What are the latest developments in the diagnosis and treatment of myocarditis (inflammation of the heart muscle)?

From the Guidelines

The latest developments in the diagnosis and treatment of myocarditis prioritize a cause-specific approach, with a focus on supportive care, corticosteroids, and immunosuppressants, as well as the importance of exercise restriction during recovery. The diagnosis of myocarditis has been enhanced by improved diagnostic techniques using cardiac MRI with late gadolinium enhancement and T1/T2 mapping, as outlined in the 2022 ACC Expert Consensus Decision Pathway on Cardiovascular Sequelae of COVID-19 in Adults 1. Treatment advances focus on individualized management based on etiology, severity, and patient characteristics, with viral myocarditis managed through supportive care including ACE inhibitors, beta-blockers, and diuretics for heart failure symptoms. For immune-mediated myocarditis, corticosteroids (typically prednisone) and immunosuppressants like azathioprine or mycophenolate mofetil are increasingly used, as noted in the 2022 ACC Expert Consensus Decision Pathway 1. Key considerations in the management of myocarditis include:

• Hospitalization at an advanced heart failure center for those with definite myocarditis that is either mild or moderate in severity
• Management of fulminant cases with cardiogenic shock, sustained ventricular arrhythmias, and/or advanced atrioventricular block at centers with expertise in advanced heart failure and mechanical circulatory support
• Use of corticosteroids in patients with myocarditis and COVID-19 pneumonia with ongoing need for supplemental oxygen
• Addition of nonsteroidal anti-inflammatory drugs for associated pericardial involvement
• Empiric use of low-dose aldosterone system inhibitors in patients with mildly reduced LV systolic function and stable hemodynamics
• Beta-blockade in patients with supraventricular arrhythmia, if hemodynamically stable, as observed in a small, randomized trial of patients with COVID-19 and acute respiratory distress syndrome requiring mechanical ventilation 1. Exercise restriction during recovery (typically 3-6 months) is also crucial to prevent adverse remodeling, as outlined in the 2022 ACC Expert Consensus Decision Pathway 1. Endomyocardial biopsy remains the gold standard for diagnosis in uncertain cases, while biomarkers like troponin and NT-proBNP help monitor disease activity, as noted in the 2015 ESC Guidelines for the management of patients with ventricular arrhythmias and the prevention of sudden cardiac death 1. These advances reflect growing understanding of myocarditis as a heterogeneous condition requiring individualized management based on etiology, severity, and patient characteristics.

From the Research

Diagnosis of Myocarditis

• 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
• A flexible, multitiered approach to the diagnostic process can help capture the spectrum of myocarditis at an early time-point, allowing for individualized use of diagnostic resources and structured follow-up care once myocarditis is confirmed 5

Treatment 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, 3
• Antiviral agents, such as interferons, pleconaril, and acyclovir, target the causative organism, possibly halting the cascade of myocyte destruction 6
• Natural products of particular interest in the treatment of viral myocarditis are Astragalus membranaceus and Ardisia chinensis 6

Management and Follow-up

• Long-term follow-up should be titrated to the refined risk assessments of patients with a diagnosis of myocarditis and includes arrhythmia monitoring and imaging when the results will likely impact management 5
• Genetic testing should be considered in selected cases, and histologic diagnosis may be considered in nonresponders even at later stages 5
• Approximately 2% to 9% of patients have hemodynamic instability, characterized by inability to maintain adequate end-organ perfusion, and require inotropic agents, or mechanical circulatory devices, such as extracorporeal life support, to facilitate functional recovery 2