What is the diagnosis and treatment for myocarditis (inflammation of the heart muscle)?

From the Guidelines

Myocarditis should be managed with hospitalization, ideally at an advanced heart failure center, and treatment should be based on the severity of the condition, with consideration of corticosteroids, nonsteroidal anti-inflammatory drugs, and low-dose colchicine or prednisone for persistent chest pain, as recommended by the 2022 ACC Expert Consensus Decision Pathway 1.

Key Considerations

• The management of myocarditis depends on the severity of the condition, with mild cases resolving on their own with rest and supportive care, and more severe cases requiring hospitalization for monitoring and treatment.
• Treatment should be based on standard pathways unrelated to COVID-19, with consideration of a low-dose aldosterone system inhibitor for patients with mildly reduced LV systolic function and stable hemodynamics, and a beta-blocker for patients with supraventricular arrhythmia, if hemodynamically stable.
• The use of intravenous corticosteroids may be considered in those with suspected or confirmed COVID-19 myocarditis with hemodynamic compromise or MIS-A, as this approach was associated with a favorable prognosis in a small series 1.
• Empiric use of immunosuppressive therapy, such as corticosteroids, may also be considered in those with biopsy evidence of severe myocardial inflammatory infiltrates or fulminant myocarditis, balanced against infection risk.

Important Recommendations

• Patients with cardiogenic shock or hemodynamic instability from suspected myocarditis should be managed similar to other forms of cardiogenic shock at centers with expertise in advanced heart failure, mechanical circulatory support, and other advanced therapies.
• Once a patient with cardiogenic shock or hemodynamic instability from suspected myocarditis has stabilized, CMR should be performed to confirm the diagnosis and assess the extent of ventricular dysfunction and inflammation.
• Guideline-directed medical therapy for heart failure should be initiated before discharge and titrated as appropriate in the outpatient setting.
• Strenuous physical activity should be avoided for 3-6 months, and follow-up surveillance testing, such as ECG, echocardiogram, ambulatory rhythm monitor, and CMR, can be helpful in all patients with myocarditis to gauge recovery of cardiac function and inflammation, guide heart failure management, and assess prognosis 1.

Comparison with Other Guidelines

• The 2015 ESC guidelines for the management of patients with ventricular arrhythmias and the prevention of sudden cardiac death recommend supportive measures, including avoidance of exercise and use of pharmaceutical treatment with neurohormonal blockade with ACE inhibitors and beta-blockers, for patients with fulminant myocarditis 1.
• However, the 2022 ACC Expert Consensus Decision Pathway provides more specific guidance on the management of myocarditis, including the use of corticosteroids and other immunosuppressive therapies, and is therefore considered the most relevant and up-to-date guideline for the management of myocarditis.

From the Research

Definition and Prevalence of Myocarditis

• Myocarditis is defined as a sudden inflammatory injury to the myocardium, affecting approximately 4 to 14 people per 100,000 each year globally 2.
• The condition is associated with a mortality rate of approximately 1% to 7% 2.

Causes of Myocarditis

• The most common causes of myocarditis are viruses, such as influenza and coronavirus; systemic autoimmune disorders, such as systemic lupus erythematosus; drugs, such as immune checkpoint inhibitors; and vaccines, including smallpox and mRNA COVID-19 vaccines 2.

Symptoms and Diagnosis of Myocarditis

• Approximately 82% to 95% of adult patients with acute myocarditis present with chest pain, while 19% to 49% present with dyspnea, and 5% to 7% with syncope 2.
• The diagnosis of myocarditis can be suggested by presenting symptoms, elevated biomarkers such as troponins, electrocardiographic changes of ST segments, and echocardiographic wall motion abnormalities or wall thickening 2.
• Cardiac magnetic resonance imaging or endomyocardial biopsy are required for definitive diagnosis 2, 3, 4.

Treatment and Management of Myocarditis

• Treatment depends on acuity, severity, clinical presentation, and etiology 2.
• Approximately 75% of patients admitted with myocarditis have an uncomplicated course, with a mortality rate of approximately 0% 2.
• Immunosuppression (eg, corticosteroids) is appropriate for patients who have myocarditis characterized by eosinophilic or giant cell myocardial infiltrations or due to systemic autoimmune disorders 2.
• Initial hemodynamic management includes vasopressors and inotropes, whereas more severe cases may require an intra-aortic balloon pump, extracorporeal membrane oxygenation, or a ventricular assist device 5.