Cardiology > Myocarditis

Background

Myocarditis is an inflammatory disease of the myocardium (heart muscle) that can impair cardiac function through direct myocyte injury, immune-mediated damage, or both. It may present as chest pain, arrhythmias, heart failure, or cardiogenic shock, and can be self-limited or progress to dilated cardiomyopathy and heart failure. 

II) Classification/Types

By Etiology: 

• • Infectious: Viral (e.g., Coxsackie B, adenovirus, parvovirus B19, SARS-CoV-2), bacterial (e.g., Lyme disease), fungal, parasitic (e.g., Trypanosoma cruzi). 

• • Autoimmune/Inflammatory: Systemic lupus erythematosus, sarcoidosis, giant cell myocarditis. 

• • Drug-Induced/Hypersensitivity: Chemotherapy (e.g., anthracyclines), checkpoint inhibitors, antibiotics, illicit drugs (e.g., cocaine). 

• • Idiopathic: No clear cause found despite thorough work-up. 

By Time Course: 

• • Acute: Rapid onset with systemic or cardiac symptoms. 

• • Chronic Active: Persistent inflammation with ongoing myocyte damage. 

• • Chronic Persistent: Persistent inflammation without ventricular dysfunction. 

• • Fulminant: Sudden, severe myocarditis with cardiogenic shock. 

By Severity: 

• • Subclinical: Detected incidentally on imaging or biopsy. 

• • Mild to Moderate: Chest pain, fatigue, preserved ejection fraction. 

• • Severe: Heart failure, arrhythmias, cardiogenic shock. 

III) Pathophysiology 

Initial myocardial insult (often viral) leads to myocyte necrosis and activation of the immune system. In genetically susceptible individuals, immune responses can become dysregulated, resulting in ongoing myocardial inflammation and fibrosis. This impairs contractility and predisposes to arrhythmias and dilated cardiomyopathy. 

IV) Epidemiology

• • Sex: More common in males (testosterone may enhance immune response). 

• • Age: Often affects young adults; viral forms especially in children and adolescents. 

• • Geography: Chagas disease prevalent in Latin America; viral myocarditis globally distributed. 

• • Comorbidities: May occur in individuals with autoimmune diseases, recent viral illness, or exposure to cardiotoxic medications. 

Etiology

I) Causes

• • Viral: Coxsackie B, adenovirus, CMV, HIV, SARS-CoV-2 

• • Bacterial: Borrelia burgdorferi (Lyme), Corynebacterium diphtheriae 

• • Protozoal: Trypanosoma cruzi (Chagas), Toxoplasma gondii 

• • Autoimmune: SLE, sarcoidosis, giant cell myocarditis 

• • Drug-induced: Clozapine, checkpoint inhibitors, doxorubicin 

• • Hypersensitivity reactions 

• • Idiopathic 

II) Risk Factors

• • Recent viral illness 

• • Autoimmune diseases 

• • Immunosuppressive therapy 

• • Exposure to cardiotoxic drugs 

• • Male sex 

• • Athletes undergoing intense training 

• • Travel to endemic areas (e.g., Chagas) 

Clinical Presentation

I) History (Symptoms)

• • Viral prodrome (fever, malaise, myalgia) 

• • Chest pain (may mimic acute MI) 

• • Palpitations or syncope 

• • Dyspnea, fatigue 

• • Orthopnea, PND 

• • Signs of heart failure (in advanced cases) 

• • Sudden death (due to ventricular arrhythmias) 

II) Physical Exam (Signs)

Vital Signs: 

• • Tachycardia 

• • Hypotension (if severe) 

Cardiac Exam: 

• • S3 gallop 

• • Murmurs (mitral regurgitation from papillary muscle involvement) 

• • Irregular rhythm (atrial or ventricular arrhythmias) 

Pulmonary: 

• • Rales in pulmonary congestion 

• • Signs of pulmonary edema in severe cases 

Peripheral: 

• • Jugular venous distention 

• • Peripheral edema 

• • Cool extremities (cardiogenic shock) 

Differential Diagnosis (DDx)

• • Acute coronary syndrome 

• • Pericarditis 

• • Heart failure (HFrEF, HFpEF) 

• • Dilated cardiomyopathy 

• • Sepsis-induced cardiomyopathy 

• • Pulmonary embolism 

• • Takotsubo cardiomyopathy 

• • Sarcoidosis 

• • Arrhythmogenic right ventricular cardiomyopathy 

Diagnostic Tests

Initial Tests: 

• • ECG: ST changes, T wave inversion, AV block, ventricular arrhythmias 

• • Troponins: Elevated (due to myocyte injury) 

• • BNP/NT-proBNP: Elevated in heart failure 

• • Chest X-ray: Cardiomegaly, pulmonary congestion 

• • Echocardiogram: Global or regional wall motion abnormalities, reduced EF, pericardial effusion 

Advanced Imaging: 

• • Cardiac MRI: Gold standard noninvasive test; shows myocardial edema, hyperemia, and late gadolinium enhancement 

• • Endomyocardial biopsy: Reserved for fulminant cases or unclear diagnosis; confirms histologic subtypes (e.g., giant cell, eosinophilic) 

• • Viral serologies or PCR: In selected cases to identify causative agent 

Treatment

I) Medical Management

Supportive Care: 

• • Rest and avoid intense physical activity 

• • Treat arrhythmias (beta-blockers, antiarrhythmics as needed) 

• • ACE inhibitors, ARBs, beta-blockers, and diuretics for heart failure symptoms 

• • IV inotropes (e.g., milrinone, dobutamine) in cardiogenic shock 

Specific Therapies (in selected cases): 

• • Immunosuppressive therapy (e.g., corticosteroids, IVIG) in autoimmune or giant cell myocarditis 

• • Antiviral therapy (unproven benefit in most viral cases) 

• • Antimicrobials for bacterial myocarditis 

II) Advanced Interventions

• • Mechanical Circulatory Support: IABP, ECMO in refractory shock 

• • Heart Transplantation: For end-stage myocarditis with irreversible heart failure 

 Patient Education, Screening, Vaccines

• • Emphasize need for rest and gradual return to activity 

• • Avoid alcohol and recreational drugs 

• • Importance of follow-up imaging 

• • Monitor for signs of heart failure (e.g., weight gain, edema, dyspnea) 

• • Vaccinations: 

• • Influenza 

• • COVID-19 

• • Pneumococcal (if immunosuppressed) 

Consults

• • Cardiology: All suspected myocarditis, especially with arrhythmias or LV dysfunction 

• • Infectious Disease: If infectious cause suspected or immunosuppressed host 

• • Electrophysiology: Recurrent or life-threatening arrhythmias 

• • Cardiothoracic Surgery: If considering biopsy or transplant 

• • Critical Care: Fulminant myocarditis requiring inotropes or MCS 

Follow-Up

• • Serial TTE: Every 1–3 months to assess LV function 

• • Cardiac MRI: To monitor resolution of inflammation 

• • ECG monitoring: For arrhythmia recurrence 

• • Return to physical activity: Typically 3–6 months post-recovery and only if LV function is normalized 

• • Lifestyle counseling: Limit alcohol, manage stress, monitor for recurrence