How should I work up and manage a previously healthy child, adolescent, or young adult presenting with acute chest pain, dyspnea, palpitations, syncope, or unexplained heart failure after a recent viral prodrome, when viral myocarditis is suspected?

Workup and Management of Suspected Viral Myocarditis in Young Patients

When a previously healthy child, adolescent, or young adult presents with chest pain, dyspnea, palpitations, syncope, or unexplained heart failure after a recent viral illness, immediately obtain an ECG, high-sensitivity cardiac troponin, and echocardiogram—if any of these are abnormal, consult cardiology urgently and hospitalize at an advanced heart failure center. 1, 2

Initial Diagnostic Workup

Immediate Testing (Within Hours of Presentation)

• 12-lead ECG: Look specifically for diffuse T-wave inversion, ST-segment elevation without reciprocal ST-segment depression, prolongation of QRS complex duration, AV blocks (I-III), bundle branch blocks, or new Q waves 3, 2
• High-sensitivity cardiac troponin: Obtain serial measurements if initially elevated; elevation is required for diagnosis but levels may be only mildly elevated despite severe ventricular dysfunction 3, 1, 2
• Transthoracic echocardiography: Assess for left ventricular wall motion abnormalities in a noncoronary distribution, reduced ejection fraction, ventricular dilatation, increased wall thickness from edema, and pericardial effusion 3, 1, 2

Additional Laboratory Studies

• Complete blood count, electrolytes, BUN, creatinine, glucose, calcium, magnesium, and phosphorus 3
• Chest radiograph to evaluate for pulmonary edema or cardiomegaly 3
• Viral serology has limited clinical utility and is not routinely recommended 3

Advanced Imaging

• Cardiac MRI: Obtain in all hemodynamically stable patients with suspected myocarditis to confirm diagnosis; look for nonischemic late gadolinium enhancement pattern with prolonged native T1 and T2 relaxation times 3, 1, 2
• CMR is the gold standard noninvasive test and should be performed before discharge if the patient is stable 3, 1

Endomyocardial Biopsy

• Biopsy is the definitive diagnostic test but has low yield (5-10%) when strict histologic criteria are applied 3
• Reserve for cases where diagnosis remains uncertain after noninvasive testing or when specific etiologies requiring targeted therapy (giant cell myocarditis, cardiac sarcoidosis, eosinophilic myocarditis) are suspected 4

Risk Stratification and Hospitalization Decisions

Mandatory Hospitalization Criteria

All patients with definite myocarditis require hospitalization at an advanced heart failure center 3, 1, 4

Definite myocarditis is defined by: cardiac symptoms (chest pain, dyspnea, palpitations, syncope) PLUS elevated troponin PLUS abnormal findings on ECG/echo/CMR consistent with active myocarditis 3

Fulminant Myocarditis (Requires Tertiary Center Transfer)

Transfer immediately to centers with mechanical circulatory support and transplant capabilities if patient presents with: 3, 1, 4

• Cardiogenic shock (occurs in 27% of COVID-19-associated myocarditis) 2
• Severe hemodynamic compromise requiring inotropic support
• Sustained ventricular arrhythmias requiring urgent intervention 2
• Advanced AV block causing symptomatic bradycardia 2

Fulminant myocarditis carries 28% mortality at 60 days but has better long-term prognosis than non-fulminant forms if patients survive the acute phase 4

Acute Management

Supportive Care and Heart Failure Therapy

• Initiate guideline-directed medical therapy for heart failure before discharge: ACE inhibitors or ARBs for neurohormonal blockade 3, 1, 4
• Beta-blockers: Use only in hemodynamically stable patients with supraventricular arrhythmias; avoid in compromised patients as they can precipitate cardiogenic shock 1, 4
• Aldosterone antagonists: Consider for patients with mildly reduced left ventricular function and stable hemodynamics 4
• Fluid restriction and supplemental oxygen as needed 5

Mechanical Circulatory Support

Initiate urgently if shock does not reverse rapidly with pharmacological therapy; options include percutaneous cardiopulmonary support, ECMO, or intra-aortic balloon pump 4

Immunosuppression (Generally NOT Indicated)

Critical caveat: The Myocarditis Treatment Trial found no beneficial effect of prednisone with azathioprine or cyclosporine in patients with biopsy-proven lymphocytic myocarditis 3

Exceptions where immunosuppression IS indicated: 4

• Giant cell myocarditis
• Cardiac sarcoidosis
• Eosinophilic myocarditis
• Immune checkpoint inhibitor-induced myocarditis (use high-dose methylprednisolone 1000 mg/day IV followed by oral prednisone 1 mg/kg/day)

COVID-19-Specific Considerations

• Corticosteroids are indicated for myocarditis with concurrent COVID-19 pneumonia requiring supplemental oxygen 3, 1
• Consider IV corticosteroids for hemodynamic compromise or multisystem inflammatory syndrome in adults (MIS-A) 3, 1

Pericardial Involvement

If pericardial involvement is suspected, treatment with NSAIDs, colchicine, and/or prednisone is reasonable 3

Important warning: Avoid NSAIDs in isolated myocarditis without pericardial involvement due to increased inflammation and mortality risk 1

Arrhythmia Management

• Acute arrhythmias often resolve with resolution of inflammation; management is primarily supportive 4
• Insert temporary pacemaker if symptomatic or high-grade AV block triggers ventricular tachyarrhythmias 4
• Ventricular arrhythmias are frequent and myocarditis accounts for a large proportion of sudden cardiac deaths in young people 6

Activity Restriction

Mandate complete exercise abstinence for 3-6 months after diagnosis 3, 1, 4

This is critical because sustained aerobic exercise during acute viral myocarditis increases mortality and sudden death risk 1

Return-to-Play Criteria (After 3-6 Months)

Before resuming competitive sports or vigorous exercise, ALL of the following must be met: 3, 1

• Absence of cardiopulmonary symptoms
• Resolution of laboratory evidence of myocardial injury (normal troponin)
• Normalization of left ventricular systolic function on echocardiography
• Absence of spontaneous or inducible arrhythmias on ECG monitoring and exercise stress testing

Follow-Up Surveillance

3-6 Month Reassessment

Perform comprehensive follow-up testing including: 3, 1, 4

• ECG
• Echocardiogram or cardiac MRI to assess ventricular function
• Cardiac biomarkers (troponin)
• Ambulatory rhythm monitor
• Exercise stress testing (if reduced LV systolic function) to assess for appropriate augmentation with exercise 3

Long-Term Prognosis

• Most cases of viral myocarditis are self-limited with complete recovery 3, 7
• Resolution within 3 months occurs in many cases 2
• Dilated cardiomyopathy develops in 21% of patients during long-term follow-up 4
• In the Big Ten COVID-19 registry, 41% of athletes had complete resolution of CMR abnormalities after median 8 weeks, though only 1 of 6 with clinical myocarditis had resolution after 10 weeks 3

Common Pitfalls to Avoid

• Do not dismiss mildly elevated troponin levels: Troponin may be only mildly elevated despite severe left ventricular dysfunction, which strongly suggests inflammatory cardiomyopathy 8
• Do not use NSAIDs for isolated myocarditis: They increase inflammation and mortality when pericardial involvement is absent 1
• Do not start beta-blockers in hemodynamically unstable patients: This can precipitate cardiogenic shock 1, 4
• Do not allow early return to exercise: Even if symptoms resolve quickly, maintain 3-6 month restriction to prevent sudden death 3, 1, 4
• Do not pursue routine immunosuppression: This has no proven benefit in typical viral myocarditis and may increase infection risk 3