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KEY FEATURES

ESSENTIALS OF DIAGNOSIS

  • New ventricular dysfunction with an antecedent viral syndrome

  • Elevated erythrocyte sedimentation rate and/or cardiac biomarkers with acute myocarditis

  • ECG shows sinus tachycardia, nonspecific ST-T changes, atrial or ventricular arrhythmias, or conduction abnormalities

  • Echocardiogram demonstrates chamber enlargement and globally reduced left ventricular (LV) contractility, sometimes with regional variations

  • Mural thrombi may be present

GENERAL CONSIDERATIONS

  • Myocardial inflammation and secondary immune response leading to cardiac injury and ventricular dysfunction

  • Can present as fulminant, acute, chronic active, and chronic persistent with variable natural histories

  • Focal or diffuse myocardial inflammation that may also involve the endocardium, pericardium, or valvular structures

  • Most commonly initiated by viral infection, although may occur as a result of other infectious organisms, drugs, toxins, collagen vascular diseases, or autoimmune or hypersensitivity reactions

  • Most common viral causes in the United States are parvovirus, adenovirus, and enteroviruses. Other viruses include Coxsackie B echovirus, influenza, hepatitis C, and cytomegalovirus

  • Routine endomyocardial biopsy not recommended because inflammatory changes are often focal and nonspecific. Endomyocardial biopsy can be useful when giant cell myocarditis, fulminant lymphocytic myocarditis, or cardiac sarcoidosis is suspected

  • When positive, the inflammatory changes include inflammatory infiltrate with adjacent myocyte injury

CLINICAL PRESENTATION

SYMPTOMS AND SIGNS

  • Clinical presentation is variable

  • Most commonly asymptomatic

  • Symptomatic patients may describe an antecedent viral syndrome, including fever, malaise, fatigue, arthralgias, myalgias, and skin rash

  • Chest pain (pleuritic, ischemic, or atypical) is common

  • Dyspnea, fatigue, decreased exercise tolerance

  • Palpitations, dizziness, or syncope

  • Cardiogenic shock

PHYSICAL EXAM FINDINGS

  • Exam findings vary widely

  • Tachycardia (rarely, bradycardia)

  • Hypotension

  • Fever

  • Signs of fluid overload

  • Murmurs of mitral or tricuspid regurgitation (diastolic murmurs are rare)

  • S3 and occasionally S4 gallops

  • Pleural rubs and pericardial friction

  • Circulatory collapse and shock (rare)

DIFFERENTIAL DIAGNOSIS

  • Acute myocardial ischemia or infarction due to coronary artery disease

  • Pneumonia

  • Congestive heart failure due to other causes

DIAGNOSTIC EVALUATION

LABORATORY TESTS

  • Elevated erythrocyte sedimentation rate

  • Elevated cardiac troponin seen in some patients

ELECTROCARDIOGRAPHY

  • May be normal, but more commonly, there are nonspecific changes

  • Atrial or ventricular ectopic beats

  • Atrial tachycardia or fibrillation

  • Atrioventricular block or interventricular conduction block (eg, left bundle branch block)

  • Regional ST elevations and Q waves that mimic acute myocardial infarction or diffuse ST elevations that simulate pericarditis

IMAGING STUDIES

  • Chest x-ray: may be normal or demonstrate cardiomegaly with or without pulmonary edema

  • Echocardiography: LV enlargement; globally reduced LV contractility, sometimes with regional variation mimicking myocardial infarction; increased LV wall thickness due to edematous inflammation occasionally in early disease; mural thrombi

  • Cardiac MRI can be useful in detecting areas of inflammation

DIAGNOSTIC PROCEDURES

  • Cardiac catheterization: ...

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