Overview
Myocarditis
Topic Overview
Summary
Myocarditis is inflammation of the myocardium, most commonly caused by viral infection. It presents with chest pain, heart failure, or arrhythmias, often following a viral prodrome. ECG may mimic STEMI. Diagnosis is confirmed by cardiac MRI. Treatment is supportive (heart failure management, arrhythmia treatment). Most cases resolve, but some progress to dilated cardiomyopathy. Fulminant myocarditis can cause cardiogenic shock requiring mechanical support.
Key Facts
- Cause: Viral (most common — Coxsackie B, adenovirus, parvovirus B19); autoimmune; drug-induced
- Presentation: Chest pain + heart failure + arrhythmia, often after viral illness
- ECG: May mimic STEMI (diffuse ST elevation, without reciprocal changes)
- Diagnosis: Cardiac MRI (Lake Louise criteria); consider endomyocardial biopsy
- Treatment: Supportive — heart failure therapy, arrhythmia management
- Prognosis: Most recover; some progress to dilated cardiomyopathy
Clinical Pearls
Young patient with chest pain + elevated troponin + recent viral illness = think myocarditis, not just MI
ECG in myocarditis can mimic STEMI — diffuse ST elevation without reciprocal changes
Cardiac MRI is the gold standard non-invasive test — shows oedema and late gadolinium enhancement
Why This Matters Clinically
Myocarditis can mimic MI and cause sudden death. It is a common cause of sudden cardiac death in young athletes. Early recognition and appropriate management prevent unnecessary interventions and identify those at risk of deterioration.
Visual Summary
Visual assets to be added:
- ECG showing diffuse ST elevation
- Cardiac MRI showing myocardial oedema and LGE
- Myocarditis aetiology diagram
- Management algorithm
Epidemiology
Incidence
- Estimated 10-22 per 100,000/year (likely underdiagnosed)
- Common cause of sudden cardiac death in young people
Demographics
- All ages; peak in young adults (20-40 years)
- Male predominance (60-70%)
Causes
| Category | Examples |
|---|---|
| Viral | Coxsackie B, adenovirus, parvovirus B19, influenza, COVID-19 |
| Autoimmune | Systemic lupus, sarcoidosis, giant cell myocarditis |
| Drug-induced | Immune checkpoint inhibitors, clozapine, cocaine |
| Toxic | Alcohol, doxorubicin |
| Other | Parasitic (Chagas), bacterial (diphtheria, Lyme) |
Pathophysiology
Mechanism
- Viral infection of myocytes (direct cytopathic effect)
- Immune response → inflammation, myocyte necrosis
- May progress to:
- Resolution and recovery
- Chronic inflammation → dilated cardiomyopathy
- Fulminant myocarditis → cardiogenic shock
Histopathology (Dallas Criteria)
- Inflammatory infiltrate + myocyte necrosis
- Lymphocytic infiltrate most common
Why It Can Mimic MI
- Focal inflammation → localised ECG changes, troponin rise
- May cause regional wall motion abnormalities
Clinical Presentation
Symptoms
Signs
Presentations
| Type | Features |
|---|---|
| Mild | Symptoms only; normal LV function |
| Acute heart failure | Dyspnoea, oedema, reduced EF |
| Arrhythmic | VT, VF, heart block, sudden death |
| Fulminant | Cardiogenic shock; may need mechanical support |
Red Flags
| Finding | Significance |
|---|---|
| Cardiogenic shock | Fulminant myocarditis — ICU |
| VT/VF | High risk of sudden death |
| Severely reduced EF | Poor prognosis |
Chest pain (often pleuritic or positional)
Common presentation.
Dyspnoea
Common presentation.
Palpitations
Common presentation.
Fatigue
Common presentation.
Viral prodrome (fever, myalgia, respiratory or GI symptoms) — 50-80%
Common presentation.
