cardiovascular disorders
Myocarditis
Diagnosis of Myocarditis
Electrocardiography (ECG) and cardiac enzymes Cardiac imaging Sometimes, endomyocardial biopsy Tests to identify cause Myocarditis should be suspected when otherwise healthy patients with no cardiac risk factors present with symptoms of heart failure or arrhythmias. ECG, cardiac enzymes, and cardiac imaging are not specific for myocarditis but can be diagnostic in the appropriate clinical setting. can be normal or abnormal in patients with myocarditis. ST segment abnormalities are common and can mimic myocardial ischemia. ST segment elevation is sometimes seen but more common findings include nonspecific ST-T wave changes. Patients may experience conduction delays and atrial or ventricular arrhythmias, including sinus tachycardia, Ventricular Tachycardia (VT) , and Cardiac enzymescan be abnormal in patients with acute myocarditis. Cardiac troponin and CK-MB (creatine kinase muscle band isoenzyme) can both be elevated due to necrosis of cardiac myocytes. Cardiac imagingcan be abnormal in patients with myocarditis. Echocardiogram can be normal in early or mild myocarditis, but segmental wall motion abnormalities (mimicking myocardial ischemia) can be seen. Left ventricular dilation and systolic dysfunction can also be seen as in dilated cardiomyopathy. Diastolic relaxation parameters are often abnormal on echocardiography. Cardiac MRI is becoming increasingly important in the diagnosis of myocarditis. Cardiac MRI of patients with myocarditis may show a characteristic pattern of late gadolinium enhancement in the subepicardial and mid-myocardial walls (in contrast to ischemia where late gadolinium enhancement is usually subendocardial with extension to mid-myocardial and epicardial walls). Other diagnostic features of myocarditis on cardiac MRI are the presence of myocardial edema and myocardial hyperemia relative to skeletal muscle. Endomyocardial biopsyshowing inflammatory infiltrate of the myocardium with necrosis of adjacent myocytes is the gold standard for diagnosis of myocarditis. However, this test has low sensitivity for diagnosis for myocarditis due to sampling error. Therefore, a positive biopsy result is diagnostic for myocarditis, but a negative result does not rule it out. In addition, the biopsy carries a risk of complications, including myocardial rupture and death, so is not routinely done. Endomyocardial biopsy should be done in cases of fulminant heart failure, ventricular arrhythmias, or heart block or if results would affect management (eg, if there is suspicion for giant cell myocarditis where prompt treatment can decrease mortality rates). After myocarditis is diagnosed, tests to determine etiology are done. In a young, previously healthy adult who presents with symptoms of a viral infection and myocarditis, an extensive evaluation is usually unnecessary. Differentiating viral from idiopathic myocarditis is difficult, expensive, and generally of little practical importance. A complete blood count (CBC) is helpful to assess for peripheral eosinophilia, which is present in hypersensitivity myocarditis. Cardiac Catheterization may be useful for ruling out ischemia since myocarditis can mimic In other cases, a biopsy of myocardial tissue may be needed to establish a diagnosis. Acid-fast stains of myocardial tissue are essential if tuberculosis (TB) is considered possible (TB myocarditis can be aggressive and can worsen rapidly with corticosteroid therapy). Myocardial samples are examined for giant cells, which are characteristic of giant cell myocarditis, and the granulomas that occur in sarcoidosis. Other tests include acute-phase reactants, routine chemistry tests, cultures, autoimmune tests, and, when appropriate, tests for HIV, COVID-19 , histoplasmosis complement fixation or Lyme disease titers (in endemic areas), and antibody tests for coxsackievirus, influenza virus, and streptococcus. 