Equine pericarditis is the inflammation (swelling and irritation) of the horse's pericardium (a fibrous tissue that surrounds and protects the heart). The condition can present as acute (sudden and short-lived) and chronic (persistent over long periods).

Equine pericarditis can be idiopathic or it can be the result of a viral or bacterial infection, trauma, tumor, or immune-mediated condition. Clinical signs vary depending on the severity, cause, age of the horse, and overall health.