Table 1.

Clinical classifications of myocarditis.

Causative criteria	Histological criteria	Clinicopathological criteria
Virus: coxsackievirus B3, adenoviruses or herpesviruses and other	Active myocarditis: cardiac inflammation with apparent cardiomyocyte necrosis	Fulminant myocarditis: sudden onset, severe heart failure, cardiogenic shock or life-threatening arrhythmias
Protozoa: Trypanosoma cruzi (Chagas disease)	Borderline myocarditis: cardiac inflammation without evident cardiomyocyte necrosis	Acute myocarditis: highly variable from asymptomatic to cardiogenic shock, ventricular dysfunction, may progress to dilated cardiomyopathy
Bacteria: Borrelia burgdorferi (Lyme disease) and other	Lymphocytic myocarditis: extensive infiltration of lymphocytes and monocytes	Chronic active myocarditis: variable clinical symptoms, ventricular dysfunction, relapses of clinical symptoms and chronic myocardial inflammation on histology
Immune checkpoint inhibitors: anti-CTLA-4, anti-PD-1 or anti-PD-L1 therapy	Giant cell myocarditis: multinucleated giant cells and lymphocytes on heart biopsies	Chronic persistent myocarditis: persistent histologic infiltrate with myocyte necrosis, chest pain or palpitation without ventricular dysfunction
Systemic autoimmune diseases: Systemic lupus erythematosus, myasthenia gravis and other	Eosinophilic myocarditis: eosinophil-rich infiltrates with extensive myocyte necrosis