Snapshot A 26-year-old man presents to his primary care physician due to shortness of breath and mild palpitations. He reports that his symptoms have progressively worsened over the course of a month. His shortness of breath is most apparent with climbing the stairs or low-intensity jogging. Approximately 2 months ago, he experienced an upper respiratory infection. Physical examination is unremarkable. An electrocardiogram demonstrates nonspecific cardiac abnormalities and cardiac biomarkers and chest radiograph are unremarkable. Preparations are made to obtain a cardiac echocardiogram. Introduction Clinical definition inflammation of the myocardium that results in myocardial necrosis and degeneration Etiology Infectious viruses coxsackievirus B HIV adenovirus parvovirus B19 HHV-6 parasitic Toxoplasma gondii Trichinella spiralis bacterial Borrelia burgdorferi (Lyme disease) Mycoplasma pneumoniae Corynebacterium diphtheriae toxins carbon monoxide black widow venom medications doxorubicin autoimmune disease Kawasaki disease sarcoidosis systemic lupus erythematosus polymyositis/dermatomyositis Pathophysiology in active cases, there is an interstitial inflammatory infiltration of lymphocytic cells in the myocardium this is associated with myocyte necrosis Presentation Symptoms/physical exam the clinical presentation is broad asymptomatic heart failure findings e.g., dyspnea on exertion, fatigability, and volume overload arrhythmia findings e.g., palpitations and lightheadedness chest pain fever Differential Acute coronary syndrome differentiating factors ECG changes (NSTEMI and STEMI) with increased biomarkers (cardiac troponins) DIAGNOSIS Making the diagnosis based on clinical presentation and a number of diagnostic tests (e.g., ECG, serum biomarkers, and cardiac imaging) biopsy (most accurate test) showing myocardial necrosis Treatment Treatment is directed at the underlying cause of myocarditis Complications Dilated cardiomyopathy Heart failure Sudden cardiac death