IS Case 103: Myocarditis
Imaging Sciences URMC 2008
Publication Date: 2009-05-20
Delayed post-gadolinium (Gd) contrast enhanced short-axis T1-weighted images show focal delayed enhancement in the anterolateral LV myocardium extending from the base to mid myocardium. The enhancement spares portions of the endocardium. There is also patchy enhancement in the inferolateral region near the outflow tract.
Myocarditis is an acute injury to the myocardium, usually due to viral infections. Clinical manifestations include fever and chest pain, or occasionally heart failure. Accurate diagnosis is essential as the disease can progress to chronic myocarditis and dilated cardiomyopathy. In the early stages, myocarditis is a focal process in the myocardium. Cardiac MRI is an excellent method to identify myocardial edema and myocyte damage non-invasively. In addition since myocarditis can mimic myocardial infarction (MI) clinically, first-pass perfusion and delayed-enhancement images may help to differentiate the two. Delayed enhancement found in myocarditis is due to increased capillary permeability from inflammation and acute cell damage which induces intracellular diffusion of Gd, which corresponds to the histologic features of interstitial edema and lymphocyte infiltration with myocyte necrosis. The enhancement is typically inferolateral and subepicardial in a nonvascular distribution. In contradistinction, MI shows subendocardial or transmural delayed enhancement in a vascular distribution. Early acute myocarditis typically progresses from a focal nodular form to a diffuse pattern of enhancement in the span of about 1 to 2 weeks. Identification of peripheral skeletal enhancement in the acute phase may be helpful in the diagnosis as myocarditis is thought to belong to a generalized infectious state of skeletal muscle. Identification of skeletal muscle involvement may allow for diagnosis by peripheral muscle biopsy instead of the gold-standard of endomyocardial biopsy.
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