Differentiating infarction from myocarditis

Myocarditis can resemble an acute coronary syndrome (ACS), even an ST-segment elevation myocardial infarction. Furthermore, when a coronary angiogram reveals no significant disease, differential diagnosis can be challenging. Endomyocardial biopsy is still the gold standard for the diagnosis of myocarditis; however, its invasive character and limited sensitivity restrict its generalized application to all patients. Both echocardiography and cardiac serum biomarkers may be normal in the setting of ACS or myocarditis, and when abnormal lack enough specificity to differentiate reliably between the two entities. Nuclear techniques have high sensitivity but modest specificity for the detection of myocarditis, and have the additional limitations of availability and radiation exposure. Cardiac magnetic resonance (CMR) has emerged as a leading modality in the noninvasive diagnosis of myocarditis due to its ability to detect myocardial edema, hyperemia, necrosis and fibrosis in a safe and reproducible fashion. In patients with an ACS-like presentation but normal coronary arteries, CMR is useful not only to differentiate acute myocarditis from an ischemic event but also to identify alternative etiologies. L Heart Metab; 2014;62:13–17