In 111-antimyosin antibody can be used to identify myocarditis [14]. MRI Chest There is no relevant literature to support the use of MRI chest for the evaluation of inflammatory myocardial disorders. MRI Heart Function and Morphology In acute myocarditis, MRI is performed in patients with symptoms of myocarditis, evidence of myocardial injury, and suspected viral etiology. MRI has been shown to have an impact on making a decision in >50% of patients and provides a new diagnosis in 11% of patients [115]. One study showed that using MRI at a lower threshold in patients with MINOCA (ie, using MRI independent of clinical likelihood of myocarditis) led to a 6.3-fold increase in the incidence of myocarditis with doubling of MRIs positive for myocarditis, indicating that myocarditis is currently an underdiagnosed entity [137]. MRI shows functional abnormalities (global systolic dysfunction or focal wall motion abnormalities), capillary hyperemia (high signal in EGE), edema (high signal in T2-weighted images, high native T1 and T2 values, increased ECV), necrosis/fibrosis (LGE in mid myocardial/subepicardial; high T1 and ECV), and pericardial effusion. The Lake Louise criteria, which were used in the diagnosis of acute myocarditis, required two out of the three criteria (edema, EGE, and/or LGE) to be positive [138]. A combination of all three is required if high positive predictive value is desired (positive likelihood ratio of 7.7, accuracy of 80%, specificity of 90%, sensitivity of 77%, positive predictive value of 96%, and negative predictive value of 53%), whereas T2 or LGE criteria are adequate for high sensitivity (91% sensitivity, 84% accuracy) [138]. Removing EGE as a criterion does not change the accuracy (80% with, 84% without) but reduces sensitivity (90% with, 60% without) [138].
Nonischemic Myocardial Disease with Clinical Manifestations Ischemic Cardiomyopathy Already Excluded . In 111-antimyosin antibody can be used to identify myocarditis [14]. MRI Chest There is no relevant literature to support the use of MRI chest for the evaluation of inflammatory myocardial disorders. MRI Heart Function and Morphology In acute myocarditis, MRI is performed in patients with symptoms of myocarditis, evidence of myocardial injury, and suspected viral etiology. MRI has been shown to have an impact on making a decision in >50% of patients and provides a new diagnosis in 11% of patients [115]. One study showed that using MRI at a lower threshold in patients with MINOCA (ie, using MRI independent of clinical likelihood of myocarditis) led to a 6.3-fold increase in the incidence of myocarditis with doubling of MRIs positive for myocarditis, indicating that myocarditis is currently an underdiagnosed entity [137]. MRI shows functional abnormalities (global systolic dysfunction or focal wall motion abnormalities), capillary hyperemia (high signal in EGE), edema (high signal in T2-weighted images, high native T1 and T2 values, increased ECV), necrosis/fibrosis (LGE in mid myocardial/subepicardial; high T1 and ECV), and pericardial effusion. The Lake Louise criteria, which were used in the diagnosis of acute myocarditis, required two out of the three criteria (edema, EGE, and/or LGE) to be positive [138]. A combination of all three is required if high positive predictive value is desired (positive likelihood ratio of 7.7, accuracy of 80%, specificity of 90%, sensitivity of 77%, positive predictive value of 96%, and negative predictive value of 53%), whereas T2 or LGE criteria are adequate for high sensitivity (91% sensitivity, 84% accuracy) [138]. Removing EGE as a criterion does not change the accuracy (80% with, 84% without) but reduces sensitivity (90% with, 60% without) [138].