Seaport Criteria Bring Clarity to Myocarditis Grading

Seaport criteria classify lymphocytic myocarditis into mild, moderate, and severe grades.

Diagnosis is based on T lymphocyte identification using CD3 immunohistochemistry.

Mild myocarditis requires either a single cluster of 5+ lymphocytes or 15 non-clustered CD3+ cells.

Moderate myocarditis requires two or more lymphocyte clusters.

Severe myocarditis shows multifocal or diffuse infiltrates with myocyte injury.

Developed through a 3-year Delphi process involving pathologist feedback.