Pediatric Myocarditis

Three presentations organize the differential

Age changes the disguise

Find the mismatch

• Tachycardia is greater or more persistent than fever, pain, dehydration, or distress explains.
• Respiratory distress coexists with hepatomegaly, gallop, cool extremities, delayed capillary refill, weak pulses, or oliguria.
• Chest radiograph suggests cardiomegaly or pulmonary edema rather than focal air-space disease.
• The child worsens after fluid, cannot tolerate feeds, or has recurrent “sepsis” without a coherent infectious source.
• New AV block, ventricular arrhythmia, syncope, or diffuse ST-T abnormality accompanies systemic illness.

Order a purpose-built initial evaluation

Use CMR correctly

CMR assesses function, edema, nonischemic injury, scar, and pericardial involvement. Obtain it when the patient is stable enough, the result will change diagnostic confidence or follow-up, and a pediatric-quality study is feasible.

A negative or technically limited early CMR does not overrule a compelling clinical phenotype. Timing, scanner, protocol, age, sedation, and disease distribution matter.

Reserve EMB for questions tissue can answer

EMB remains the pathologic reference but has procedural risk and sampling limitations. It is not required in every stable, clinically suspected case.

• Consider when fulminant or refractory disease raises a treatable histologic diagnosis: giant cell, eosinophilic/hypersensitivity, sarcoid, immune-mediated, or unusual infection.
• Consider with unexplained severe HF, malignant arrhythmia, or high-grade AV block when the result may change therapy.
• Coordinate histology, immunohistochemistry, and molecular pathogen testing; a random “viral culture” is not an adequate biopsy strategy.
• Do not delay stabilization, transfer, or MCS to obtain tissue.

Keep mimics active until they are excluded

Fluids and diuresis: do not treat the number alone

• Congested: avoid routine bolus; use IV loop diuretic if blood pressure/perfusion permit and reassess response.
• Uncertain preload: bedside echo and repeated examination are more valuable than assumptions.
• True hypovolemia: use a small cautious aliquot with immediate reassessment rather than an automatic large rapid bolus.
• Track urine output, weight, renal function, electrolytes, hepatomegaly, work of breathing, lactate, and perfusion.

Vasoactive therapy follows phenotype

Specialist directed No single inotrope is universally “preferred.” Choice depends on BP, SVR, rhythm, kidney function, and ventricular phenotype.

Ventilation is therapy—and a hemodynamic event

• Reduce work of breathing and correct hypoxemia/acidosis; noninvasive support may help selected cooperative patients.
• Positive pressure can reduce LV afterload but can also impair venous return and precipitate collapse in marginal circulation.
• If intubation is required, involve cardiac anesthesia/critical care when possible, prepare vasoactive rescue, use hemodynamically appropriate induction, and have an MCS contingency.
• Do not delay a necessary airway; make the airway plan proportional to cardiovascular risk.

Electrical instability uses PALS principles plus myocardial context

• Unstable tachyarrhythmia with a pulse: synchronized cardioversion; pulseless VT/VF: defibrillation and high-quality CPR.
• Bradycardia/high-grade AV block with poor perfusion: oxygenation/ventilation, appropriate medications, and pacing; electrophysiology input early.
• Correct hypoxemia, acidosis, electrolytes, fever, pain, and catecholamine excess.
• Antiarrhythmic choice is rhythm- and hemodynamic-specific; avoid declaring lidocaine or amiodarone universally superior.
• Recurrent malignant arrhythmia may be a sign that circulation needs mechanical support, not merely another drug.

Call MCS before irreversible injury

Myocarditis has meaningful recovery potential when perfusion is supported through the inflammatory insult. Consider advanced support for worsening lactate/acidosis, end-organ injury, refractory hypotension, escalating vasoactives, severe biventricular dysfunction, recurrent arrest, or uncontrollable arrhythmia.

Antithrombotic therapy is individualized

• Therapeutic anticoagulation is indicated for documented intracardiac thrombus and is protocolized during ECMO/VAD.
• Severe LV dysfunction, marked dilation, spontaneous echo contrast, central lines, immobility, and other VTE risks may prompt prophylaxis.
• No evidence-based universal rule says every child with LVEF below a fixed threshold should receive aspirin until LVEF exceeds 40%.
• Choose agent and intensity with cardiology/hematology/MCS teams, balancing bleeding, procedures, renal function, and thrombosis risk.

What nearly every child needs

• Appropriate monitored setting, serial hemodynamic and rhythm assessment, and cardiology involvement.
• Cause-appropriate supportive care: decongestion, perfusion support, ventilation, arrhythmia treatment, and nutrition.
• Evaluation for dangerous mimics and specific treatable etiologies.
• Early advanced-HF/MCS pathway for high-risk or worsening disease.
• A discharge plan with medication reconciliation, follow-up testing, activity limits, warning symptoms, and a reachable team.

IVIG and corticosteroids: common does not mean proven

Specific etiologies can change treatment

Detection of a respiratory virus alone does not establish causality or justify a myocarditis-specific antiviral regimen.

Transition to chronic HF care only after stabilization

• Once perfusion and volume status are stable, introduce age- and phenotype-appropriate chronic HF therapy with pediatric cardiology.
• ACE inhibitor/ARB/ARNI, beta-blocker, mineralocorticoid antagonist, and other therapies depend on age, renal function, BP, rhythm, and evidence; pediatric data vary.
• Avoid starting or escalating beta-blockade during active decompensation or shock.
• Digoxin is not a routine acute-myocarditis treatment; if considered later, risk, rhythm, renal function, and narrow therapeutic index require specialist ownership.
• Persistent or recurrent disease should prompt reassessment for genetic cardiomyopathy and alternative inflammatory etiologies.

The 2023 AHA pediatric cardiomyopathy statement is the appropriate companion for ongoing ventricular dysfunction.6

Return to activity is no longer one fixed clock

During active myocarditis, avoid vigorous exercise and competitive sport. Reassessment must demonstrate clinical recovery and acceptable arrhythmic risk; the timeline depends on the initial phenotype.

Follow-up closes the hidden-risk gap

• Confirm cardiology follow-up before discharge; timing depends on ventricular function, rhythm, biomarkers, CMR, and trajectory.
• Repeat ECG, echocardiography, biomarkers, ambulatory monitoring, exercise testing, and/or CMR according to phenotype—not a generic calendar.
• Escalate recurrent chest pain, syncope, palpitations, dyspnea, exercise intolerance, edema, poor feeding, or fever with cardiovascular signs.
• Address school/activity documentation, medication adherence, CPR/AED planning when relevant, and the psychological burden of sudden restriction/critical illness.
• Do not call normalized LVEF synonymous with complete risk resolution; residual scar or arrhythmia may alter surveillance.