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.
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