Myocarditis

Aka: Myocarditis, Viral Myocarditis, Postinfectious Myocarditis, Dilated Cardiomyopathy Secondary to Viral Myocarditis, Viral Carditis

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II. Epidemiology

  1. Ages
    1. Children: Age <2 years old
    2. Adolescents: Age 14 to 18 years old
    3. Adults: Ages 20 to 40 years old

III. Causes

  1. See Secondary Cardiomyopathy (includes Viral Myocarditis Causes)

IV. Associated Conditions

  1. Pericarditis

V. Precautions

  1. Myocarditis is a clinical diagnosis with no single, definitive noninvasive diagnostic test
  2. Exercise a high level of suspicion in atypical presentations of common acute cardiopulmonary diseases

VI. Symptoms

  1. Presentations vary widely
    1. Most cases are mild and asymptomatic
    2. However, can be severe and life-threatening (especially in children)
      1. May be responsible for up to 20% of unexplained cardiac death in young adults
  2. Influenza-like illness presentation is common
    1. Fever (Viral Myocarditis)
    2. Fatigue
    3. Myalgias
    4. Arthralgias
    5. Malaise
  3. Chest symptoms
    1. Palpitations
    2. Pleuritic Chest Pain
    3. Sinus Tachycardia out of proportion to other findings (or other Dysrhythmia)
    4. Dyspnea on exertion
    5. Heart Block (Lyme Disease, Sarcoidosis, giant cell Myocarditis)
      1. Bradycardia
      2. Syncope
  4. Symptoms related to secondary events and decompensation
    1. Myocardial Infarction
    2. Acute Dysrhythmia
    3. Congestive Heart Failure or Cardiogenic Shock
  5. Infant and young child presentation
    1. Poor feeding
    2. Lethargy
    3. Respiratory distress (Tachypnea, intercostal retractions, grunting)
    4. Gastrointestinal Symptoms (Nausea, Vomiting or Abdominal Pain)

VII. Signs

  1. Pericardial Friction Rub
  2. Loud S3 Gallop
  3. Sinus Tachycardia (or other fast Dysrhythmia)
    1. Out of proportion to other causes (e.g. beyond what would be expected with fever alone)
  4. Weak pulses

VIII. Labs

  1. Complete Blood Count
    1. Leukocytosis
  2. Troponin I increased
    1. Very high Troponins may be seen in Myocarditis (higher than in Acute Coronary Syndrome)
    2. Often normal, especially in children
  3. Brain Natriuretic Peptide (BNP, ntBNP) increased
  4. Thyroid Stimulating Hormone (TSH)
  5. Lactic Acid
  6. Venous Blood Gas (VBG)
  7. Serum Aspartate Aminotransferase
    1. Nonspecific increase is also seen with Kawasaki Disease
  8. Acute phase reactants
    1. Erythrocyte Sedimentation Rate (ESR) >60 mm/h
    2. C-Reactive Protein (CRP) increased

IX. Diagnostics: Electrocardiogram

  1. Sinus Tachycardia
  2. QRS abnormality (associated with worse prognosis)
    1. Low-voltage QRS Complexes
    2. Wide QRS Complex
    3. Pathologic Q Waves
  3. Diffuse EKG changes (all leads)
  4. Saddle-shaped ST Segment Elevation progresses to T Wave Inversion
  5. EKG normalizes in 2 months
  6. Conduction abnormalities may occur
    1. Heart Block including complete Heart Block (Lyme Disease, Sarcoidosis, giant cell Myocarditis)

X. Imaging

  1. Chest XRay
    1. Cardiomegaly in 50% cases
    2. Pulmonary vascular congestion
    3. Pleural Effusions
  2. Echocardiogram
    1. Dilated Cardiomyopathy
    2. Left Ventricular Dilation
    3. Decreased ejection fraction
  3. Cardiac MRI
    1. Most accurate non-invasive imaging modality to diagnose Myocarditis
    2. Assess LV Ejection fraction, wall thickness, ventricle size, tissue injury
  4. Endomyocardial Biopsy Indications
    1. Fulminant myocardititis
    2. Acute Dilated Cardiomyopathy with VT or complete Heart Block refractory to standard management

