New ACC Guidance Introduces Four-Stage Framework for Diagnosing and Managing Myocarditis

In updated recommendations published in the Journal of the American College of Cardiology, the American College of Cardiology (ACC) has outlined a new expert consensus decision pathway for the diagnosis and management of acute myocarditis. Led by Mark H. Drazner, M.D., from the University of Texas Southwestern Medical Center, the guidance incorporates recent advancements in clinical practice and offers a structured approach to addressing this complex condition in adult patients.

A Four-Stage Classification of Myocarditis

The guidance introduces a four-stage framework for categorizing myocarditis based on disease progression:

• Stage A: Risk factors or exposure to conditions associated with myocarditis.
• Stage B: Evidence of myocardial inflammation in asymptomatic individuals.
• Stage C: Symptomatic myocarditis, which may present as chest pain, heart failure, or arrhythmias.
• Stage D: Advanced myocarditis, often characterized by severe functional impairment or shock.

While the framework offers a practical tool for clinicians, the authors note that further research is needed to clarify the trajectories of these stages and their risk of progression to chronic heart failure. Diagnostic tools such as cardiac magnetic resonance imaging and endomyocardial biopsy remain pivotal in identifying myocarditis, particularly in patients without elevated high-sensitivity cardiac troponin (hs-cTn) levels.

Why the New Guidance Matters

For patients with symptomatic myocarditis, risk stratification is essential for determining whether referral to an advanced heart failure center with a multidisciplinary team is warranted. The ACC emphasizes that follow-up care should not end after two to three weeks, even if symptoms resolve. Instead, longitudinal management should include two cardiac imaging studies—one conducted early after diagnosis and another at six months.

The guidance also includes a four-step care pathway for managing myocarditis: triaging the patient, obtaining pivotal diagnostic tests, providing appropriate therapies, and implementing ongoing follow-up care. By consolidating recent evidence, this structured approach aims to improve clinical outcomes and standardize care for a condition that can present with significant diagnostic and therapeutic challenges.

By offering clear, stage-based recommendations, the ACC's guidance seeks to assist clinicians in navigating the complexities of myocarditis and enhance the overall quality of patient care.