What are the causes and treatment options for myocarditis in an adolescent patient?

Myocarditis in Adolescents: Causes and Treatment

Causes of Myocarditis in Adolescents

Viral infections are the predominant cause of myocarditis in adolescents, with enteroviruses, adenovirus, and parvovirus B19 being the most common pathogens. 1, 2

Infectious Etiologies

• Viral agents account for the majority of cases, including enteroviruses (most common), adenovirus, and parvovirus B19 1, 2
• Bacterial infections can cause myocarditis, including Lyme disease and diphtheria, which frequently present with heart block 3
• Chlamydia myocarditis has been implicated in sudden cardiac death in young athletes 3

Non-Infectious Causes

• Multisystem Inflammatory Syndrome in Children (MIS-C) associated with SARS-CoV-2 is an increasingly recognized cause, with older children more likely to develop myocarditis compared to younger children who present with Kawasaki-like features 3
• Hypersensitivity reactions to drugs or vaccines can trigger eosinophilic myocarditis 3
• Autoimmune conditions including lupus erythematosus can affect the myocardium 3
• Giant cell myocarditis is a severe form with dramatic clinical course that frequently affects young patients 3

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Treatment Approach

All adolescents with myocarditis must be hospitalized at an advanced heart failure center for continuous cardiac monitoring, as ventricular arrhythmias carry a 5.4-fold increased risk of cardiac arrest, mechanical circulatory support need, or death. 3, 4

Immediate Management and Risk Stratification

Hospitalization Requirements

• Transfer patients with fulminant myocarditis (presenting with cardiogenic shock) to centers with mechanical circulatory support expertise immediately 4
• Fulminant myocarditis has 58% short-term survival but paradoxically better long-term outcomes (93% alive without transplant at 11 years) compared to non-fulminant forms (45% at 11 years) 3
• All patients require continuous ECG monitoring, as electrical conduction abnormalities may develop after initial presentation 3

Diagnostic Monitoring

• Obtain ECG every 48 hours while hospitalized and at each follow-up visit to detect conduction abnormalities 3
• Monitor cardiac troponin and BNP/NT-proBNP levels sequentially to assess disease progression 3
• Perform echocardiography at presentation, then repeat at 7-14 days and 4-6 weeks minimum 3
• Consider cardiac MRI at 2-6 months post-acute illness for patients with moderate-to-severe LV dysfunction to evaluate for myocardial fibrosis and scarring 3

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Standard Medical Therapy

Initiate guideline-directed heart failure therapy with ACE inhibitors or ARBs for neurohormonal blockade once hemodynamically stable. 4

Heart Failure Management

• ACE inhibitors or ARBs are first-line for neurohormonal blockade 4
• Beta-blockers should be used cautiously and only if hemodynamically stable, particularly for supraventricular arrhythmias 4
• Aldosterone antagonists for patients with mildly reduced LV function and stable hemodynamics 4
• Diuretics for volume management as needed 1
• Titrate medications in the outpatient setting after discharge 4

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Arrhythmia and Conduction Abnormality Management

Insert a temporary pacemaker for symptomatic heart block or high-grade AV block that triggers ventricular tachyarrhythmias. 3, 4

Specific Arrhythmia Protocols

• Place patients with conduction abnormalities on telemetry while hospitalized 3
• Consider Holter monitoring at clinical follow-up for detected conduction issues 3
• Most acute arrhythmias resolve with resolution of inflammation and require only supportive management 4
• If persistent AV block develops, permanent pacing is indicated, but device selection must account for LV dysfunction extent and prognosis 3
• For refractory VT or VF not responding to 3-5 defibrillation attempts, initiate percutaneous cardiopulmonary support 3

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Mechanical Circulatory Support

Initiate mechanical circulatory support urgently if shock does not reverse rapidly with pharmacological therapy. 4

Support Options

• Percutaneous cardiopulmonary support, ECMO, or intra-aortic balloon pump are recommended for fulminant myocarditis with refractory shock 3, 4
• Aggressive hemodynamic support is essential to bridge the acute but often curable stage of disease 3

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Immunosuppression: Limited Role

Immunosuppression is generally NOT indicated for typical viral myocarditis in adolescents, but should be considered for specific subtypes including giant cell myocarditis, cardiac sarcoidosis, and eosinophilic myocarditis. 4, 5

When to Consider Immunosuppression

• Giant cell myocarditis requires immunosuppressive therapy due to severe prognosis 3, 4
• Eosinophilic myocarditis may benefit from corticosteroid therapy, though efficacy is not well-supported 3
• Cardiac sarcoidosis warrants immunosuppression 4
• MIS-C patients require immunomodulatory treatment with IVIG and corticosteroids, particularly those with life-threatening manifestations 3
• Classic immunosuppressive drugs (cyclosporine A, cyclophosphamide) are not effective for lymphocytic myocarditis and may interfere with host immunity needed to control persistent viral infection 5

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Critical Activity Restrictions

Mandate complete exercise abstinence for 3-6 months after diagnosis, as sustained aerobic exercise during acute viral myocarditis increases mortality and can cause sudden death. 4

Specific Restrictions

• Prohibit all competitive sports participation for the entire 3-6 month period 4
• This restriction is critical as myocarditis is an important cause of sudden cardiac death in young athletes 3

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Medications to Avoid

Absolutely avoid NSAIDs due to increased inflammation and mortality risk in myocarditis. 4

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Follow-Up Surveillance

Perform follow-up testing at 3-6 months to assess recovery, including repeat echocardiography or cardiac MRI and reassessment of cardiac biomarkers. 4

Long-Term Monitoring

• Repeat echocardiography at minimum 7-14 days, 4-6 weeks, and consider at 1 year for those with acute cardiac involvement 3
• Patients with LV dysfunction and coronary artery aneurysms require more frequent echocardiograms 3
• Monitor for development of dilated cardiomyopathy, which occurs in 21% of myocarditis patients during long-term follow-up 4
• Cardiac MRI at 2-6 months allows evaluation for myocardial fibrosis and scarring, which represent potential long-term complications 3

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Special Considerations for MIS-C

For adolescents with MIS-C-associated myocarditis, the treatment approach differs from typical viral myocarditis:

• Initiate immunomodulatory treatment with IVIG and corticosteroids, particularly for life-threatening presentations with shock 3
• Older children with MIS-C are more likely to develop myocarditis and shock compared to younger children who present with Kawasaki-like features 3
• A stepwise approach to immunomodulatory treatment is recommended, with treatment intensity depending on severity of presentation 3