Myocarditis: Symptoms, Types, Causes and Treatment

Myocarditis is an inflammatory disease of the heart muscle (myocardium) that can affect anyone, from otherwise healthy children to older adults. Though often underdiagnosed due to its subtle, non-specific symptoms, myocarditis can lead to serious complications, including heart failure and sudden cardiac death. Understanding the symptoms, types, causes, and treatment options is vital for early recognition and effective management.

Symptoms of Myocarditis

When it comes to myocarditis, the symptoms can be deceptive—ranging from mild and flu-like to severe and life-threatening. Many people may not even realize they have a heart issue, as the signs can mimic more common conditions like chest infections or even anxiety. This variability makes awareness and timely diagnosis especially important.

Symptom	Description	Severity Range	Source(s)
Chest Pain	Discomfort or pain in the chest	Mild to severe	1, 2, 5
Dyspnea	Shortness of breath	Mild to severe	1, 2, 5
Palpitations	Irregular, rapid heartbeat	Mild to severe	1, 2, 3
Fatigue	Unusual tiredness or weakness	Mild to severe	2, 3
Heart Failure	Swelling, fluid retention, fatigue	Moderate to severe	1, 4, 8
Arrhythmia	Irregular heart rhythm	Mild to severe	2, 3, 4

Table 1: Key Symptoms of Myocarditis

Common Presenting Symptoms

Myocarditis often presents with non-specific symptoms. Chest pain is one of the most frequent complaints, but it may be mistaken for a heart attack or even heartburn. Dyspnea (shortness of breath) can occur during exertion or even at rest, reflecting the heart's reduced ability to pump effectively 1, 2.

Palpitations—often described as a fluttering or racing heartbeat—are also common and may precede more serious arrhythmias. Fatigue and general malaise are frequent, especially in young, active individuals or athletes, who may notice a reduced exercise capacity, increased resting heart rate, or muscle soreness 3.

Severe Presentations

In more severe cases, myocarditis can rapidly progress to heart failure, with symptoms including:

• Fluid retention (swelling in legs or abdomen)
• Persistent cough
• Marked shortness of breath, especially when lying down

Arrhythmias, including atrial or ventricular irregularities, can be life-threatening and are a leading cause of sudden cardiac death, particularly in young people and athletes 3, 8.

Diagnostic Challenges

The symptoms of myocarditis are notoriously non-specific and can mimic other heart conditions such as acute coronary syndrome or even panic attacks. Electrocardiograms (ECGs) might show changes similar to those seen in heart attacks, while biomarkers like troponin can be normal, further complicating diagnosis 2. This diagnostic ambiguity underscores the importance of advanced imaging and, occasionally, biopsy for confirmation 2, 10.

Types of Myocarditis

Myocarditis is not a one-size-fits-all disease. It manifests in several forms, each with its own underlying mechanisms, clinical course, and management strategies. Recognizing the type of myocarditis can guide both diagnosis and treatment.

Type	Defining Feature(s)	Clinical Course	Source(s)
Lymphocytic	Lymphocyte-dominated inflammation	Most common; variable severity	7, 12, 9
Eosinophilic	Eosinophil-rich infiltration, often allergy	May be fulminant/autoimmune	7, 14, 17
Giant Cell	Multinucleated giant cells, severe course	Rapid progression, poor outcome	7, 17
Fulminant	Rapid onset, severe heart failure/shock	Life-threatening, acute	8, 17
Autoimmune	No infection; immune-mediated	May be chronic or acute	9, 14
Infectious	Viral/bacterial/protozoal/fungal causes	Variable—depends on organism	1, 9, 12

Table 2: Major Types of Myocarditis

Lymphocytic Myocarditis

This is the most common type, especially in developed countries, typically triggered by viral infections. The inflammation is primarily driven by lymphocytes, a type of white blood cell 7, 12. Clinical presentation is highly variable—from mild symptoms to severe heart failure.

Eosinophilic and Giant Cell Myocarditis

Eosinophilic myocarditis often occurs in response to allergies, hypersensitivity reactions, or certain autoimmune diseases, and can be rapidly progressive 7, 14. Giant cell myocarditis is rare but extremely aggressive, characterized by the presence of multinucleated giant cells and a rapid decline in cardiac function, often requiring urgent intervention 7, 17.

Fulminant Myocarditis

Fulminant myocarditis refers to cases with an abrupt, severe onset leading to cardiogenic shock or life-threatening arrhythmias. These patients often require intensive care, mechanical circulatory support, and sometimes heart transplantation 8, 17.

Autoimmune and Infectious Myocarditis

Autoimmune myocarditis occurs without an identifiable infectious trigger and may be isolated or part of systemic autoimmune conditions 9, 14. Infectious myocarditis covers a wide spectrum, with viruses being the predominant cause in most regions, but bacteria, fungi, and protozoa (like Trypanosoma cruzi in Chagas disease) are also implicated 1, 9, 12.

Causes of Myocarditis

The causes of myocarditis are as diverse as its presentations. Understanding the underlying cause is key for tailoring treatment and improving outcomes.

