Diagnosis
Myocarditis refers to an underlying process that causes inflammation and injury of the heart. It does not refer to inflammation of the heart as a consequence of some other insult. Many secondary causes, such as a heart attack, can lead to inflammation of the myocardium and therefore the diagnosis of myocarditis cannot be made by evidence of inflammation of the myocardium alone.Myocardial inflammation can be suspected on the basis of electrocardiographic (ECG) results, elevated C-reactive protein (CRP) and/or erythrocyte sedimentation rate (ESR), and increased IgM (serology) against viruses known to affect the myocardium. Markers of myocardial damage (troponin or creatine kinase cardiac isoenzymes) are elevated.The ECG findings most commonly seen in myocarditis are diffuse T wave inversions; saddle-shaped ST-segment elevations may be present (these are also seen in pericarditis).The gold standard is the biopsy of the myocardium, in general done in the setting of angiography. A small tissue sample of the endocardium and myocardium is taken and investigated. The cause of the myocarditis can be only identified by a biopsy. Endomyocardial biopsy samples are assessed for histopathology (how the tissue looks like under the microscope): myocardial interstitium may show abundant edema and inflammatory infiltrate, rich in lymphocytes and macrophages. Focal destruction of myocytes explains the myocardial pump failure. In addition samples may be assessed with  immunohistochemistry to determine which types of immune cells are involved in the reaction and how they are distributed. Furthermore, PCR and/or RT-PCR may be performed to identify particular viruses.
Finally, further diagnostic methods like microRNA assays and gene-expression profile may be performed.Cardiac magnetic resonance imaging (cMRI or CMR) has been shown to be very useful in diagnosing myocarditis by visualizing markers for inflammation of the myocardium. Consensus criteria for the diagnosis of myocarditis by CMR were published in 2009. Treatment
While myocarditis has many etiologies and a variable constellation of signs and symptoms, there are few causes that are treatable and thus the main focus is on symptom management. In cases with biopsy-proven myocarditis, the causative cell type can indicate potentially beneficial treatments. These treatments typically consist of corticosteroids, or medications with known benefits in certain autoimmune and systemic conditions. In a majority of cases, the main therapies are used to support patients and are dependent on the severity of symptoms and the time course across which myocarditis develops. Supportive therapies can be divided into two broad categories, medications and mechanical support, since there has yet to be any demonstrated benefits from complementary therapies. Medication
The specific medications that are used to support patients are directly related to the cause of the symptom or sign. Just as the symptoms of myocarditis mirror those of congestive heart failure, so too do the therapies. Additionally, the order in which  therapies are used depends on the degree of heart dysfunction, with stabilization of patient blood pressure and breathing taking highest priority when present.