Overview
Definition:
Pediatric myocarditis is an inflammatory condition of the heart muscle, often infectious in origin, leading to impaired cardiac function
Cardiogenic shock in children is a state of hypoperfusion due to cardiac dysfunction, characterized by decreased cardiac output and inadequate tissue oxygenation, frequently a complication of severe myocarditis.
Epidemiology:
Myocarditis is a rare but serious condition in children, with an incidence estimated between 1-2 per 100,000 children per year
Viral etiologies are most common, including enteroviruses (Coxsackie B, echovirus), adenovirus, parvovirus B19, and human herpesvirus-6
Non-viral causes include bacterial infections, toxins, and autoimmune diseases
Cardiogenic shock complicates approximately 5-10% of severe pediatric myocarditis cases.
Clinical Significance:
Rapid recognition and management of pediatric myocarditis and impending cardiogenic shock are crucial due to the high morbidity and mortality
Inadequate cardiac output leads to organ damage and potential irreversible sequelae
Understanding the presentation, diagnostic workup, and treatment strategies is vital for all pediatric residents and those preparing for DNB and NEET SS examinations.
Clinical Presentation
Symptoms:
Typical symptoms include fever
Irritability or lethargy
Poor feeding or vomiting
Respiratory distress, characterized by tachypnea and retractions
Cough, sometimes productive
Chest pain, often non-specific or referred
Syncope or near-syncope
Signs of poor perfusion, such as pallor, mottling, or cool extremities
Acute heart failure symptoms, including hepatomegaly and edema.
Signs:
Tachycardia disproportionate to fever
Hypotension (late sign of shock)
Gallop rhythm (S3, S4)
Murmurs of mitral or tricuspid regurgitation
Rales or crackles on lung auscultation
Jugular venous distension
Cool, clammy skin
Diminished peripheral pulses
Altered mental status.
Diagnostic Criteria:
There are no universally established diagnostic criteria for pediatric myocarditis, but diagnosis is based on a combination of clinical suspicion, elevated cardiac biomarkers, ECG abnormalities, echocardiographic findings, and sometimes myocardial biopsy
For cardiogenic shock, a persistent state of inadequate tissue perfusion with evidence of cardiac dysfunction, often defined by hypotension (e.g., < 70 mmHg + (2 x age in years) systolic BP for children > 1 year) or signs of end-organ hypoperfusion in the context of cardiac failure.
Diagnostic Approach
History Taking:
Recent viral illness (URI, gastroenteritis)
Exposure to sick contacts
History of Kawasaki disease or other inflammatory conditions
Immunization status
Medications and toxin exposures
Family history of cardiac disease
Duration and progression of symptoms
Red flags: syncope, severe dyspnea, significant pallor, or cyanosis.
Physical Examination:
Perform a thorough cardiopulmonary examination
Assess for signs of heart failure (JVP, hepatomegaly, edema, crackles)
Evaluate peripheral perfusion (capillary refill time, pulses, skin temperature, mottling)
Assess mental status and level of consciousness
Monitor vital signs meticulously, including blood pressure for hypotension.
Investigations:
Complete Blood Count (CBC) with differential: may show leukocytosis
Inflammatory markers: ESR, CRP elevated
Cardiac enzymes: Troponin I or T elevated (highly sensitive and specific)
BNP or NT-proBNP elevated (indicating myocardial stretch/strain)
Electrocardiogram (ECG): may show sinus tachycardia, ST-segment and T-wave abnormalities, arrhythmias, conduction delays, or PR depression
Chest X-ray (CXR): cardiomegaly, pulmonary venous congestion, pleural effusions
Echocardiogram (ECHO): crucial for assessing ventricular function (ejection fraction, fractional shortening), wall motion abnormalities, chamber dilation, pericardial effusion, and valve function
Myocardial biopsy: gold standard but invasive, reserved for ambiguous cases or when specific etiologies are suspected (e.g., giant cell myocarditis)
Polymerase Chain Reaction (PCR) of blood or myocardial tissue: to identify specific viral pathogens.
Differential Diagnosis:
Sepsis with distributive shock
Anaphylaxis
Hemorrhage
Pulmonary embolism
Congenital heart disease with decompensation
Arrhythmias causing hemodynamic instability
Pericardial tamponade
Severe anemia
Respiratory distress syndrome.