Cause Category	Examples	Geographic/Epidemiologic Notes	Source(s)
Viral	Coxsackievirus, Adenovirus, Parvovirus B19, HHV6	Most common in developed countries	1, 9, 11
Bacterial	Diphtheria, Staphylococcus, Streptococcus	More frequent in developing areas	1, 12
Protozoal	Trypanosoma cruzi (Chagas disease)	Endemic in Latin America	1, 12
Autoimmune	Systemic lupus, sarcoidosis, IIMs	Can occur worldwide	9, 14, 4
Drug-induced	Immune checkpoint inhibitors, antibiotics	Increasing due to new therapies	16, 14
Idiopathic	No clear cause identified	Diagnosis of exclusion	9

Table 3: Main Causes of Myocarditis

Viral Causes

Viruses are the leading cause of myocarditis in most developed countries, with coxsackievirus, adenovirus, parvovirus B19, and human herpesvirus 6 (HHV6) being the most commonly implicated 1, 9, 11. The virus directly damages heart muscle cells, triggering an inflammatory response that can continue even after the virus is eliminated 2, 9.

Bacterial and Protozoal Causes

While less common in developed nations, bacterial myocarditis remains significant in regions with higher rates of diphtheria and other bacterial infections 1, 12. Protozoal infection, particularly by Trypanosoma cruzi, is a major cause in Latin America, leading to chronic Chagas cardiomyopathy 1, 12.

Autoimmune and Drug-Induced Causes

Autoimmune diseases such as systemic lupus erythematosus, sarcoidosis, and idiopathic inflammatory myopathies can cause myocarditis as part of a broader systemic inflammatory process 9, 14, 4. Drug-induced myocarditis is increasingly recognized, especially with the use of modern cancer immunotherapies (immune checkpoint inhibitors), which can lead to severe, sometimes fatal, cardiac inflammation 16, 14.

Idiopathic Myocarditis

In many cases, no specific cause is found, even after extensive testing. These are labeled idiopathic myocarditis, and an autoimmune mechanism is often suspected 9.

Treatment of Myocarditis

Treating myocarditis involves a combination of supportive care, targeted therapies, and sometimes advanced interventions. The approach depends heavily on the underlying cause, severity, and the presence of complications like heart failure or arrhythmia.

Treatment	Purpose/Indication	Notes on Use	Source(s)
Supportive Care	Rest, monitor, manage symptoms	Mainstay for most cases	5, 6, 17
Heart Failure Meds	Beta-blockers, ACE inhibitors, diuretics	For reduced cardiac function	1, 18
Immunosuppression	Steroids, other agents	Autoimmune, giant cell, sarcoid	1, 17, 18
Antivirals/IVIG	For specific viral causes	Limited evidence; select settings	18
Mechanical Support	ECMO, VADs	Fulminant or refractory cases	8, 10, 17
Arrhythmia Management	Antiarrhythmics, ICDs	For serious rhythm disturbances	1, 18
Exercise Restriction	Avoid strenuous activity	For 3-6 months post-diagnosis	5, 3

Table 4: Treatment Options for Myocarditis

Supportive and Symptom-Based Care

For most patients, especially those with mild disease, supportive care is the cornerstone of treatment. This includes:

• Bed rest and avoidance of physical exertion (especially important for athletes)
• Monitoring for arrhythmias and heart failure symptoms
• Fluid management, oxygen, and other symptomatic support as needed 5, 6, 3

Heart Failure and Arrhythmia Management

If myocarditis leads to reduced heart pumping function, standard heart failure medications such as beta-blockers, ACE inhibitors, and diuretics are used. Close monitoring for arrhythmias is essential—antiarrhythmic drugs or implantable devices may be required in severe cases 1, 18.

Immunosuppressive and Immunomodulatory Therapy

Immunosuppression (such as corticosteroids) is recommended for cases where an autoimmune mechanism is identified, or for specific types like giant cell myocarditis and cardiac sarcoidosis 1, 17, 18. In chronic or fulminant autoimmune myocarditis, immunosuppressive treatment has shown benefit in clinical trials 18. However, its use in typical viral myocarditis remains controversial and is generally not recommended unless the virus has been cleared 17, 18.

Antiviral and Intravenous Immunoglobulin (IVIG) Therapy

Specific antiviral therapy is rarely used except in documented viral infections with available treatments. IVIG has shown some promise in viral and inflammatory myocarditis, but evidence is mixed and its use is generally reserved for select cases 18.

Advanced and Mechanical Support

Fulminant myocarditis, which can rapidly progress to severe heart failure or cardiogenic shock, may necessitate advanced interventions like extracorporeal membrane oxygenation (ECMO) or ventricular assist devices (VADs) to support circulation while the heart recovers 8, 10, 17.

Lifestyle and Exercise Recommendations

Patients are advised to avoid strenuous exercise for at least 3 to 6 months after diagnosis, as exertion during recovery increases the risk of arrhythmia and sudden cardiac death 5, 3. Return to sports or intense physical activity should only occur after thorough cardiac evaluation and normalization of cardiac function.

Conclusion

Myocarditis is a complex and often underrecognized disease with a wide range of symptoms, causes, and outcomes. Early recognition and tailored treatment can make a significant difference in prognosis, especially in severe or fulminant cases. Here’s what to remember:

• Symptoms are broad and non-specific, including chest pain, shortness of breath, fatigue, and palpitations.
• Types of myocarditis vary by cause and clinical course, including lymphocytic, eosinophilic, giant cell, fulminant, autoimmune, and infectious forms.
• Causes range from viral and bacterial infections to autoimmune diseases and medications, with viral causes being most common in developed countries.
• Treatment is individualized, ranging from supportive care and heart failure management to immunosuppression, antiviral therapy, and advanced mechanical support in severe cases.

Understanding the diverse presentations and management strategies for myocarditis is critical for clinicians, patients, and families alike—empowering early intervention and the best chance for full recovery.