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inflammation of the heart muscle (myocardium). Myocarditis may be caused by infectious diseases, including viral ones, and by an allergic reaction, which is the main pathogenic factor in drug-induced and serum myocarditis. The role of autoimmunities and allergies is manifested in postinfluenzal myocarditis, in which the acute infectious disease (influenza) passes but the myocarditis caused by it persists for many months. Contemporary medicine generally accepts the theory that most forms of myocarditis are caused by infections and allergies. Myocarditis is a common symptom of collagen diseases, such as rheumatism, systemic lupus erythematosus, and scleroderma. In South America, Africa, and Polynesia myocarditis may be caused by parasitic diseases. In many cases the cause of myocarditis is unidentified.
Myocarditis may be diffuse or focal. Depending on the course of the disease, cases are categorized as acute, subacute, and chronic (recurrent). Cases may be mild, extremely severe, or fatal. In acute myocarditis patients commonly complain that they feel weak, tire easily, and are short of breath. They suffer from rapid heartbeat (tachycardia), arrhythmia, and pain in the heart. Pallor is also a common symptom. Arterial pressure is low, and venous pressure high, owing to the decreased force of heart contractions. The cervical veins in the neck swell, and the heart becomes enlarged. Various irregularities in cardiac contractions and conduction, to the point of complete atrioventricular heart block, are common and are accompanied by specific electrocardiographic changes. Often there are no clear-cut symptoms of myocarditis, and death occurs unexpectedly from severe injury to the myocardium. Of particular importance in diagnosing such cases are electrocardiography and laboratory tests, including blood count, analysis of protein and protein fractions, determination of enzymic activity, and immunologic studies.
The characteristics of myocarditis vary, depending on the origin of the disease. The most common form, rheumatic myocarditis, is usually accompanied by endocarditis, which results in heart defects. Pain in the heart and irregularities in cardiac rhythm and conduction are the most common symptoms of active rheumatic endocarditis. The causes and developmental mechanisms of idiopathic myocarditis, the most severe form of the disease, are still obscure. Nonetheless, a number of varieties have been distinguished. In one of them, symptoms of cardiovascular insufficiency prevail, accompanied by arrhythmia and the development of pulmonary and renal infarctions and of circulatory disorders in the cerebrum. Another variety is associated with pain in the heart and with EKG changes, and still another, with the development of relative valvular inefficiency due to cardiomegaly. One type of idiopathic myocarditis is manifested by a mixture of symptoms associated with other varieties of the disease.
Diphtherial myocarditis, which occurs in approximately 25–30 percent of all diphtheria patients, usually develops in the second week of the disease. Its most characteristic symptom is disturbance of conduction, to the point of complete atrioventricular heart block. Prompt therapy usually results in recovery, and cardiac disorders persist in only a few patients.
Treatment includes complete rest and the prescription of vitamins (C, B-complex), steroid hormones, and anti-infectious and antiarrhythmic medicines. Salicylates are prescribed in cases of rheumatic endocarditis, and appropriate drugs are prescribed for cardiovascular insufficiency.
REFERENCEKedrov, A. A. Bolezni myshtsy serdtsa. Leningrad, 1963.
N. R. PALEEV