Management
Initial Management:
Immediate ABC assessment and stabilization
Airway management: supplemental oxygen, intubation if necessary for respiratory failure or shock
Breathing: mechanical ventilation if indicated
Circulation: establish IV access, fluid resuscitation judiciously (avoid fluid overload in potential heart failure), monitor cardiac rhythm
Correct metabolic abnormalities (e.g., hypoglycemia, electrolyte imbalances)
Early recognition of shock and initiation of inotropic support.
Medical Management:
Inotropic support: Dobutamine is the first-line agent for improving contractility
Dopamine can be used, especially if hypotension is prominent, due to its chronotropic and vasopressor effects
Epinephrine is reserved for refractory shock or severe hypotension
Vasodilators (e.g., milrinone, nitroprusside) may be considered cautiously to reduce afterload once adequate perfusion is achieved
Diuretics (e.g., furosemide) for fluid overload and heart failure symptoms
Steroids and immunosuppressants are generally not indicated in typical viral myocarditis but may be considered in specific autoimmune or giant cell myocarditis
Antivirals are rarely effective once symptoms are established
Beta-blockers are usually avoided in the acute phase of myocarditis with impaired LV function, but may be considered for recovery and long-term management.
Surgical Management:
Rarely indicated in the acute phase
May be considered for mechanical circulatory support in refractory cardiogenic shock
ECMO (Extracorporeal Membrane Oxygenation) can be a bridge to recovery or cardiac transplantation.
Supportive Care:
Continuous cardiac monitoring (ECG, SpO2, BP)
Strict fluid balance and intake/output monitoring
Mechanical ventilation and ventilator support as needed
Nutritional support: adequate caloric intake, consider enteral feeding if prolonged illness
Pain and sedation management
Infection control measures
Family support and education.
Complications
Early Complications:
Progressive cardiogenic shock refractory to medical management
Arrhythmias (supraventricular or ventricular tachycardias, heart block)
Myocardial rupture or perforation (rare)
Pericardial effusion and tamponade
Acute kidney injury
Hepatic dysfunction
Multi-organ failure.
Late Complications:
Dilated cardiomyopathy
Chronic heart failure
Sudden cardiac death
Restrictive cardiomyopathy (rare)
Mural thrombus formation leading to embolic events.
Prevention Strategies:
Prompt diagnosis and aggressive management of viral infections can potentially reduce the incidence of myocarditis
Strict adherence to management protocols for acute myocarditis and cardiogenic shock
Regular follow-up to monitor for late complications and progression to dilated cardiomyopathy.
Prognosis
Factors Affecting Prognosis:
Severity of initial illness and degree of myocardial dysfunction
Presence and severity of cardiogenic shock
Etiology of myocarditis (e.g., giant cell myocarditis has a poorer prognosis)
Development of complications like arrhythmias or heart failure
Age of the child (neonates and infants have a worse prognosis)
Promptness and effectiveness of treatment.
Outcomes:
Outcomes vary widely
Mild cases may resolve completely with full recovery of cardiac function
Severe cases with persistent heart failure or dilated cardiomyopathy have a poorer prognosis, requiring long-term medical management and potentially cardiac transplantation
Mortality in pediatric myocarditis with cardiogenic shock can be as high as 30-50% if not managed aggressively.
Follow Up:
Long-term follow-up is essential for all children with myocarditis, especially those with significant myocardial dysfunction or cardiogenic shock
This typically involves regular cardiology visits with serial echocardiograms to assess for recovery of left ventricular function and monitor for development of dilated cardiomyopathy or arrhythmias
ECG monitoring and Holter monitoring may be indicated
Genetic counseling might be considered if a familial predisposition is suspected.
Key Points
Exam Focus:
Recognize the subtle and diverse presentation of pediatric myocarditis
Differentiate from other causes of shock in children
Understand the stepwise approach to management of cardiogenic shock (inotropes first, then consider vasopressors/vasodilators)
Key ECG and ECHO findings are high-yield
Know the indications for mechanical circulatory support (e.g., ECMO).
Clinical Pearls:
Think myocarditis in any child with unexplained fever, respiratory distress, and cardiac dysfunction
Always consider viral etiologies first
Echocardiography is your most important diagnostic tool for assessing cardiac function
Be aggressive with inotropic support in shock, but be cautious with fluids
Early involvement of pediatric cardiology and critical care teams is paramount.
Common Mistakes:
Delayed recognition of shock due to subtle signs
Over-resuscitation with fluids leading to pulmonary edema
Inadequate or delayed initiation of inotropic support
Misinterpreting ECG findings in a young child
Not performing a thorough echocardiogram to assess ventricular function and wall motion
Failing to consider myocarditis in the differential diagnosis of acute respiratory distress or cardiac failure.