Overview
Definition:
Myocarditis is inflammation of the heart muscle (myocardium), which can reduce the heart's ability to pump blood and cause arrhythmias
In children, common etiologies include viral infections and, more recently, MIS-C.
Epidemiology:
Viral myocarditis is the most common cause of acquired heart disease in children in developed countries, with an estimated incidence of 1.1 to 10 per 100,000 children
MIS-C, a post-infectious sequela of SARS-CoV-2, emerged in 2020 and presents with cardiac involvement in a significant proportion of cases.
Clinical Significance:
Myocarditis can lead to severe morbidity and mortality, including acute heart failure, cardiogenic shock, malignant arrhythmias, and sudden cardiac death
Early recognition and appropriate management are crucial for improving outcomes in pediatric patients, making it a key topic for DNB and NEET SS examinations.
Mis C
Definition:
MIS-C is a rare but serious condition that causes different parts of the body to become inflamed, including the heart, lungs, kidneys, brain, skin, eyes, or gastrointestinal organs
It typically occurs 2-6 weeks after SARS-CoV-2 infection, even in asymptomatic or mild cases.
Epidemiology:
Primarily affects children aged 1 to 14 years, with a peak incidence between 5 and 13 years
Affects children of all races and ethnicities, with higher reported rates in Black and Hispanic children.
Clinical Presentation:
Persistent fever (>38.5°C for ≥5 days)
Rash
Conjunctivitis (bilateral, non-exudative)
Mucocutaneous changes (erythema, edema of hands/feet, cracked lips, strawberry tongue)
Gastrointestinal symptoms (abdominal pain, vomiting, diarrhea)
Cardiovascular involvement (myocarditis, valvulitis, coronary artery aneurysms, pericarditis, hypotension, shock)
Neurological symptoms (headache, confusion)
Respiratory distress
Laboratory findings of inflammation (elevated CRP, ESR, ferritin, D-dimer)
Lymphadenopathy.
Diagnostic Criteria:
Case definitions from CDC/WHO: ≥5 days fever plus ≥4 of the following: rash, bilateral non-purulent conjunctivitis/erythema, oral mucosal changes, polymorphous rash, edema/erythema of extremities, peripheral desquamation
hypotension/shock
current or recent SARS-CoV-2 infection
elevated inflammatory markers
no other plausible diagnosis
evidence of multi-system inflammation.
Cardiac Involvement In Mis C:
Myocarditis is common in MIS-C, often presenting with ventricular dysfunction, dilated cardiomyopathy, and elevated troponins
Coronary artery dilation or aneurysms are also a significant concern, requiring careful monitoring with echocardiography and potentially serial CMR.
Role Of Cardiac Mri
Indications:
Suspicion of myocarditis (viral or MIS-C)
Differentiating myocarditis from other causes of heart failure or chest pain
Assessing extent and severity of myocardial inflammation and fibrosis
Monitoring response to treatment
Evaluating for sequelae like dilated cardiomyopathy or coronary artery abnormalities.
Findings In Myocarditis:
Myocardial edema (T2-weighted imaging)
Myocardial scarring/fibrosis (late gadolinium enhancement - LGE), typically in a non-ischemic pattern (mid-myocardial or subepicardial)
Reduced ventricular function and chamber dilation.
Findings In Mis C Cardiac Involvement:
Similar to viral myocarditis with edema and LGE
Also crucial for detecting coronary artery dilation/aneurysms and pericardial effusion.
Advantages:
Non-invasive
Provides comprehensive functional and tissue characterization of the myocardium
Can detect inflammation and fibrosis that may not be apparent on echocardiography
Superior spatial resolution for LGE compared to echocardiography.
Management Principles
Supportive Care:
Admission to hospital, often requiring pediatric intensive care unit (PICU) monitoring
Oxygen support
Fluid management
Close monitoring of hemodynamics and arrhythmias.
Medical Management Viral:
Diuretics for heart failure (e.g., furosemide)
Afterload reduction (e.g., ACE inhibitors like enalapril, beta-blockers like carvedilol or metoprolol)
Inotropic support if cardiogenic shock (e.g., dopamine, dobutamine)
Mechanical circulatory support (e.g., ECMO) for refractory shock.
Medical Management Mis C:
Intravenous immunoglobulin (IVIG)
Corticosteroids (e.g., methylprednisolone)
Anticoagulation for coronary artery aneurysms (aspirin, low-molecular-weight heparin)
Supportive care for heart failure and shock as above
Specific management for coronary artery aneurysms involves aspirin and anticoagulation, and potential referral for advanced therapies if aneurysms are large or progressive.
Contraindications:
NSAIDs and some immunosuppressants may be relatively contraindicated in acute viral myocarditis unless specific indications exist.
Complications And Prognosis
Potential Complications:
Acute heart failure
Cardiogenic shock
Malignant arrhythmias (ventricular tachycardia, ventricular fibrillation)
Myocarditis-induced dilated cardiomyopathy
Thromboembolic events
Death
Coronary artery aneurysms (especially in MIS-C).
Factors Affecting Prognosis:
Severity of initial presentation
Ejection fraction on diagnosis
Presence of significant LGE on CMR
Development of dilated cardiomyopathy
Response to treatment
Etiology (some viral causes have poorer prognosis than others).
Prognosis:
Prognosis varies widely
Many children recover full cardiac function
However, a significant minority can develop chronic heart failure or dilated cardiomyopathy
MIS-C carries a risk of coronary artery aneurysms, which requires long-term follow-up and management.
Key Points
Exam Focus:
Differentiate between viral myocarditis and MIS-C presentation
Recognize key diagnostic clues for each
Understand the role of ECG, troponins, echo, and CMR
Know the core management principles for heart failure and shock in pediatric myocarditis
Understand specific MIS-C management (IVIG, steroids) and cardiac sequelae (coronary aneurysms).
Clinical Pearls:
Always consider myocarditis in a child with unexplained heart failure or arrhythmias, especially after a viral prodrome
Cardiac MRI is invaluable for confirming diagnosis, assessing severity, and guiding management of myocarditis
Early recognition of MIS-C and its cardiac manifestations is critical to prevent long-term sequelae.
Common Mistakes:
Attributing heart failure symptoms solely to pneumonia or sepsis without considering cardiac involvement
Delaying cardiac imaging (echo/CMR) in suspected myocarditis
Inadequate management of cardiogenic shock
Underestimating the risk of coronary artery aneurysms in MIS-C and failing to initiate appropriate anticoagulation/antiplatelet therapy.