What is the appropriate management and treatment for a patient with suspected myocarditis, particularly those with severe symptoms or a history of underlying heart disease?

Management and Treatment of Suspected Myocarditis

All patients with definite myocarditis—whether mild, moderate, or severe—require hospitalization at an advanced heart failure center, with fulminant cases transferred to centers with mechanical circulatory support capabilities. 1, 2

Initial Diagnostic Workup

When myocarditis is suspected based on cardiac symptoms (chest pain, dyspnea, palpitations, syncope), immediately obtain:

• ECG to identify arrhythmias, conduction abnormalities, or ST-segment changes 1
• High-sensitivity cardiac troponin (elevated in myocarditis, though only 34% sensitive in some cohorts) 1
• Transthoracic echocardiogram to assess ventricular function and wall motion abnormalities 1

Cardiology consultation is mandatory for patients with rising troponin and/or ECG or echocardiographic abnormalities. 1

Advanced Imaging

Cardiac MRI is recommended in all hemodynamically stable patients with suspected myocarditis to confirm the diagnosis using Lake Louise criteria. 1 The characteristic pattern shows epicardial or midwall late gadolinium enhancement (LGE), distinguishing it from ischemic cardiomyopathy which shows endocardial enhancement in coronary distributions. 1 Importantly, patients with normal CMR (normal LV volumes, normal ejection fraction, no LGE) have excellent prognosis regardless of symptoms. 3

Endomyocardial Biopsy

While the 2022 ACC guidelines and 2016 AHA statement differ on biopsy indications, biopsy should be strongly considered for rapidly progressive heart failure, suspected giant cell myocarditis, cardiac sarcoidosis, or eosinophilic myocarditis where specific immunosuppression may alter outcomes. 1, 2 The sensitivity is 80-85% for giant cell myocarditis but lower for lymphocytic myocarditis. 1

Acute Management by Severity

Mild to Moderate Myocarditis

Hospitalize at an advanced heart failure center for continuous cardiac monitoring. 1, 2 Approximately 75% of hospitalized myocarditis patients have uncomplicated courses with near-zero mortality. 4

Initiate guideline-directed medical therapy for heart failure:

• ACE inhibitors or ARBs for neurohormonal blockade 2, 5
• Beta-blockers only if hemodynamically stable, particularly for supraventricular arrhythmias 2, 5
• Aldosterone antagonists for mildly reduced LV function with stable hemodynamics 2
• Diuretics for volume management 5

Fulminant Myocarditis

Transfer immediately to centers with mechanical circulatory support expertise. 1, 2 Fulminant myocarditis carries 28% mortality at 60 days despite aggressive treatment, though survivors have better long-term prognosis than non-fulminant forms. 2

Initiate mechanical circulatory support urgently if shock persists despite pharmacologic therapy:

• Options include ECMO, percutaneous cardiopulmonary support, or intra-aortic balloon pump 2
• Early referral for cardiac transplantation evaluation 5

Immunosuppression: Highly Selective Use

Immunosuppression is NOT indicated for routine viral or lymphocytic myocarditis in adults. 2, 6

Consider immunosuppressive therapy ONLY for:

• Giant cell myocarditis 2, 4
• Cardiac sarcoidosis 2, 4
• Eosinophilic myocarditis 2, 4
• Immune checkpoint inhibitor-induced myocarditis (permanently discontinue immunotherapy and start high-dose methylprednisolone) 2
• Systemic autoimmune disorders (e.g., lupus) with myocardial involvement 4

COVID-19-Specific Considerations

Corticosteroids should be used for patients with myocarditis AND COVID-19 pneumonia requiring supplemental oxygen. 1 Intravenous corticosteroids may be considered for COVID-19 myocarditis with hemodynamic compromise or multisystem inflammatory syndrome in adults (MIS-A). 1

Critical Contraindications and Restrictions

NSAIDs: Absolutely Contraindicated

NSAIDs are contraindicated in myocarditis as animal models demonstrate increased inflammation and mortality. 1, 7 The exception is documented pericardial involvement, where NSAIDs, colchicine, and/or prednisone are reasonable. 1

Exercise Restriction: Mandatory

Complete exercise abstinence for 3-6 months is mandatory for all patients with clinical myocarditis. 1, 2 Sudden cardiac death has been reported in athletes after strenuous exertion during active myocarditis. 1, 8

Return to play criteria after 3-6 months:

• Absence of cardiopulmonary symptoms 1
• Resolution of laboratory evidence of myocardial injury 1
• Normalization of LV systolic function 1
• Absence of spontaneous/inducible arrhythmias on ECG monitoring and exercise stress testing 1

For athletes with COVID-19-related myocarditis, only 1 of 6 with clinical disease had resolution of CMR findings after 10 weeks, suggesting the 3-month minimum may be insufficient for some patients. 1

Arrhythmia Management

Acute arrhythmias typically resolve with resolution of inflammation and require supportive management. 2 Insert temporary pacemaker for symptomatic or high-grade AV block triggering ventricular tachyarrhythmias. 2, 6 Patients with QRS width >120 ms have higher risk of death or transplantation. 1

Follow-Up Surveillance

Perform follow-up testing at 3-6 months to assess recovery:

• Repeat echocardiography or cardiac MRI 2, 6
• Reassess cardiac biomarkers 2, 6
• Exercise stress testing and ambulatory rhythm monitoring before return to exercise 1

Long-term monitoring is essential: 21% of patients develop dilated cardiomyopathy during follow-up. 2, 6 Patients with persistent LGE on CMR may have increased risk of ventricular arrhythmias and cardiovascular death. 1

Common Pitfalls

• Do not discharge patients with definite myocarditis for outpatient management—even mild cases require hospitalization for monitoring. 1, 2
• Do not use empiric immunosuppression without biopsy confirmation of giant cell, eosinophilic, or sarcoid myocarditis. 2
• Do not allow return to exercise before 3 months even if symptoms resolve earlier—inflammatory changes persist longer than clinical improvement. 1
• Do not assume normal troponin excludes myocarditis—sensitivity is only 34% with standard assays. 1