Clinical Examination
Vital Signs
- Tachycardia
- Hypotension (if cardiogenic shock)
- Fever (may be present)
Cardiovascular
- S3 gallop
- Signs of heart failure
- Pericardial rub (myopericarditis)
Respiratory
- Crackles (pulmonary oedema)
Investigations
Blood Tests
| Test | Finding |
|---|---|
| Troponin | Elevated (confirms myocardial injury) |
| BNP/NT-proBNP | Elevated if heart failure |
| CRP, ESR | Elevated (inflammation) |
| FBC | May show eosinophilia (eosinophilic myocarditis) |
| Viral serology | May identify cause (often not clinically useful) |
ECG
| Finding | Notes |
|---|---|
| Diffuse ST elevation | Without reciprocal changes (unlike STEMI) |
| PR depression | Suggests pericardial involvement |
| Arrhythmias | VT, VF, heart block |
| Low voltage | If pericardial effusion |
Echocardiography
- LV function (may be normal or reduced)
- Regional wall motion abnormalities
- Pericardial effusion
Cardiac MRI — Gold Standard Non-Invasive
| Finding | Significance |
|---|---|
| Myocardial oedema (T2) | Active inflammation |
| Late gadolinium enhancement (LGE) | Fibrosis/scarring |
| Lake Louise criteria | Diagnostic |
Endomyocardial Biopsy
- Not routine; consider if:
- Fulminant myocarditis
- Suspected giant cell or eosinophilic myocarditis
- Uncertain diagnosis
Coronary Angiography
- If STEMI cannot be excluded clinically
- Often normal in myocarditis
Classification & Staging
By Clinical Presentation
| Type | Features |
|---|---|
| Subclinical | Incidental finding |
| Acute | Symptoms under 30 days |
| Chronic | Symptoms over 30 days |
| Fulminant | Rapid onset, cardiogenic shock |
By Aetiology
- Viral
- Autoimmune
- Drug-induced
- Idiopathic
Management
Supportive Care — Mainstay
Heart Failure Management:
- ACE inhibitor or ARB
- Beta-blocker (once stable)
- Diuretics (if fluid overloaded)
Arrhythmia Management:
- Anti-arrhythmics if needed
- ICD consideration if sustained VT/VF or severely reduced EF
Activity Restriction:
- Avoid strenuous exercise for 3-6 months (risk of sudden death)
Fulminant Myocarditis — ICU
| Intervention | Details |
|---|---|
| Inotropes | Dobutamine, milrinone |
| Mechanical circulatory support | VA-ECMO, LVAD as bridge |
| Heart transplant | If refractory |
Immunosuppression
- Not routine
- Consider in giant cell myocarditis (steroids, cyclosporine)
- Eosinophilic myocarditis (steroids)
Treat Underlying Cause
- Stop causative drugs
- Treat autoimmune disease
Complications
Acute
- Cardiogenic shock
- Arrhythmias (VT, VF, heart block)
- Sudden cardiac death
- Thromboembolic events
Chronic
- Dilated cardiomyopathy
- Chronic heart failure
- Recurrent myocarditis
Prognosis & Outcomes
Prognosis
- Most recover fully (50-70%)
- 10-20% progress to dilated cardiomyopathy
- Fulminant myocarditis paradoxically has better long-term prognosis (if survive acute phase)
Mortality
- Overall low (under 5%)
- Higher in fulminant myocarditis, giant cell myocarditis
Return to Exercise
- Avoid competitive sport for 3-6 months
- Repeat echo and cardiac MRI before return
Evidence & Guidelines
Key Guidelines
- ESC Position Statement on Myocarditis (2013)
- AHA Scientific Statement on Myocarditis
Key Evidence
- Cardiac MRI is the non-invasive gold standard
- Immunosuppression only for specific subtypes (giant cell, eosinophilic)
Patient & Family Information
What is Myocarditis?
Myocarditis is inflammation of the heart muscle. It is often caused by a viral infection and can cause chest pain, tiredness, and heart problems.
Symptoms
- Chest pain
- Shortness of breath
- Feeling very tired
- Palpitations
Treatment
- Rest and avoiding exercise
- Medication to support the heart
- Most people recover fully
What Happens Next?
- You will need follow-up scans
- Avoid strenuous exercise for several months
Resources
References
Primary Guidelines
- Caforio AL, et al. Current state of knowledge on aetiology, diagnosis, management, and therapy of myocarditis: a position statement of the ESC Working Group on Myocardial and Pericardial Diseases. Eur Heart J. 2013;34(33):2636-2648. PMID: 23824828
Key Studies
- Ammirati E, et al. Clinical presentation and outcome in a contemporary cohort of patients with acute myocarditis. Circulation. 2018;138(11):1088-1099. PMID: 29764898
- Ferreira VM, et al. Cardiovascular magnetic resonance in nonischemic myocardial inflammation: expert recommendations. J Am Coll Cardiol. 2018;72(24):3158-3176. PMID: 30545455