MYOCARDIAL DISEASE - MYOCARDITIS



Acute myocardial inflammation is termed my­ocarditis and may be associated with fever, dysp­nea, edema, fatigue, palpitations, and pleuropericardial pain. Myocarditis is frequently not clinically apparent and is suspected only on the basis of ST and T wave changes or a transient con­duction defect on electrocardiography in a patient with a systemic illness. Physical examination may reveal signs of pericarditis or biventricular car­diac failure. Intraventricular or atrioventricular conduction disturbances or arrhythmias may occur.

Therapy is usually supportive. Congestive heart failure responds to routine management with dig­italis, diuresis, and afterload reduction. Signifi­cant arrhythmias should be treated with antiar­rhythmic’agents. Steroids may be of benefit in acute rheumatic carditis but should be avoided in suspected infectious myocarditis. Immunosup­pressive therapy may be helpful in selected pa­tients.
Most patients recover completely. An unknown percentage of patients, probably small, develop a chronic process leading to a dilated cardiomy­opathy after a varying latency period.

Infectious agents cause myocarditis by three basic mechanisms: (1) invasion of the myocar­dium, (2) production of a myocardial toxin, for example, diphtheria, and (3) autoimmunity, as in acute rheumatic fever. The infectious agents are multiple, most commonly thought to be viral, es­pecially Coxsackie group B. Primary bacterial my­ocarditis is a rare but grave complication of bac­terial endocarditis, most commonly caused by streptococci or staphylococci. Mycoplasma pneu­moniae infections, toxoplasmosis, trichinosis, and rickettsial diseases such as Rocky Mountain spotted fever are associated with myocarditis. Protozoal myocarditis from trypanosomiasis (Chagas’ disease) is common in Central and South America where it is a frequent cause of chronic congestive cardiomyopathy, heart block, and ven­tricular arrhythmias. Hypersensitivity reactions to various agents and radiation therapy can result in inflammation of the myocardium.