Bacterial endocarditis
| Infective endocarditis | |
|---|---|
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| A mitral valve vegetation caused by bacterial endocarditis. | |
| Classification and external resources | |
| Specialty | Cardiology, infectious disease |
| ICD-10 | I33 |
| ICD-9-CM | 421.0-421.1 |
| MedlinePlus | 000681 |
Infective endocarditis is a form of endocarditis. It is an inflammation of the inner tissues of the heart, the endocardium, usually of the valves. It is caused by infectious agents, or pathogens, which are largely bacterial but a few other organisms can also be responsible. Before the age of modern antibiotics it was almost universally fatal.
The valves of the heart do not receive any dedicated blood supply. As a result, defensive immune system mechanisms (such as white blood cells) cannot directly reach the valves via the bloodstream. If an organism (such as bacteria) attaches to a valve surface and forms a vegetation, the host's immune response is blunted. The lack of blood supply to the valves also has implications for treatment, since drugs also have difficulty reaching the infected area.
Normally, blood flows smoothly through these valves. If they have been damaged — from rheumatic fever, for example — the risk of bacterial attachment is increased.
Historically, infective endocarditis has been clinically divided into acute and subacute presentations (because untreated patients tended to live longer with the subacute as opposed to the acute form). This classifies both the rate of progression and severity of disease.
This classification is now discouraged, because the ascribed associations (in terms of organism and prognosis) were not strong enough to be relied upon clinically. The terms short incubation (meaning less than about six weeks), and long incubation (greater than about six weeks) are preferred.
Infective endocarditis may also be classified as culture-positive or culture-negative. By far the most common cause of a "culture-negative" endocarditis is prior administration of antibiotics.
Sometimes microorganisms can take a longer period of time to grow in the culture media, such organisms are said to be fastidious because they have demanding growth requirements. Some examples include pathogens like Aspergillus species, Brucella species, Coxiella burnetii, Chlamydia species, and HACEK bacteria. Due to delay in growth and identification in these cases, patients may be erroneously classified as "culture-negative" endocarditis.
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