnosis of myocarditis?
A: A biopsy is performed when myocarditis is suspected and when making the diagnosis of myocarditis may impact treatment options or prognosis (expected outcomes as in life-threatening outcomes). It is recommended that if a patient has an indication (reason) for an endomyocardial biopsy and they are at a medical center where this expertise is unavailable, the patient should be transferred to a medical center with this expertise.
What does it mean to diagnose something by histology?
A: Many disease processes occur on the microscopic level and cannot be seen by other means. In order to see what is going on in tissue, physicians will look at finely cut and stained tissue sections to identify the disease process present. This involves looking at the types of cells present and their shapes and spatial orientation. The disease process in myocarditis can only be diagnosed by histological investigation of very small pieces of heart tissue (biopsies).
How is heart tissue collected to evaluate it by histology?
A: Heart tissue is collected by an endomyocardial biopsy to get very small pieces of tissues that can be analyzed histologically. It is collected by accessing the blood vessels connected to the heart. Briefly, the internal jugular vein or femoral vein (the large veins in the front of the neck or leg) are accessed and a bioptome is guided to the right side of the heart.
With the advent of flexible bioptomes, access through the femoral veins (the large veins in the groin) can equally allow access to the right heart. Endomyocardial biopsies are generally performed under the guidance of imaging techniques that allow the visualization of the bioptome in the vessels and heart. In addition to being used in the diagnosis of myocarditis, endomyocardial biopsies are used for the diagnosis of transplant rejections 3.3.
Based on established recommendations in the 2007 American Heart Association/American College of Cardiology/European Society of Cardiology (AHA/ACC/ESC) scientific statement on endomyocardial biopsies 2, samples are taken from more than one region in the right ventricle (5-10 samples taken). At least 4-5 samples should be submitted for light microscopic examination (lower power magnifications). The samples can sometimes be examined under very high power magnification using transmission electron microscopes, which can help identify certain adverse drug reactions and metabolic diseases.
What are the histological classifications of myocarditis?
A: Interpretation of endomyocardial biopsy samples is guided by the Dallas criteria by physicians that developed a working standard for diagnosing myocarditis 4.
- Active myocarditis is defined as “an inflammatory infiltrate of the myocardium with necrosis and/or degeneration of adjacent myocytes not typical of the ischemic damage associated with coronary heart disease”.-Interpretation: There are small inflammatory cells that are found in the heart that are causing damage to the heart itself. These cells include monocytes and neutrophils and occasionally eosinophils, each with roles in killing infections and infected cells.
- Borderline myocarditis is diagnosed when the inflammatory infiltrate is sparse and injury to the heart cells themselves (myocytes) is not demonstrated.
Conclusion
Myocarditis can take many forms, each with different causes, severity, and treatment approaches. Understanding the type of myocarditis you or a loved one is diagnosed with is crucial for developing an effective treatment plan. Early diagnosis and consultation with a healthcare professional are key in managing the condition and preventing long-term damage to the heart.
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