Table 2.

Diagnostic test findings in acute myocarditis

Test	Typical Findings	Strengths	Limitations
Cardiac Imaging
CMR	•Typically evaluated using the revised Lake Louise criteria •T2-based criteria for myocardial edema include high native T2 and regional T2 hyperintensity •T1-based criteria for myocardial injury include high native T1, high ECV, and nonischemic pattern LGE •+/− Impaired regional and global ventricular function •+/− Pericardial effusion, edema, and enhancement	•High diagnostic sensitivity and specificity for acute myocarditis •Useful in ruling out other potential diagnoses, such as stress-induced cardiomyopathy •Useful in risk stratification •Useful to demonstrate resolution of edema at follow-up	•Limited availability •Relatively long examination time
Echocardiography	•Impaired regional and global ventricular function •Pericardial effusion •+/− Focal echogenicity •+/− Left ventricular dilatation •+/− Impaired strain	•Widely available •Relatively low cost •Relatively short examination time	•Low sensitivity and specificity for myocarditis •Operator dependent
Cardiac CT	•Pericardial effusion or thickening •+/− Myocardial wall thickening •Late iodine enhancement	•Useful in ruling out other potential diagnoses that might present similarly, such as stress-induced cardiomyopathy	•Exposure to ionizing radiation •Low specificity for acute myocarditis
Cardiac PET	•Focal FDG uptake indicates myocardial inflammation	•Metabolic information •Potentially useful in monitoring treatment response	•Limited availability •Exposure to ionizing radiation
Chest radiography	•Possible cardiomegaly •Pericardial effusion •Pulmonary edema in the setting of heart failure	•Widely available •Low cost •Very short examination time •Useful in ruling out other causes of symptoms	•Findings are not specific for myocarditis
Other Investigations
Troponin	•Elevated values indicate myocyte injury	•Elevated in almost all patients with acute myocarditis •Widely available	•Requires blood draw •Not specific for acute myocarditis
BNP	•Elevated values are associated with heart failure	•Widely available	•Requires blood draw •Not specific for acute myocarditis
ECG	•ST-segment and T-wave abnormalities	•Widely available •Relatively quick •Useful in ruling out other potential diagnoses that might present similarly	•Not specific for acute myocarditis
Endomyocardial biopsy	•Inflammatory infiltrates within the myocardium associated with myocyte damage/necrosis of nonischemic origin •Newer criteria may use immunohistochemical techniques	•Reference standard for definitive diagnosis of myocarditis •High specificity	•Invasive with risk of complications •Low sensitivity for acute myocarditis due to sampling error and patchy disease

Abbreviations: BNP, brain natriuretic peptide; CMR, cardiac magnetic resonance; CT, computed tomography; ECG, echocardiography; ECV, extracellular volume; FDG, fluorodeoxyglucose; LGE, late gadolinium enhancement; PET, positron emission tomography.