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  1. What are the most common etiologies of pericarditis and myocarditis?

  2. How are pericarditis and myocarditis diagnosed?

  3. Which imaging modality is most accurate in diagnosing myocarditis?

  4. What are the evidence-based physical examination, radiographic, electrocardiographic, and imaging findings used in the diagnosis of cardiac tamponade, and how is it managed?

  5. What are the differences in physical examination, testing results, and treatment of constrictive pericarditis versus cardiac tamponade?

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Introduction

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Acute myocarditis is an inflammatory infiltration of the myocardium. The clinical sequelae of this disease include subclinical disease to fulminant cardiogenic shock.

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Acute myocarditis can present a challenging diagnostic dilemma. Traditionally, the diagnosis of myocarditis is made by endomyocardial biopsy. In acute myocarditis, biopsy shows areas of necrosis with a lymphocytic infiltration. However, endomyocardial biopsy is subject to procedural risks, sampling bias, and poor sensitivity. Noninvasive cardiac magnetic resonance imaging (MRI) has become an alternative mechanism for diagnosing myocarditis.

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Pathophysiology

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The most common cause of myocarditis is a viral pathogen. However, other infectious, autoimmune, and toxic causes occur as well. Initial studies in the latter half of the 20th century indicated Coxsackie B virus as the frequent causative agent in endomyocardial biopsies. However, since the 1990s adenovirus has emerged as the more frequent viral agent. Since that time, parvovirus and other viruses have been seen in the biopsy results of patients with myocarditis. Other viral causes of acute myocarditis have been reported in patients with hepatitis C virus (HCV), Epstein-Barr virus, and cytomegalovirus (CMV).

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Infectious etiologies other than viruses have been implicated as a cause of myocarditis, including mycoplasma and Borrelia burgdorferi (Lyme disease). In developing countries, Trypanosoma cruzi has been known to infect the myocardium causing Chagas disease.

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Presentation

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The clinical presentation of patients with myocarditis can range from mild dyspnea and chest discomfort to fulminant cardiogenic shock. Patients may report a viral prodrome in the weeks preceding presentation, including fevers, respiratory, or GI symptoms. According to the European Study of Epidemiology and Treatment of Inflammatory Heart Disease, patients with myocarditis present with dyspnea (72%), chest pain (32%), and arrhythmias (18%). Patients may also present with symptoms related to congestive heart failure, including fatigue, orthopnea, paroxysmal nocturnal dyspnea, palpitations, and syncope.

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As an infiltrative process, the amount of affected myocardium can be highly variable in myocarditis. Some patients may present with ventricular arrhythmias if the conducting system is involved while other patients may present with a dilated cardiomyopathy.

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The physical examination of patients with acute myocarditis may correlate with the patients' symptoms. In patients with mild symptoms, the physical examination may be relatively normal. However, patients with severe myocarditis may appear in cardiogenic shock. Diaphoresis, rales, jugular venous distention, hypotension, and peripheral edema can all be seen in patients with myocarditis.

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Diagnosis

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The electrocardiogram (ECG) in myocarditis may show sinus ...

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