Myocarditis in children and adolescents:
symptoms and warning signs

Article written and reviewed by Dr Luca Moretti

Myocarditis can also occur in children, and symptoms vary greatly with age. In infants it may present with nonspecific signs such as rapid breathing, feeding difficulty, sweating during feeds, irritability or drowsiness. In older children and adolescents, chest pain, shortness of breath, palpitations, marked fatigue or a sudden decline in the ability to participate in sports are easier to recognize.
The problem is that, at first, myocarditis may resemble a common respiratory or gastrointestinal infection. Unexpected worsening, persistent tachycardia, significant breathing difficulty, fainting or signs of poor circulation require prompt assessment.

Possible signs vary with age and may include:

• rapid or difficult breathing;
• poor feeding and fatigue during feeds in younger children;
• fatigue or reduced ability to play and be physically active;
• chest pain, especially in older children;
• palpitations, dizziness or loss of consciousness;
• pallor, cold extremities or reduced responsiveness in more severe forms.

Myocarditis is inflammation of the heart muscle. In children, recognition can be more difficult because many symptoms are nonspecific and younger children cannot describe what they are feeling.

Why symptoms change with age

An adolescent can report chest pain or palpitations much like an adult. An infant, by contrast, shows the problem through behavior and breathing: the infant may eat less, frequently interrupt feeds, sweat, breathe rapidly or appear unusually tired. For this reason, the same disease can look completely different depending on age.
Presentations range from mild illness to heart failure, arrhythmias and, rarely, shock. Severity cannot be determined solely from the presence or absence of fever.

Gastrointestinal symptoms are also relatively common in children. Vomiting, abdominal pain and poor appetite may accompany myocarditis and initially suggest gastroenteritis or another infection. Suspicion increases if rapid breathing, persistent tachycardia, difficulty with exertion or other cardiac signs are also present.
A history of recent infection is common but not required and, by itself, does not establish the diagnosis.

How it can present in infants and young children

In the first years of life, symptoms can be nonspecific. An infant may have poor feeding, tire while eating, sweat more than usual or have rapid, shallow breathing. Irritability may occur or, conversely, drowsiness and reduced responsiveness. These signs can be mistaken for a common infection, especially if fever, cough, vomiting or diarrhea are present.
When the heart is struggling to pump adequately, the child may become pale, have cold hands and feet or produce less urine. The doctor may detect tachycardia, tachypnea, an enlarged liver or other signs of heart failure.

An important feature is unexpected deterioration. A child initially treated for a respiratory or gastrointestinal illness who becomes progressively more breathless, very tired or poorly responsive needs reassessment. Myocarditis is not the most common cause of these symptoms, but it is one of the conditions to consider when the course does not follow what was expected.

Symptoms in older children and adolescents

As age increases, symptoms that the child can describe directly become more common. Chest pain is an important presentation in adolescents, especially when cardiac function is preserved. Shortness of breath, palpitations, fatigue, abdominal pain, dizziness or fainting may also occur.
Another practical warning sign is reduced exercise tolerance: a young person who normally plays sports may notice that they can no longer run, climb stairs or sustain training as before.

Palpitations and syncope deserve particular attention because myocarditis can involve the electrical system of the heart. Loss of consciousness during exertion, especially when associated with chest pain or palpitations, should not automatically be attributed to fatigue or dehydration without appropriate assessment.
In more severe forms, fulminant myocarditis can develop, with rapid deterioration of cardiac function and the need for intensive care.

When urgent assessment is needed

Urgent medical care is necessary if the child has significant breathing difficulty, bluish or very pale skin, loss of consciousness, marked drowsiness or poor responsiveness, severe and persistent chest pain, palpitations associated with severe illness, or signs of poor perfusion such as cold extremities and extreme weakness.
In infants, inability to feed associated with very rapid breathing, marked sweating or progressively reduced responsiveness is a situation that should not simply be observed at home.

These signs are not specific to myocarditis and may be caused by other pediatric emergencies. Precisely for this reason, when a child appears seriously ill, the priority is clinical assessment rather than trying to determine the cause independently. In the event of loss of consciousness, severe breathing difficulty or rapid deterioration, it may be necessary to call 112 or 118.

How it is diagnosed and what happens afterward

The diagnostic pathway combines medical history and examination with an ECG, blood tests and an echocardiogram. Troponin may increase when there is myocardial injury, but a single normal value is not sufficient in every situation to rule out the disease. Cardiac magnetic resonance imaging has taken on an important role because it allows non-invasive assessment of myocardial edema, inflammation and injury.
Endomyocardial biopsy is not performed in every child: it is reserved for selected scenarios, especially when the disease is severe or when identifying the precise type of myocarditis may change treatment.

The course varies. Many children recover cardiac function, while others require longer follow-up because of persistent abnormalities, arrhythmias or ventricular dysfunction. After the acute phase, follow-up and the timing of return to school, play and sports are determined according to severity and test results.
Adolescents who participate in sports should not resume intense training simply because they feel better: return to activity requires clinical remission and cardiology assessment.

Frequently asked questions about myocarditis in children

What are the symptoms of myocarditis in children?
They vary greatly with age. In infants, rapid breathing, feeding difficulty, sweating, irritability or drowsiness may predominate; in older children and adolescents, chest pain, shortness of breath, fatigue, palpitations and reduced exercise tolerance are more common.

Can myocarditis in children look like a normal infection?
Yes. Fever, cough, vomiting, abdominal pain, fatigue and other nonspecific symptoms may initially suggest a respiratory or gastrointestinal infection. The appearance of cardiac signs or an unexpected deterioration requires reassessment.

When should a child be taken to the emergency department immediately?
Significant breathing difficulty, bluish or very pale skin, loss of consciousness, marked drowsiness or poor responsiveness, severe chest pain, palpitations with significant illness, or signs of poor perfusion require urgent assessment.

How is myocarditis diagnosed in a child?
Diagnosis integrates examination, ECG, blood tests, echocardiogram and, when indicated, cardiac magnetic resonance imaging. Endomyocardial biopsy is reserved for selected situations.

Can an adolescent with myocarditis return to sports?
Yes, but not during the active phase. Return to sports should occur after remission and cardiology follow-up, using criteria similar to those used in adults but adapted to age, development and type of activity.