Myocarditis
A focal or diffuse inflammation of the myocardium, myocarditis typically is uncomplicated and self-limiting. It may be acute or chronic and can occur at any age. In many patients, myocarditis fails to produce specific cardiovascular symptoms or electrocardiogram (ECG) abnormalities. Recovery is usually spontaneous and without residual defects.
Occasionally, myocarditis may become serious and induce myofibril degeneration, right- and left-sided heart failure with cardiomegaly, and arrhythmias.
Causes
Myocarditis may result from any of the following:
viruses—the most common causes in the United States and western Europe—including coxsackievirus A and B; possibly, those that cause poliomyelitis, influenza, rubeola, and rubella; human immunodeficiency virus; adenoviruses; and echoviruses
bacteria, including those that cause diphtheria, tuberculosis, typhoid fever, tetanus, and Lyme disease, and staphylococcal, pneumococcal, and gonococcal bacteria
hypersensitive immune reactions, such as acute rheumatic fever and postcardiotomy syndrome
radiation therapy, especially large doses to the chest during treatment of lung or breast cancer
chemical poisoning such as in chronic alcoholism
parasitic infections, especially toxoplasmosis and South American trypanosomiasis (Chagas’ disease) in infants and immunosuppressed adults
helminthic infections such as trichinosis.
Complications
Occasionally, myocarditis is complicated by left-sided heart failure. Rarely, it leads to cardiomyopathy. Sometimes myocarditis recurs or produces chronic valvulitis (when it results from rheumatic fever), cardiomyopathy, arrhythmias, or thromboembolism.
Assessment
The patient history commonly reveals a recent upper respiratory tract infection with fever, viral pharyngitis, or tonsillitis. The patient may complain of nonspecific symptoms, such as fatigue, dyspnea, palpitations, persistent tachycardia, and persistent fever, all of which reflect the accompanying systemic infection. Occasionally, the patient may complain of a mild, continuous pressure or soreness in the chest. This pain, however, is unlike the recurring, stress-related pain of angina pectoris.
Auscultation commonly reveals S3 and S4 gallops, a muffled S1
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