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—must be hospitalized at an advanced heart failure center, with fulminant cases requiring transfer 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 diffuse T-wave inversion, ST-segment elevation without reciprocal depression, QRS prolongation >120ms (predicts death/transplant), or AV block 1
• High-sensitivity cardiac troponin (elevated in acute myocarditis, though only 34% sensitive in subacute cases) 1
• Transthoracic echocardiogram to assess ventricular function, wall motion abnormalities in non-coronary distribution, and rule out other pathology 1

Cardiology consultation is mandatory for rising troponin and/or ECG or echocardiographic abnormalities concerning for myocarditis. 1

Advanced Imaging

Cardiac MRI is recommended in all hemodynamically stable patients with suspected myocarditis to confirm diagnosis using Lake Louise criteria (epicardial or midwall late gadolinium enhancement, T2 mapping abnormalities). 1 CMR with late gadolinium enhancement is the strongest independent predictor of sudden cardiac death and all-cause mortality. 3

Coronary angiography must be performed to exclude acute coronary syndrome, particularly in patients presenting with chest pain and troponin elevation. 1

Hospitalization and Risk Stratification

Mild to Moderate Myocarditis

• Hospitalize at advanced heart failure center for continuous cardiac monitoring 1, 2
• Approximately 75% have uncomplicated course with 0% mortality 4
• Monitor for arrhythmias, which typically resolve with inflammation resolution 2

Fulminant Myocarditis (Hemodynamic Instability)

• Immediate transfer to center with mechanical circulatory support expertise (ECMO, percutaneous cardiopulmonary support, intra-aortic balloon pump) 1, 2
• Carries 28% mortality at 60 days despite aggressive treatment 2, 4
• Paradoxically better long-term prognosis than non-fulminant forms if acute phase survived 2

Medical Therapy

Guideline-Directed Heart Failure Therapy

Initiate before discharge and continue after discharge:

• 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

Immunosuppression: Limited Indications

Immunosuppression is NOT indicated for typical acute lymphocytic or viral myocarditis. 2, 5

Consider corticosteroids ONLY in these specific scenarios:

• COVID-19 myocarditis with concurrent pneumonia requiring supplemental oxygen 1
• COVID-19 myocarditis with hemodynamic compromise or multisystem inflammatory syndrome 1
• Giant cell myocarditis, cardiac sarcoidosis, or eosinophilic myocarditis 2, 4
• Immune checkpoint inhibitor-induced myocarditis (permanently discontinue immunotherapy and start high-dose methylprednisolone) 2
• Biopsy-proven severe myocardial infiltrates or fulminant myocarditis (balanced against infection risk) 1

Critical Medication Contraindications

NSAIDs are absolutely contraindicated in myocarditis—animal models demonstrate increased inflammation and mortality. 1, 6, 5 NSAIDs may only be used if isolated pericardial involvement is confirmed. 1

Colchicine is reasonable only for documented pericardial involvement, not myocarditis itself. 1

Activity Restriction: Non-Negotiable

Mandate complete exercise abstinence for 3-6 months from diagnosis. 1, 2, 5 This applies to all patients regardless of severity—sudden cardiac death has been reported in athletes after strenuous exertion without prodromic symptoms. 1, 7

Return-to-Play Criteria (After 3-6 Month Abstinence)

Before resuming exercise, require ALL of the following: 1

1. Complete absence of cardiopulmonary symptoms
2. Resolution of laboratory evidence of myocardial injury (normal troponin)
3. Normalization of LV systolic function on echocardiography
4. Absence of spontaneous/inducible arrhythmias on ambulatory monitoring and exercise stress testing

Reassess with repeat CMR at 3-6 months to document resolution of inflammatory findings (LGE and T2 abnormalities). 1 Only 41% of athletes show complete CMR resolution by 8 weeks, and just 1 of 6 with clinical myocarditis had resolution at 10 weeks. 1

Arrhythmia Management

• Acute arrhythmias typically resolve with inflammation resolution; management is supportive 2, 5
• Insert temporary pacemaker for symptomatic or high-grade AV block triggering ventricular tachyarrhythmias 2, 5
• Defer ICD implantation during acute phase to allow LV function recovery; consider wearable cardioverter-defibrillator as bridge 3
• ICD indicated if LVEF remains ≤35% after 3-6 months, similar to nonischemic cardiomyopathy guidelines 3

Follow-Up Surveillance

Perform follow-up testing at 3-6 months including: 2, 5

• Repeat echocardiography or cardiac MRI to assess ventricular function
• Reassessment of cardiac biomarkers
• Ambulatory rhythm monitoring if prior arrhythmias

Long-term risk: 21% develop dilated cardiomyopathy during follow-up, requiring ongoing surveillance. 2, 5

Special Considerations for Underlying Heart Disease

Patients with pre-existing cardiovascular disease and new myocarditis require:

• More aggressive monitoring for decompensation 1
• Earlier consideration of mechanical circulatory support if deterioration occurs 2
• Continuation of baseline cardiac medications unless contraindicated by acute illness 2
• Heightened vigilance for arrhythmias given substrate from both conditions 3

Prognosis note: Patients with normal CMR (normal LV volumes, normal LVEF, no late gadolinium enhancement) have excellent prognosis independent of symptoms, with zero cardiac deaths in long-term follow-up. 8 This underscores the importance of CMR for risk stratification.