Approach Considerations
Echocardiography
Echocardiography is critical in making the diagnosis of myocarditis. Typically, the presence of diminished ventricular function with dilatation of one or several chambers of the heart becomes obvious. Echocardiography aids in ruling out pericardial effusion or structural congenital heart disease as the etiology of the symptoms. [16]
Cardiac magnetic resonance imaging (CMRI)
CMRI is noninvasive and can aid not only in the diagnosis of myocarditis but also for monitoring of disease progression. [3, 4, 9] This imaging modality can also clarify the presence of inflammation or fibrosis, function, and pericardial effusion, but it is not a substitute for endomyocardial biopsy for determining the etiology of myocarditis. [17]
Electrocardiography
Sinus tachycardia out of proportion to the degree of fever may be noticeable in patients with myocarditis. Arrhythmias and ST-T wave changes in as many as 80% of patients, may be associated with myocarditis. These changes may be sensitive indicators of myocardial ischemia, or they may be nonspecific findings.
Histologic findings
The major purposes of a tissue biopsy are to establish a diagnosis of myocarditis and to classify the stage of disease as acute, healed, or chronic. The specific histologic findings differ based on the particular etiologic agent associated with myocarditis.
Endomyocardial Biopsy
The role of endomyocardial biopsy in the diagnosis of myocarditis remains controversial. Biopsy may present somewhat of a risk in the acutely ill and unstable patient, and a histologic diagnosis may not be easy.
The Heart Failure Society of America recommends consideration of endomyocardial biopsy in patients with an acute deterioration of cardiac function of unknown etiology who are unresponsive to medical therapy, [1] and the European Society of Cardiology indicates performing endomyocardial biopsy in those with clinically suspected myocarditis after ischemia has been ruled out with coronary angiography [9]
Typical sampling usually includes small areas of the right ventricle (septal area). Because myocarditis may be focal and may primarily involve the left ventricle, results of the sampling techniques used may not fully represent the true incidence of myocarditis. That is, a negative biopsy result does not rule out myocarditis.
A major problem with endomyocardial biopsy is the possibility of overinterpretation or misinterpretation of the biopsy specimen. In addition, some clinicians argue that the results of endomyocardial biopsy may not change the treatment of myocarditis. This may be true, at least until a clearer role emerges for immunosuppression therapy in patients with this disease. Little work in pediatric patients has been done in this area.
The high-contrast and high-resolution fluorescent imaging of confocal laser scanning microscopy and super-resolution microscopy may potentially increase the diagnostic yield of endomyocardial biopsy. [18] These modalities appear to provide improved quantitative digital analysis and may thereby improve precision and accuracy in the evaluation of critical pathologic features. [18]
Performing a biopsy to establish a subset of pediatric patients with active myocarditis may be useful in order to study different therapies in a controlled, prospective manner.
-
Pediatric nonviral myocarditis. This image is reveals myocarditis with scarring at autopsy. It is a short-axis gross photograph from an 8-year-old child who had clinical myocarditis, showing scarring of both ventricles, more prominent in the left. The fibrosis depicts a random distribution with epicardial, myocardial, and pericardial involvement.
