Myocarditis

Myocarditis may present with a wide range of symptoms, ranging
from mild dyspnea or chest pain that resolves without specific therapy
to cardiogenic shock and death. Dilated cardiomyopathy withchronic heart
failure is the major long-term sequela of myocarditis. Most often, myocarditis results
from common viral infections; less commonly, specific forms of myocarditis may
result from otherpathogens, toxic or hypersensitivity drug reactions, giant-cell myocarditis,
or sarcoidosis. The prognosis and treatment of myocarditis vary according
to the cause, and clinical and hemodynamic datausually provide guidance to decide
when to refer a patient to a specialist for endomyocardial biopsy. The aim of this
review is to provide a practical and current approach to the evaluation andtreatment
of suspected myocarditis.
Definition
The standard Dallas pathological criteria for the definition of myocarditis require
that an inflammatory cellular infiltrate with or without associatedmyocyte necrosis
be present on conventionally stained heart-tissue sections (Fig. 1A).1 These criteria
are limited by variability in interpretation, lack of prognostic value, and low sensitivity,
inpart due to sampling error.2,3 These limitations have led to alternative
pathological classifications with criteria that rely on cell-specific immunoperoxidase
stains for surface antigens, such asanti-CD3, anti-CD4, anti-CD20, anti-CD68, and
anti–human leukocyte antigen (Fig. 1B).4,5 Criteria that are based on immunoperoxidase
staining have greater sensitivity and may have prognostic value.6Preliminary studies suggest that noninvasive cardiac magnetic resonance imaging
(MRI) may provide an alternative method for diagnosis without the risks of
biopsy. For example, regions ofmyocarditis are reported to correlate closely with
regions of abnormal signal on cardiac MRI.7,8 The lack of consensus regarding the
value of invasive studies such as endomyocardial biopsy and the overall...