Heart tissue is composed of three layers: the pericardium, (the thin, fibrous membrane surrounding the heart), the myocardium (the thick, muscular layer) and the endocardium (the inner lining of the heart's chambers and valves). The illustration below provides a good view of these components. An infection of the heart can be isolated within a single layer, or affect all layers simultaneously. Naturally, the presence of any cardiac infection should be regarded as a medical emergency and appropriate treatment should be commenced as soon as a diagnosis is confirmed.
Many factors can contribute to the development of a heart infection. The infectious agent may be a bacterium, virus, fungus, or even a parasite. A frequent culprit is rheumatic fever, a disease triggered by a particular type of streptococcus (group A) bacteria. The bacteria itself does not cause rheumatic fever, but the interaction between toxins produced by this bacteria (antigens) and the body's natural defensive substances (antibodies) sometimes combine to produce this "reactive" disease in certain people. There may be a genetic predisposition to the development of rheumatic fever, as less that 3% of streptococcus infections degenrate into this condition. When it does appear, rheumatic fever is often preceeded by a throat infection. Symptoms include a fever, painful and swollen joints accompanied by a variety of skin rashes. An iflammation of the heart is characteristic of this disease, and will manifest as pericarditis, an inflammation of the outer lining of the heart, myocarditis, involving the heart's muscular tissue, or endocarditis, an infection of the inner lining of the heart and valves. Of course, these infections may be triggered by other factors, many of which will be explored at present.
Acute Pericarditis:
In addition to rheumatic fever, the incidence of pericarditis may be attributed to a virus, bacteria, fungus, parasite, an allergic reaction to certain drugs or a penetrating injury to the heart. This condition can also develop in conjunction with a severe heart attack or may arise from an immunologic reaction following heart surgery.
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