OVERVIEW

What is pediatric myocarditis?

Pediatric myocarditis is a common heart disease in children, characterized by inflammation, damage, necrosis, and edema of the heart caused by various infections, certain diseases, or medications.

What causes pediatric myocarditis?

Infection is a common cause, with viral infections being the most frequent.

What are the common symptoms of pediatric myocarditis?

Common symptoms of pediatric myocarditis include fatigue, excessive sweating, irritability, chest tightness, and chest pain.

How is pediatric myocarditis treated?

Treatment mainly involves rest, anti-infection measures, and active management of complications such as arrhythmias and heart failure.

Is pediatric myocarditis serious?

The severity of pediatric myocarditis varies depending on the extent and severity of myocardial damage. Severe cases may lead to acute heart failure (reduced heart pumping function), arrhythmias (irregular heartbeat), or even death. Mild cases may show no obvious symptoms but carry the risk of progressing to chronic myocarditis or dilated cardiomyopathy if not promptly recognized and treated.

Can pediatric myocarditis be cured?

Most pediatric myocarditis patients with timely diagnosis and active treatment can fully recover, while a few cases progress rapidly and have poor survival outcomes.

SYMPTOMS

What are the common manifestations of pediatric myocarditis?

Affected children often first exhibit signs of infection, such as fever, sore throat, cough, vomiting, diarrhea, and muscle pain. Most develop myocarditis symptoms 1–3 weeks after viral infection.

What types of pediatric myocarditis exist?

Based on clinical presentation, it can be classified into:

• Asymptomatic type: ECG shows S-T segment changes 1–4 weeks post-infection, but the child shows no obvious symptoms.

• Arrhythmia type: Various types of arrhythmias may occur, sometimes multiple simultaneously.

• Heart failure type: Presents as heart failure. Mild cases show fatigue, palpitations, chest tightness, and poor appetite, while severe cases may involve dyspnea and cyanosis (bluish skin/mucous membranes).

• Fulminant type: Symptoms resemble myocardial infarction, including chest pain and tightness, with markedly elevated cardiac biomarkers. Note: Fulminant myocarditis has a high mortality rate and is easily missed, so immediate medical attention is crucial.

• Sudden death type: The child dies abruptly without prior specific symptoms.

What are the stages of pediatric myocarditis?

• Acute phase: Lasts ≤6 months with variable symptoms. Mild cases primarily involve fatigue, possibly with weakness, sweating, lethargy, palpitations, chest tightness, or dizziness. Severe cases may show pallor, cyanosis, dyspnea, syncope, or sudden death.

• Prolonged phase: Persists >6 months. Symptoms recur, ECG abnormalities persist without improvement, and elevated cardiac biomarkers indicate ongoing myocardial necrosis.

• Chronic phase: Lasts ≥1 year. Progressive cardiac enlargement and declining function, with recurrent heart failure and arrhythmias. Some cases progress insidiously to chronicity before detection, while others result from delayed/inadequate treatment. Prognosis is poor, often leading to death from infection, arrhythmias, or heart failure.

What severe complications can pediatric myocarditis cause?

Pediatric myocarditis may lead to myocardial inflammation, necrosis, life-threatening arrhythmias, or progression to cardiomyopathy if unresolved. Rarely, sudden death may occur.

CAUSES

What are the causes of pediatric myocarditis?

• Infection: Pathogens that can cause myocarditis include viruses, bacteria, atypical pathogens, fungi, or parasites, with viral infections being the most common. Common viruses include adenovirus, enterovirus (including coxsackievirus, echovirus, and poliovirus), herpesvirus, cytomegalovirus, rubella virus, etc.

• Diseases: Certain autoimmune diseases, endocrine and metabolic disorders, genetic defects, and tumors can cause myocardial damage, leading to myocarditis.

• Medications: Drugs such as doxorubicin, anthracycline chemotherapy agents, cyclophosphamide, catecholamines, emetine, and antimony compounds can induce myocarditis.

Is pediatric myocarditis contagious?

Pediatric myocarditis itself is not contagious, but the viruses, bacteria, or other pathogens that cause it can be transmitted. Other children infected with these pathogens may not necessarily develop myocarditis.

DIAGNOSIS

What tests are needed for pediatric myocarditis?

• Electrocardiogram (ECG) or Holter monitoring: To identify arrhythmias or ST-T changes. Significant ECG abnormalities include: ST-T changes persisting for more than 4 days with dynamic variations in two or more major leads dominated by R waves; newly detected sinoatrial or atrioventricular block, complete right or left bundle branch block, sinus arrest, polymorphic or multifocal premature beats, non-av nodal or atrioventricular reentrant ectopic tachycardia, atrial flutter, atrial fibrillation, ventricular flutter, ventricular fibrillation, low QRS voltage, abnormal Q waves, etc.

