cardiovascular disorders
Myocarditis
Etiology of Myocarditis
Myocarditis may result from infectious or noninfectious causes. Many cases are idiopathic (see table Causes of Myocarditis ). is most often viral in the US and other high income nations. The most common viral causes in the US are parvovirus B19 and Overview of Herpesvirus Infections . In lower income nations, infectious myocarditis is most often associated with Noninfectious causesinclude cardiotoxins, certain drugs, and some systemic disorders. Myocarditis caused by drugs is termed hypersensitivity myocarditis. Myocarditis after mRNA-based COVID-19 vaccination is rare and far less common than COVID-associated myocarditis It occurs mostly in adolescent and young adult males, usually within a week of vaccination, and is generally mild. Giant cell myocarditis is a rare form of myocarditis with a fulminant course. The etiology is unclear but may include an autoimmune mechanism. Biopsy shows characteristic multinucleated giant cells. Patients with giant cell myocarditis present in cardiogenic shock and frequently have intractable ventricular arrhythmias or complete heart block. Giant cell myocarditis has a poor prognosis but is important to rule out in the setting of an otherwise healthy patient presenting in fulminant heart failure or with intractable arrhythmias because immunosuppressive therapy can help improve survival. 