Myocarditis

Disease Description (Causes and Symptoms)

• Definition: Myocarditis is a disease involving inflammation and necrosis of the myocardium (heart muscle), which can lead to reduced cardiac function and ventricular remodeling. Except for some fulminant forms, it often causes acute heart failure followed by recovery; however, if it progresses chronically, it may develop into dilated cardiomyopathy.
• Main causes
  • Viral infection (most common: coxsackievirus, adenovirus, parvovirus B19, etc.)
  • Medications (hypersensitivity reactions) or toxic substances
  • Autoimmune diseases (e.g., systemic lupus erythematosus, Sjögren syndrome, etc.)
  • Special forms: eosinophilic myocarditis, giant cell myocarditis, etc.
• Pathophysiology: Infection or an immune response damages myocardial cells and causes infiltration by inflammatory cells, resulting in reduced contractility, arrhythmias, and ventricular remodeling.
• Main symptoms
  • Chest pain (similar to myocardial ischemia), shortness of breath, fatigue
  • Palpitations (tachycardia, ventricular arrhythmias), syncope
  • In severe cases, cardiogenic shock and acute heart failure

Treatment Methods

• Diagnosis-based principles: Endomyocardial biopsy (EMB) is important for identifying the cause and determining the treatment approach (e.g., whether to use immunosuppressants). Cardiac magnetic resonance imaging (CMR) is useful for noninvasive diagnosis.
• Acute-phase/supportive treatment
  • Hospitalization and monitoring (electrocardiographic monitoring, hemodynamic observation) — especially in cases of heart failure, hypotension, or severe arrhythmias
  • Heart failure medications: ACE inhibitors (or ARB/ARNI), beta-blockers, mineralocorticoid receptor antagonists (MRA), diuretics, etc. — when reduced contractility is clear, apply standard treatment principles for heart failure with reduced left ventricular ejection fraction
  • Patients with acute cardiogenic shock or severe cardiac dysfunction: consider diuretics and inotropes (as needed), such as dopamine/dobutamine
  • Mechanical circulatory support: ECMO, temporary LV assist devices (such as Impella) — prepare for and apply these when the left ventricular ejection fraction is extremely low or tissue hypoxia/severe arrhythmias are present
• Cause-specific treatment
  • Viral myocarditis: Symptomatic treatment is the main approach, and specific antiviral medications are generally not recommended (evidence is limited). Consider immunosuppressive treatment when there is no evidence of a virus on biopsy.
  • Immune-mediated (autoimmune) or biopsy-proven giant cell/eosinophilic myocarditis: Consider high-dose steroids and additional immunosuppressants (e.g., cyclophosphamide) — giant cell myocarditis has a poor prognosis and requires prompt consideration of immunotherapy and transplantation.
  • IVIG (intravenous immunoglobulin): Used in some children and selected adults, but evidence is limited.
• Arrhythmia management
  • If there is a risk of ventricular tachycardia or cardiac arrest, consider antiarrhythmic medications, electrical defibrillation, and, if necessary, temporary or permanent defibrillator implantation (e.g., ICD)
  • Indications for ICD: Long-term protection is needed when LVEF remains low (e.g., ≤35%) despite optimal treatment and a risk of serious arrhythmias remains
• Thrombosis prevention
  • Consider anticoagulant treatment when an intraventricular thrombus is suspected or there is severe hypocontractility
• Lifestyle management and precautions
  • Avoid strenuous physical activity: Usually avoid strenuous exercise and competitive sports for at least 3–6 months (this period may be extended depending on the patient’s condition), and resume activities after reassessment following recovery
  • Cardiac function assessment is necessary when planning pregnancy or surgery
  • Vaccination and infection prevention: Consider preventive recommendations for specific infections (e.g., influenza)

Checkpoints Before an Outpatient Visit (Including Example Questions)

• Items to prepare
  • A list of currently used medications (including prescriptions, OTC medications, and supplements)
  • Medical history (heart disease, autoimmune disease, allergies, and recent infections)
  • Copies of recent test results (electrocardiogram, echocardiogram, blood test results, CMR, myocardial biopsy results, etc.)
  • Record of symptom changes: onset, frequency, and type of symptoms (chest pain, syncope, shortness of breath, palpitations, etc.), and whether they improve or worsen with exercise
  • Whether syncope or severe dizziness has occurred, and any history of emergency treatment at a hospital
• Information to provide to the doctor during the outpatient visit (example questions)
  • "I brought my recent electrocardiogram and echocardiogram results. Have there been any changes?"
  • "Could any of the medications I am currently taking affect my heart condition?"

Examples of General Questions to Ask the Doctor

• "What are the main side effects of this medication (or these medications), and what symptoms should I watch for?"
• "How much recovery of my current cardiac function can be expected (prognosis)?"
• "What activities or lifestyle habits should I avoid in daily life?"
• "How often should I undergo follow-up tests (electrocardiogram, echocardiogram, CMR)?"

Examples of Disease-Specific Questions

• "Was the presence or absence of a virus confirmed in the biopsy (myocardial biopsy) results, and do I need to use immunosuppressants based on those results?"
• "If my ventricular ejection fraction does not recover, when should ICD (defibrillator) implantation be considered?"

Follow-up and prognosis summary: In general, 40–60% of patients make a complete recovery after the acute phase, but approximately 20% may progress to dilated cardiomyopathy within several years. Even after recovery of cardiac function, maintaining heart failure medications for at least 6 months and then undergoing annual electrocardiographic and echocardiographic follow-up for the subsequent 4 years are recommended.