Today, I review, link to, embed, and excerpt from The Cribsiders‘ #128: Hearts on Fire – Myocarditis*.

*Rago, AR, Laks, J, Kelly, JM, Masur, S, Chiu C. “128: Hearts on Fire – Myocarditis”. The Cribsiders Pediatric Podcast. https:/www.thecribsiders.com/ December 18, 2024

All that follows is from the above resource.

Audio

Summary:

Does thinking about myocarditis make your chest hurt? In this episode, we have a fantastic heart-to-heart with Dr. Jessica Laks (Heart Failure and Transplant at Johns Hopkins All Children’s Hospital). Together, we dive into the complexities of myocarditis – how to recognize the signs, how to triage patients, and what tests to order. Sit back, relax, and keep an open heart as she drops the heart facts about myocarditis.

Myocarditis Pearls

1. Consider myocarditis in a patient with a viral prodrome with nonspecific symptoms (fatigue, poor PO, abdominal pain), and tachycardia.
2. Mild myocarditis can rapidly progress to fulminant disease with signs of cardiogenic shock.
3. Children with myocarditis may develop arrhythmias and require treatment with antiarrhythmics.
4. ECG typically demonstrates sinus tachycardia for age and non-specific changes such as ST-segment changes (flattening or depression), T-wave abnormalities, and/or T-wave inversions. An ECG with a low voltage QRS interval should raise suspicion for myocarditis, due to either overall inflammation or an associated pericardial effusion.
5. Troponin is a sign of myocardial injury, but is not specific to myocarditis and does not correlate with disease severity.

Myocarditis Notes

What is myocarditis?

“Myo” – muscle, “card” – heart, “itis” – inflammation

Together, myocarditis means inflammation of the heart muscle.

Myocarditis ranges in severity, from a subacute presentation with mild viral-type symptoms to fulminant heart failure with severe systolic and diastolic dysfunction. Children can present with non-specific symptoms of fatigue and poor intake.

• Mild disease: May have normal to mildly abnormal labs, and echo may be normal. Depending on parental comfort level, they may be observed at home or on the floor without telemetry.
• Severe disease: evidence of decreased function and/or an abnormal electrocardiogram (ECG). Admit to the intensive care unit (ICU) on telemetry. Given the uncertainty of where the patient is in the disease process, they may either be clinically stable or deteriorate further.

The observed incidence of myocarditis in children is roughly 1-2 per 100,000 person-years (Arola et al. 2017). That said, the incidence may be greater given the number of children who may not present to care.

What is the pathophysiology of myocarditis?

The pathogenesis of myocarditis depends on the specific etiology.

Editor’s Note: In viral myocarditis, death of cardiomyocytes, endothelial cells, and stromal cells activates the innate immune response through several mechanisms, leading to further activation of an inflammatory response and infiltration of cardiomyocytes by immune cells. This infiltration can lead to the development of fibrosis and cardiomyopathy. (Law et al. 2021)

When should I suspect myocarditis?

Myocarditis should be suspected in a child with new-onset signs and symptoms of heart failure with left ventricular systolic dysfunction, particularly if there is no evidence for other etiologies, such as congenital heart disease, coronary abnormality, or familial cardiomyopathy.

Careful triage and clinical stabilization takes precedence over creating a differential diagnosis, particularly in the acute stage. It is important to focus on ABCs (airway, breathing, and circulation) of resuscitation.

Initial presentation:

• Vitals may show tachycardia, tachypnea, decreased blood pressure, bounding pulses
• Arrhythmias – the most common are ventricular tachycardia, ventricular fibrillation, and atrioventricular (AV) block (Miyake et al. 2014).
• May have an associated pericarditis, so they may be more comfortable sitting up rather than laying down.

Signs of heart failure:

• Left ventricular systolic dysfunction, with the heart not squeezing properly. PAtients are unable to augment their cardiac output with increased contractility, so they become tachycardic.
• Diastolic dysfunction may be present due to the heart not relaxing properly.
• Deterioration following fluid bolus is concerning for myocarditis or cardiomyopathy
  • Pearl: This is a sign that the patient’s cardiac LV systolic function is decreased, end-diastolic pressure in the LV is high, and they cannot handle extra volume. As a result, blood will flow backwards into the lower pressure left atrium, into the lungs, and create pulmonary edema causing worsening tachypnea and increased work of breathing
• Right-sided heart failure secondary to left-sided heart failure may be present. Exam findings suggestive of right-sided heart failure include hepatomegaly and peripheral edema.

How is myocarditis diagnosed?

start here