Diagnosis

Myocarditis

Findings

T2-weighted 2 chamber long and short-axis images as well as a 10-minute delayed contrast-enhanced phase sensitive inversion recovery image are provided. Cine SSFP images, which are not provided, demonstrated mild hypokinesis of the left ventricle. T2-weighted images demonstrate increased signal within the basal and midinferior and lateral walls.  Late gadolinium enhancement images demonstrate delayed midwall and epicardial enhancement within the midinferior wall of the left ventricle and midwall enhancement within the midlateral wall of the left ventricle.

Discussion

Myocarditis is a diagnosis characterized by inflammatory infiltration of the myocardium with degeneration and/or necrosis of the adjacent myocytes. There are multiple etiologies of myocarditis with the most common being viral and the result of Coxsackie B, adenovirus, parvovirus, Ebstein-Barr virus, and echovirus. Other causes include autoimmune disorders such as Wegener’s granulomatosis, SLE, giant cell arteritis, and Takayasu arteritis.

Myocarditis demonstrates extreme variability in its clinical presentation ranging from asymptomatic to fulminant heart failure. Patients most commonly present acutely with chest pain or fatigue and decreased exercise tolerance. They may have a history of a preceding viral illness or may present with fever and chills. Occasionally arrythmias may also occur. Myocarditis may mimic ischemia on ECG and results in release of cardiac enzymes, such as troponins and creatine kinase. The erythrocyte sedimentation rate also tends to be elevated.

Cardiac MRI is useful in discriminating between myocarditis and cardiac ischemia. Generally cardiac MRI reveals an enlarged heart with diffuse global left ventricular hypokinesis on cine images. T2-weighted images reveal increased signal within the wall of the left ventricle secondary to inflammation. Delayed gadolinium-enhanced images are the most important in diagnosing myocarditis. As opposed to ischemia, which always involves the subendocardium, myocarditis typically affects the subepicardial and mid-wall regions. The inferolateral wall of the left ventricle is most commonly affected.

Treatment of myocarditis depends on the severity of the presentation, but usually consists of exercise avoidance, ECG monitoring, antiarrhythmic drugs in patients with arrhythmias, and treatment of congestive heart failure. Approximately two-thirds of symptomatic patients will recover completely with no clinical sequelae, while the other third will develop a dilated cardiomyopathy.

1. Cummings KW, Bhalla S, Javidan-Nejad C, et al. A pattern-based approach to assessment of delayed enhancement in nonischemic cardiomyopathy at MR imaging. RadioGraphics. 2009;29:89-103.
2. Goitein O, Matetzky S, Beinart R, et al. Acute myocarditis: Noninvasive evaluation with cardiac MRI and transthoracic echocardiography.  AJR Am J Roentgenol. 2009;192:254-258.
3. Laissy JP, Hyafil F, Feldman LJ, et al. Differentiating acute myocardial infarction from myocarditis: Diagnostic value of early- and delayed-perfusion cardiac MR imaging. Radiology. 2005; 237:75-82.