Pediatric Myocarditis¶

Learning Objectives¶

Core Knowledge & Clinical Reasoning¶

[ ] Apply diagnostic certainty strata (suspected, probable, definite) using clinical, laboratory, and imaging findings
[ ] Interpret cardiac MRI using Lake Louise criteria (edema, hyperemia, necrosis/fibrosis)
[ ] Differentiate fulminant from acute myocarditis and adjust management accordingly
[ ] Evaluate indications for endomyocardial biopsy in atypical or refractory cases

Acute Management¶

[ ] Formulate acute management plan including hemodynamic support and arrhythmia monitoring
[ ] Determine when to escalate to mechanical circulatory support (ECMO, VAD)

Communication & Counseling¶

[ ] Counsel families on prognosis, expected recovery timeline, and potential for chronic cardiomyopathy
[ ] Discuss return-to-play criteria and restrictions with patients and families (minimum 3-6 months)

Systems-Based Practice¶

[ ] Coordinate follow-up surveillance including serial echo, Holter, and exercise testing before activity clearance
[ ] Ensure appropriate school accommodations during recovery period

Key Guidelines¶

2021 AHA Scientific Statement: Diagnosis and Management of Myocarditis in Children Circulation. 2021;144:e123-e135

2025 ESC Guidelines on Inflammatory Myocardial and Pericardial Syndromes European Heart Journal. 2025

Diagnostic Certainty Strata¶

Level	Definition
Biopsy-proven	Histopathologic confirmation (Dallas criteria)
Clinically suspected, CMR-confirmed	Lake Louise criteria positive
Clinically suspected	Clinical presentation + supportive findings
Possible myocarditis	Some features, diagnosis uncertain

Etiology¶

Viral (Most Common)¶

Enteroviruses (coxsackievirus)
Adenovirus
Parvovirus B19
Human herpesvirus 6
SARS-CoV-2
Influenza

Other Causes¶

Autoimmune (giant cell, eosinophilic)
Drug-induced (checkpoint inhibitors)
Toxic
Idiopathic

Clinical Presentation¶

Spectrum¶

Fulminant: Rapid hemodynamic deterioration
Acute: Typical presentation over days-weeks
Chronic active: Ongoing inflammation
Chronic persistent: Low-grade, may cause DCM

Common Symptoms¶

Chest pain
Heart failure symptoms
Palpitations/arrhythmias
Preceding viral illness

Diagnostic Evaluation¶

ECG¶

Abnormalities in ~90% of cases
ST-T changes
Low voltages
Arrhythmias (PVCs, VT)
Heart block

Biomarkers¶

Troponin: Elevated but NOT universally present
BNP/NT-proBNP: Correlates with LV dysfunction
CRP/ESR: Nonspecific inflammation

Echocardiography¶

LV dysfunction (global or regional)
Pericardial effusion
Chamber dilation
Valvular regurgitation

Cardiac MRI¶

Now cornerstone for noninvasive diagnosis

Lake Louise Criteria (Updated 2018): - T2-based criteria: Myocardial edema (T2 mapping, T2-weighted imaging) - T1-based criteria: Non-ischemic injury (LGE, T1 mapping, ECV)

Positive = ≥1 T2 criterion + ≥1 T1 criterion

Endomyocardial Biopsy¶

Indications: - New-onset HF with hemodynamic compromise - Suspected giant cell myocarditis - Failure to respond to treatment - Arrhythmias with suspected cardiac involvement

Management¶

Supportive Care (Primary Therapy)¶

Similar to acute heart failure management
Diuretics for congestion
Avoid NSAIDs (animal data suggests harm)

Inotropic Support¶

Milrinone: First-line for inotropy
Avoids catecholamine excess
Dobutamine as alternative

Mechanical Circulatory Support¶

Early consideration for high-risk patients
ECMO for fulminant myocarditis
VAD as bridge to recovery or transplant

Immunomodulation¶

IVIG: Limited evidence; center-specific protocols
Corticosteroids: Limited evidence; may be harmful if viral etiology
Reserve for suspected autoimmune or giant cell

Activity Restriction¶

Minimum 3-6 months of exercise restriction
Critical for preventing SCD during healing

Return to Activity Criteria¶

ALL must be met: 1. Normal LV function by echocardiography 2. No arrhythmias on Holter monitoring 3. No arrhythmias during exercise stress testing 4. Normal/improving biomarkers 5. CMR shows resolved inflammation (if repeated) 6. ≥3-6 months from acute illness

Prognosis¶

~60-80% recover completely
~10-20% develop chronic DCM
~10% require transplant or die
Fulminant myocarditis: Paradoxically better long-term prognosis if survive acute phase

Board Pearls¶

Pearl: CMR is cornerstone for noninvasive diagnosis

Lake Louise criteria: T2 (edema) + T1 (injury) findings

Pearl: Milrinone is first-line inotrope

Avoids catecholamine toxicity in inflamed myocardium

Pearl: Return-to-play: 3-6 months minimum

Requires normal echo, Holter, AND exercise stress test

Self-Assessment¶

Q1: A 14-year-old presents with chest pain and dyspnea 1 week after a viral URI. ECG shows diffuse ST elevations. Troponin is mildly elevated. Echo shows EF of 48%. What is the next best diagnostic test?

Answer

**Answer**: Cardiac MRI **Rationale**: This presentation is consistent with clinically suspected myocarditis. CMR with Lake Louise criteria is now the cornerstone for noninvasive diagnosis. It can demonstrate myocardial edema (T2) and injury (T1/LGE), confirming the diagnosis and assessing severity.

Q2: A 12-year-old had biopsy-proven myocarditis 2 months ago. EF normalized to 58%. He wants to return to soccer. Is he cleared?