The American College of Cardiology (ACC) has recently released guidance for diagnosing and treating acute myocarditis in adult patients. The 2024 ACC Expert Consensus Decision Pathway (ECDP) on Strategies and Criteria for the Diagnosis and Management of Myocarditis outlines a 5-step care pathway, along with recommendations for resuming strenuous physical activity. Additionally, the guidelines aim to bridge knowledge gaps and identify areas for future research in the field of myocarditis management. This important document was published on December 10, 2024.

The ACC’s ECDP on myocarditis in adult patients offers a structured decision-making framework that integrates the most recent advancements in clinical practice. In this discussion, we will delve into the key insights and recommendations provided. Please note that this overview does not encompass all major points. For a detailed list of recommendations, please refer to the summary provided or access the complete guideline document. Let us begin!

Key Takeaways and Recommendations

A brief overview of ACC’s 5-step pathway for diagnosing and managing myocarditis, along with key points:

  1. Recognition of Symptoms: 
    • Clinicians across various healthcare settings (e.g., primary care, cardiology, emergency departments) should consider myocarditis in patients presenting with diverse symptoms. Early recognition is essential. Key symptoms to watch for include chest pain, heart failure (HF)/shock, and arrhythmia-related symptoms (e.g., presyncope, syncope). In younger individuals, a history of a recent viral infection or other risk factors for myocarditis, followed by any of these cardiovascular symptoms, should raise suspicion for this diagnosis.
  2. Initial Screening and Evaluation
    • Once myocarditis is suspected, essential diagnostic tests should be conducted, including an ECG, complete blood count (CBC), biomarkers (hs-cTn, CRP, natriuretic peptides), and an echocardiogram. Coronary artery disease must be excluded with coronary angiography if clinically indicated. Triage decisions should include determining whether hospitalization, advanced care, or circulatory support is needed based on the patient’s condition. High-sensitivity cardiac troponin (hs-cTn) is commonly used in diagnosis, though some myocarditis cases may not show elevated hs-cTn levels. Further research is needed to establish the role of normal hs-cTn levels in ruling out myocarditis, as well as the prognostic value of serial measurements.
  3. Confirmatory Tests: 
    • If the patient is stable, two key tests are considered for diagnosis: Cardiac MRI (CMR) and, when necessary, endomyocardial biopsy (EMB). CMR can noninvasively assess cardiac inflammation and is particularly useful in diagnosing symptomatic myocarditis. CMR findings are based on abnormal T1 and T2 imaging. However, in cases with reduced ventricular function, hemodynamic instability, or electrical instability, an EMB may be required to identify the specific type of myocarditis (e.g., giant cell, eosinophilic, sarcoidosis) and guide targeted therapies such as immunosuppressive treatment.
  4. Treatment Initiation: 
    • Once myocarditis is confirmed or strongly suspected, pharmacological treatment should be initiated. In cases of clinical instability, temporary circulatory support may be necessary. For patients whose condition worsens, long-term options such as a left ventricular assist device (LVAD) or heart transplantation should be considered. Risk stratification is important in guiding treatment decisions, with patients exhibiting severe ventricular dysfunction, symptomatic heart failure, hemodynamic instability, or electrical instability referred to advanced heart failure centers with multidisciplinary myocarditis teams.
  5. Follow-up and Long-Term Care: 
    • Even after symptoms resolve, ongoing monitoring is essential. This includes repeat biomarker assessments, echocardiograms, and follow-up CMRs. A reassessment of physical activity, including return to competitive sports, should be performed 3-6 months after diagnosis. Long-term follow-up involves two key imaging studies: an early echocardiogram (2-4 weeks post-diagnosis) to monitor left ventricular function, and a second follow-up (echocardiogram for low-risk myocarditis or CMR for higher-risk cases) around 6 months. Advocacy for insurance coverage of these tests is recommended. Additionally, genetic counseling and testing should be offered to eligible patients.

In addition to establishing a clear pathway for the diagnosis and management of myocarditis, the ACC underscores the necessity for further research in various areas. Key research priorities include:

  • Impact of Social Determinants: Investigating how factors like socioeconomic status, access to healthcare, and other social determinants affect the development and progression of myocarditis.
  • International Registries: Establishing global registries with diverse stakeholder involvement to gather comprehensive data on myocarditis.
  • Improved Diagnostic Techniques: Advancing phenotyping through novel biomarkers, imaging methods, and refined pathological interpretation of endomyocardial biopsy (EMB) specimens, including the role of viral polymerase chain reaction (PCR) testing.
  • Immunosuppression Efficacy: Assessing the benefits of immunosuppressive treatment for lymphocytic myocarditis through large, prospective randomized clinical trials.
  • Extracorporeal Membrane Oxygenation (ECMO): Exploring whether unloading the left ventricle in patients on ECMO improves outcomes.
  • Psychological Impact: Gaining a better understanding of the psychological burden on both patients and caregivers following a myocarditis episode.

These research areas are crucial for enhancing the comprehension, treatment, and long-term care of patients with myocarditis. We eagerly anticipate further updates from the ACC, which will undoubtedly encompass advancements in this field.  

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