The American College of Cardiology (ACC) published an expert consensus decision pathway that categorizes myocarditis into four stages and outlines diagnostic and management protocols.

The document, published in the Journal of the American College of Cardiology, presents a classification system that defines stages from risk factors through advanced disease.

The staging system classifies myocarditis as:

• Stage A: Patients at risk but without symptoms or evidence of disease
• Stage B: Asymptomatic patients with evidence of myocardial inflammation
• Stage C: Symptomatic myocarditis
• Stage D: Advanced myocarditis with hemodynamic instability requiring intervention

The consensus pathway identifies cardiac magnetic resonance (CMR) imaging and endomyocardial biopsy (EMB) as primary diagnostic tests. CMR diagnosis requires detection of abnormalities in both T1 and T2 imaging. The pathway indicates EMB to diagnose conditions requiring targeted therapies for patients with reduced ventricular function, deranged hemodynamics/symptomatic heart failure, or electrical instability.

The document specifies criteria for referral to advanced heart failure centers with multidisciplinary myocarditis teams, including severely reduced ventricular function, symptomatic heart failure, hemodynamic instability, and electrical instability.

The pathway recommends two cardiac imaging studies for follow-up: an echocardiogram at 2-4 weeks and a second imaging study at 6 months using either echocardiography or CMR based on risk stratification.

The document outlines research needs regarding:

• Disease stage trajectories
• Preventive strategies
• Stage D reversibility factors
• Factors for progression to chronic heart failure

The pathway includes genetic counseling and testing recommendations for consenting patients, citing evidence of genetic predisposition to myocarditis.

Regarding physical activity, the document specifies abstaining from strenuous activity for 3-6 months, with return-to-play determinations based on follow-up CMR, 24-hour arrhythmia monitoring, and exercise testing.

The pathway notes current limitations in healthcare coverage for myocarditis care, particularly for serial imaging studies used in monitoring disease progression and recovery.

The Heart Failure Society of America; the International Society of Cardiomyopathies, Myocarditis and Heart Failure; and the Myocarditis Foundation have endorsed this expert consensus decision pathway.

Potential conflict of interest disclosures can be found in the guidelines.