• Cardiac biomarker testing: To detect active myocardial cell injury or necrosis. Elevated troponin T or I or serum creatine kinase-MB.

• Cardiac magnetic resonance imaging (MRI): Typical findings of myocardial inflammation must include at least two of the following:

• T2-weighted imaging showing high signal intensity, indicating myocardial edema;

• T1-weighted imaging showing early gadolinium enhancement, indicating myocardial hyperemia and capillary leakage;

• T1-weighted imaging showing at least one non-ischemic regional late gadolinium enhancement, indicating myocardial necrosis and fibrosis.

• Etiological testing: Viral isolation or detection of viral nucleic acid via nucleic acid probes in endocardial, myocardial, or pericardial tissue or pericardial effusion confirms the diagnosis.

• Myocardial biopsy: At least three sampling sites are required for endomyocardial biopsy. A positive result confirms the diagnosis, but a negative result does not rule it out.

How is pediatric myocarditis diagnosed?

The diagnosis is based on clinical manifestations, combined with cardiac enlargement and ECG changes, with confirmation relying on etiological testing.

• Upper respiratory or gastrointestinal viral infection typically occurs 1–3 weeks before the onset of myocarditis.

• Children may present with chest tightness, chest pain, palpitations, fatigue, dizziness, or abdominal pain, while infants may refuse feeding, appear lethargic, and exhibit pallor, cyanosis, or cold extremities.

• Clinical manifestations of heart failure or cardiogenic shock (coma due to cardiac disease).

• Imaging studies reveal cardiac enlargement.

• Elevated serum cardiac biomarkers with dynamic changes.

• Significant ECG or Holter monitoring abnormalities.

• Cardiac MRI findings consistent with typical myocarditis.

• Positive anti-myocardial antibodies.

• Viral isolation or detection of viral nucleic acid in endocardial, myocardial, or pericardial tissue.

• Endomyocardial biopsy pathology and immunohistochemistry showing ≥14 leukocytes/mm², including ≥4 monocytes/mm² and CD3+ T lymphocytes ≥7 cells/mm².

TREATMENT

Which department should a child with myocarditis visit?

They should visit the Pediatrics or Neonatology Department and the Cardiovascular Medicine Department.

How should pediatric myocarditis be treated?

• Rest: During the acute phase, bed rest for 3–4 weeks is recommended to avoid activity and reduce cardiac load.

• Medication: Use drugs that nourish the myocardium and improve myocardial metabolism, such as vitamin C, coenzyme complex, fructose-1,6-diphosphate, and phosphocreatine. For myocarditis caused by specific viral infections, antiviral therapy may be administered; bacterial myocarditis requires antibiotic treatment. Some cases of fulminant myocarditis with severe arrhythmias may require immunosuppressive therapy.

• Symptomatic treatment: Actively correct heart failure and provide antiarrhythmic treatment. This may involve digitalis drugs, vasoactive drugs, antiarrhythmic drugs, or the installation of a cardiac pacemaker.

DIET & LIFESTYLE

Can children with myocarditis exercise?

During the acute phase, bed rest is necessary; those with cardiac insufficiency should limit physical activity to avoid worsening heart failure.

During recovery, children with stable cardiac function may engage in moderate activity.

What lifestyle precautions should be taken for pediatric myocarditis?

• Ensure adequate rest and moderate activity, avoiding overexertion.

• Stay warm and avoid catching cold.

• Practice personal hygiene to prevent respiratory infections.

What dietary precautions should be taken for pediatric myocarditis?

Maintain a balanced diet and correct poor eating habits like picky or selective eating.

During illness, consume high-energy, high-protein, easily digestible foods such as rice, noodles, meat, eggs, dairy, and fish.

PREVENTION

How to Prevent Pediatric Myocarditis?

• Engage in moderate exercise regularly to strengthen physical fitness and improve personal immunity.

• Adjust children's clothing according to temperature changes to prevent colds, while also enhancing physical exercise to boost disease resistance.

• Actively treating chronic conditions such as pharyngitis, tonsillitis, and rhinitis is crucial for preventing myocarditis recurrence.

• For school-aged children, maintain a balance between work and rest, follow a regular routine, ensure adequate rest and sleep, and avoid excessive fatigue.

• In terms of diet, maintain a balanced intake, avoid overeating, reduce consumption of grilled, fried, or roasted foods, and eat more fresh vegetables and fruits. When ill, use medications with potential cardiac toxicity cautiously under medical supervision.