XI. Differential Diagnosis

  1. See Congestive Heart Failure
  2. See Acute Coronary Syndrome
  3. Pneumonia
  4. Asthma
  5. Sepsis

XII. Management

  1. Management is typically symptomatic
    1. Chest Pain
      1. Aspirin
      2. NSAIDS
        1. Contraindicated in shock, Heart Failure, renal Impairment or injury, Anticoagulant or antiplatelet use
      3. Colchicine 0.6 mg orally twice daily (once daily if weight <70 kg)
        1. Indicated in concurrent Pericarditis
    2. Monitoring
      1. Hypotension
      2. Arrhythmias
  2. Severe, Fulminant Myocarditis requires Critical Care
    1. Hypotension
    2. Severe Congestive Heart Failure
    3. Cardiogenic Shock
    4. Complete Heart Block
  3. Specific management may be based on underlying cause
    1. Lyme Disease
    2. Mycobacterium tuberculosis
    3. Trypanosoma cruzi
    4. Influenza Myocarditis
      1. Oseltamavir (Tamiflu) started at time of diagnosis (even if >2-3 days from onset)
    5. Giant cell Myocarditis
      1. Corticosteroids (as below) AND
      2. Immunosuppressants (e.g. Tacrolimus, Cyclosporine)
  4. Corticosteroids
    1. Indications
      1. Autoimmune causes (e.g. Eosinophilic Myocarditis, sarcoiditis)
      2. Immune Checkpoint Inhibitor induced Myocarditis
    2. Protocol
      1. Methylprednisolone 7-14 mg/kg/dose IV daily for 3 days, THEN
      2. Prednisone 1 mg/kg/dose and tapered over months
    3. Adjunctive medications
      1. Pneumocystis Prophylaxis
  5. Immunoglobulin Indications
    1. Autoimmune causes
    2. Inflammatory causes (e.g. Rheumatoid Arthritis, Systemic Lupus Erythematosus)
  6. Disposition is based on severity of clinical presentation
    1. Initial inpatient management is waranted in severe cases
    2. Most acute Myocarditis in young children are admitted, often to Intensive Care unit
  7. Young children may present in severe CHF, and require intensive management
    1. Endotracheal Intubation
    2. Inotropic support (Dopamine, Dobutamine, Milrinone)
    3. Consider Diuretics (Furosemide) if hypertensive and Fluid Overload
    4. Afterload reduction
    5. Dysrhythmia management (e.g. Amiodarone, Lidocaine)
    6. Transfer to pediatric Intensive Care with ECMO capability
  8. Various agents have been used historically, especially for Viral Myocarditis (e.g. coxsachievirus)
    1. IV Ig (effective in Kawasaki's Disease, but not in Viral Myocarditis)
      1. Robinson (2015) Cochrane Database Syst Rev (5): CD004370 [PubMed]
    2. Immunosuppresants (Corticosteroids, Cyclosporine) have not been effective in Viral Myocarditis
      1. Chen (2013) Cochrane Database Syst Rev (1):CD004471 [PubMed]

XIII. Complications

  1. Syncope
  2. Cardiac Tamponade
  3. Congestive Heart Failure
  4. Sudden Cardiac Death (Dysrhythmia associated)
    1. Highest risk in age <5 years old

XIV. References

  1. (2025) Presc Lett 32(8): 47
  2. Claudius, Behar, Salway and Kearl in Herbert (2018) EM:Rap 18(5): 1-3
  3. DeMeester and Weinstock in Swadron (2022) EM:Rap 22(5): 15-7
  4. Sharrief in Herbert (2012) EM:Rap 12(5): 8
  5. Klauer (2013) Congestive Heart Failure and Myocarditis, EM Bootcamp, CEME
  6. Pacheco and Rawani-Patel (2019) Crit Dec Emerg Med 33(5): 3-11
  7. Kong (2024) JMIR Public Health Surveill 10:e46635 +PMID: 38206659 [PubMed]

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