What are the treatment guidelines for myocarditis?

Myocarditis Treatment Guidelines

Immediate Management and Hospitalization

All patients with definite myocarditis, even if mild or moderate in severity, should be hospitalized, ideally at an advanced heart failure center. 1

Mandatory Hospital Admission Criteria

Patients require immediate hospitalization and intensive monitoring if they present with any of the following:

• Ventricular arrhythmias or heart block - these patients need prolonged ECG monitoring and telemetry 2, 1, 3
• Progressive wall motion abnormalities with deteriorating left ventricular function on echocardiography 4
• Persistent or fluctuating troponin concentrations 4
• Widening QRS complex (>120 ms) 4
• Frequent non-sustained ventricular arrhythmias 4
• Hemodynamic instability requiring inotropic support 5

Once cardiac toxicity is suspected, immediate cardiology consultation and ICU-level monitoring is recommended. 2

Initial Diagnostic Workup

Before initiating treatment, establish the diagnosis with:

• 12-lead ECG to assess for conduction abnormalities, ST-segment changes, and QRS widening 1, 3
• Cardiac biomarkers including troponin and creatine kinase levels 2, 1
• Transthoracic echocardiogram to evaluate ventricular function and wall motion abnormalities 1, 3
• Cardiac MRI in hemodynamically stable patients to confirm diagnosis and assess extent of inflammation 1, 3
• Endomyocardial biopsy remains the gold standard, particularly for life-threatening presentations or when specific etiologies (giant cell myocarditis, cardiac sarcoidosis) are suspected 1, 3

Standard Medical Therapy

Heart Failure Management

Initiate guideline-directed medical therapy for heart failure before discharge and titrate in the outpatient setting. 1

For patients presenting with heart failure symptoms:

• ACE inhibitors or ARBs for neurohormonal blockade 4, 6
• Beta-blockers for patients with supraventricular arrhythmias, if hemodynamically stable 1, 4
• Low-dose aldosterone antagonists for patients with mildly reduced left ventricular function and stable hemodynamics 1
• Diuretics for volume management 6
• Digoxin if indicated for rate control 6

Restrict physical activity - competitive sports should be avoided for 3-6 months after diagnosis. 1

Management of Severe and Fulminant Myocarditis

Mechanical Circulatory Support

Patients with fulminant myocarditis should be managed at centers with expertise in advanced heart failure. 1

For patients developing cardiogenic shock despite optimal medical management:

• Mechanical circulatory support may be required, including percutaneous cardiopulmonary support or intra-aortic balloon pump 1, 4
• Initiate support early if ventricular tachycardia or ventricular fibrillation is refractory to 3-5 defibrillation attempts 4

The short-term mortality for fulminant myocarditis is approximately 28% at 60 days for those requiring mechanical support, though paradoxically, survivors of fulminant myocarditis have better long-term outcomes than non-fulminant cases (93% vs 45% alive without transplant at 11 years). 4, 5

Arrhythmia Management

For patients with conduction abnormalities:

• Temporary pacemaker insertion is recommended for symptomatic heart block 4
• Permanent pacemaker is indicated for persistent symptomatic sinus node dysfunction or AV block after myocarditis 4
• Ventricular tachyarrhythmias triggered by high-grade AV block require temporary pacing 4

Immunosuppressive Therapy

When NOT to Use Immunosuppression

Immunosuppression is generally NOT indicated for acute lymphocytic myocarditis in adults. 1

The Myocarditis Treatment Trial showed no significant benefit from routine immunosuppression in unselected patients with myocarditis. 6

When to Consider Immunosuppression

Immunosuppressive therapy SHOULD be considered in specific circumstances:

• Giant cell myocarditis - requires aggressive immunosuppression 1, 6, 5
• Cardiac sarcoidosis - benefits from immunosuppressive treatment 1, 5
• Eosinophilic myocarditis - responds to corticosteroids 5
• Autoimmune-mediated myocarditis (systemic lupus erythematosus, other systemic autoimmune disorders) 5
• Biopsy-proven severe myocardial inflammatory infiltrates or fulminant myocarditis unresponsive to conventional therapy 1, 6

Corticosteroid Dosing for Confirmed Myocarditis

When immunosuppression is indicated:

• High-dose methylprednisolone 1 mg/kg IV for at least several days until improvement to grade ≤1 2
• Taper over at least 4-5 weeks after initial improvement 2
• Add additional immunosuppressive agents in severe refractory cases 2

Special Clinical Scenarios

Immune Checkpoint Inhibitor-Associated Myocarditis

For patients developing myocarditis on immunotherapy:

• Permanently discontinue the immune checkpoint inhibitor for grade 3-4 cardiac toxicity 2
• Initiate high-dose corticosteroids immediately (methylprednisolone 1 mg/kg IV) 2
• Mortality remains high at 23% despite rapid treatment, with conduction abnormalities being the primary mode of death 2
• This form is more common with combination anti-CTLA-4/anti-PD-(L)1 therapy and frequently co-occurs with myositis/myasthenia gravis (42% of cases) 2

COVID-19-Associated Myocarditis

Patients with myocarditis and COVID-19 pneumonia requiring supplemental oxygen should be treated with corticosteroids. 1

Pericardial Involvement

Nonsteroidal anti-inflammatory drugs may be used to alleviate chest pain and inflammation in patients with pericardial involvement (myopericarditis). 1

Follow-Up and Long-Term Management

Surveillance Schedule

Follow-up surveillance testing should be performed 3-6 months after presentation to assess recovery of cardiac function and inflammation. 1

This should include:

• Repeat echocardiography or cardiac MRI to assess ventricular function 1
• ECG monitoring for arrhythmias when results will impact management 7
• Reassessment of cardiac biomarkers 1

Long-Term Outcomes

• Approximately 75% of hospitalized patients have an uncomplicated course with near-zero mortality 5
• Dilated cardiomyopathy develops in 21% of patients during long-term follow-up 4
• Patients with acute heart failure or ventricular arrhythmias have a 12% rate of in-hospital mortality or need for transplant 5
• Cardiac transplantation survival rates for myocarditis are similar to other causes of cardiac failure 1

Critical Pitfalls to Avoid

• Do not miss conduction abnormalities - ventricular tachycardia is the most common sustained arrhythmia (76% of arrhythmic cases in pediatric series), and patients with sustained arrhythmias have very high risk of cardiac arrest 4
• Do not delay mechanical support in fulminant cases - early aggressive hemodynamic support improves outcomes 4
• Do not routinely use immunosuppression without specific indications - it has not been shown to benefit typical viral/lymphocytic myocarditis 1, 6
• Do not allow premature return to competitive sports - wait minimum 3-6 months with documented recovery 1
• Do not underestimate immune checkpoint inhibitor myocarditis - it can occur after just 1-2 doses and has high mortality despite treatment 2