What is the initial treatment approach for a patient diagnosed with myocarditis?

Initial Treatment of Myocarditis

All patients with definite myocarditis should be hospitalized at an advanced heart failure center and treated with guideline-directed medical therapy for heart failure, while immunosuppression is reserved only for specific subtypes (giant cell, cardiac sarcoidosis, eosinophilic) or immune checkpoint inhibitor-induced cases. 1

Immediate Hospitalization and Risk Stratification

• Hospitalize all patients with mild or moderate myocarditis at an advanced heart failure center, as this condition carries significant risk even in seemingly stable presentations 1
• Transfer patients with fulminant myocarditis (hemodynamic instability, refractory arrhythmias, severe acute heart failure) to centers with mechanical circulatory support and transplant capabilities 2, 1
• Fulminant myocarditis carries 28% mortality at 60 days despite aggressive treatment, though survivors have better long-term prognosis (93% alive without transplant at 11 years) compared to non-fulminant forms (45%) 1, 3

Standard Medical Therapy (First-Line Treatment)

Initiate guideline-directed heart failure therapy before discharge:

• ACE inhibitors or ARBs for neurohormonal blockade should be started in all patients with heart failure 2, 1
• Beta-blockers should be used cautiously and only in hemodynamically stable patients, particularly those with supraventricular arrhythmias, as they can precipitate cardiogenic shock in compromised patients 2, 1
• Aldosterone antagonists for patients with mildly reduced left ventricular function and stable hemodynamics 1
• Titrate these medications in the outpatient setting after discharge 1

Immunosuppression (Etiology-Specific)

Corticosteroids are NOT routinely indicated for typical viral myocarditis. Immunosuppression should only be used in specific circumstances:

When to Use Corticosteroids:

• Giant cell myocarditis, cardiac sarcoidosis, or eosinophilic myocarditis (biopsy-proven) 1, 4
• Immune checkpoint inhibitor-induced myocarditis: Permanently discontinue the immunotherapy and start high-dose methylprednisolone 1000 mg/day IV followed by oral prednisone 1 mg/kg/day 5, 1
• COVID-19 myocarditis with concurrent pneumonia requiring supplemental oxygen, hemodynamic compromise, or fulminant myocarditis with biopsy-proven severe inflammatory infiltrates 2

Steroid-Refractory Cases:

• For high-grade myocarditis with hemodynamic instability not responding to corticosteroids, consider antithymocyte globulin, infliximab (except in heart failure patients), mycophenolate mofetil, or abatacept 5

Mechanical Circulatory Support

• Initiate mechanical circulatory support urgently if shock does not reverse rapidly with pharmacological therapy 1
• Options include percutaneous cardiopulmonary support, ECMO, or intra-aortic balloon pump 1
• This applies to approximately 2-9% of patients who develop hemodynamic instability 4

Arrhythmia Management

• Insert temporary pacemaker if symptomatic or high-grade AV block triggers ventricular tachyarrhythmias 1
• Continuous ECG monitoring is mandatory to detect ventricular tachycardia, complete heart block, and QRS widening (>120 ms predicts higher risk of death or transplantation) 3
• Most acute arrhythmias resolve with resolution of inflammation and management is supportive 1

Medications to AVOID

• NSAIDs should be avoided in isolated myocarditis without pericardial involvement due to increased inflammation and mortality risk 2
• NSAIDs, colchicine, or prednisone are reasonable only for pericardial involvement 2

Activity Restriction (Critical for Mortality Reduction)

• Mandate complete exercise abstinence for 3-6 months after diagnosis, as sustained aerobic exercise during acute viral myocarditis increases mortality and sudden death risk 2, 1
• Return-to-play criteria at 3-6 months require: absence of cardiopulmonary symptoms, resolution of myocardial injury markers, normalization of LV systolic function, and absence of arrhythmias on ECG monitoring and exercise stress testing 2

Follow-Up Surveillance Protocol

At 3-6 months after presentation, perform:

• ECG to assess for persistent conduction abnormalities 2
• Echocardiogram or cardiac MRI to assess ventricular function recovery 2, 1
• Ambulatory rhythm monitor 2
• Cardiac biomarker reassessment 1
• Note that dilated cardiomyopathy develops in 21% of patients during long-term follow-up 1

Common Pitfalls to Avoid

• Do not routinely use immunosuppression for typical viral myocarditis—this is only for specific histologic subtypes 1, 4
• Do not start beta-blockers in hemodynamically unstable patients—this can precipitate cardiogenic shock 2
• Do not allow early return to exercise—this significantly increases mortality risk 2, 1
• Do not discharge without initiating ACE inhibitors/ARBs—these should be started before discharge in all heart failure patients 2