Table 1.

Centers for Disease Control and Prevention working case definitions for acute myocarditis and acute pericarditis

CDC Working Case Definitions
Acute Myocarditis		Acute Pericarditis
Confirmed Case	Probable Case	Probable Case
Presence of ≥ 1 new or worsening of the following clinical symptomsa • Chest pain/pressure/discomfort • Dyspnea/shortness of breath • Palpitations • Syncope AND ≥ 1 of the following • Histopathologic confirmation of myocarditis • Elevated troponin greater than upper limit of normal and CMR findings consistent with myocarditisb AND • No other identifiable cause of the symptoms and findings	Presence of ≥ 1 new or worsening of the following clinical symptomsa • Chest pain/pressure/discomfort • Dyspnea/shortness of breath • Palpitations • Syncope AND ≥ 1 new finding of • Elevated troponin • ECG consistent with myocarditisc • Abnormal function or wall motion abnormality on echocardiography • CMR consistent with myocarditisb AND • No other identifiable cause of the symptoms and findings	Presence of ≥ 2 new or worsening of the following clinical symptoms • Acute chest pain (typically described as pain made worse by lying down, deep inspiration, cough, and relieved by sitting up or leaning forward, although other types of chest pain may occur) • Pericarditis rub on examination • New ST-elevation or PR-depression on ECG • New or worsening pericardial effusion on echocardiogram or CMR OR • Autopsy cases may be classified as pericarditis based on meeting histopathologic criteria of the pericardium

^aClinical symptoms are for adolescents and adults. Infants and children younger than 12 years night instead have greater than or equal to 2 of the following symptoms: irritability, vomiting, poor feeding, tachypnea, and lethargy. Individuals who lack the listed symptoms but who meet other criteria may be classified as subclinical myocarditis (probable or confirmed).

^bUsing the Lake Lousie criteria.

^cTo meet the ECG or rhythm monitoring criterion, a probable case must include at least one of the following: (1) ST-segment or T-wave abnormailities; (2) paroxysmal or sustained atrail, superventricular, or ventricular arrhythmias; or (3) AV nodal conduction delays or intraventricular conduction defects.

Adapted from Gargano JW, Wallace M, Hadler SC, et al. Use of mRNA COVID-19 Vaccine After Reports of Myocarditis Among Vaccine Recipients: Update from the Advisory Committee on Immunization Practices — United States, June 2021. MMWR Morb Mortal Wkly Rep 2021;70:977–982; and from Bozkurt B., Kamat I. and Hotez P.J., Myocarditis with COVID-19 mRNA vaccines, Circulation, 144 (6), 2021, 471–484.