Myocarditis

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: ...