is an
Inflammation of the inner layer of the
Heart , the
Endocardium . The most common structures involved are the
Heart Valve s.
Endocarditis can be classified by etiology as either ''infective'' or ''non-infective'', depending on whether a
Microorganism is the source of the problem.
As the valves of the heart do not actually receive any
Blood supply of their own, which may be surprising given their location, defense mechanisms (such as
White Blood Cell s) cannot enter. So if an organism (such as
Bacteria ) establish hold on the valves, the body cannot get rid of them.
Normally, blood flows smoothly through these valves. If they have been damaged (for instance in
Rheumatic Fever ) bacteria have a chance to take hold.
Traditionally, infective endocarditis has been clinically divided into ''acute'' and ''subacute'' (between acute and chronic) endocarditis. This classifies both the tempo of progression and severity of disease. Thus subacute bacterial endocarditis (SBE) is often due to streptococci of low virulence and mild to moderate illness which progresses slowly over weeks and months, while acute bacterial endocarditis (ABE) is a fulminant illness over days to weeks, and is more likely due to ''
Staphylococcus Aureus '' which has much greater virulence, or disease-producing capacity.
This terminology is now discouraged. The terms ''short incubation'' (meaning less than about six weeks), and ''long incubation'' (greater than about six weeks) are preferred despite the lack of advantage in meaning.
Infective endocarditis may also be classified as ''culture-positive'' or ''culture-negative''. Culture-negative endocarditis is due to micro-organisms that require a longer period of time to be identified in the laboratory. Such organisms are said to be ''fastidious'' because they have demanding growth requirements. Some pathogens responsible for culture-negative endocarditis include ''Aspergillus species'', ''Brucella species'', ''Coxiella burnettii'', ''Chlamydia species'', and HACEK bacteria.
Finally, the distinction between ''native-valve endocarditis'' and ''prosthetic-valve endocarditis'' is clinically important.
As previously mentioned, altered blood flow around the valves is a risk factor in obtaining endocarditis. The valves may be damaged congenitally, from
Surgery , by
Auto-immune mechanisms, or simply as a consequence of old age. The damaged part of a heart valve becomes covered with a blood clot, a condition known as non-bacterial thrombotic endocarditis (NBTE).
In a healthy individual, a
Bacteraemia (where bacteria get into the blood stream through a minor cut or wound) would normally be cleared quickly with no adverse consequences. If a heart valve is damaged and covered with a piece of a blood clot, the valve provides a place for the bacteria to attach themselves and an infection can be established.
The bacteraemia is often caused by minor
Dental procedures, such as a
Tooth removal. It is important that a
Dentist is told of any heart problems before commencing.
Another group of causes result from a high number of bacteria getting into the bloodstream.
Colorectal Cancer , serious
Urinary Tract Infection s and
IV Drug use, can all introduce large numbers of bacteria. With a large number of bacteria, even a normal heart valve may be infected. A more virulent organism (such as ''
Staphylococcus Aureus '') is usually responsible for infecting a normal valve.
Intravenous drug users tend to get their right heart valves infected because the
Vein s that are injected enter the right side of the heart. The injured valve is most commonly affected when there is a pre-existing disease. (In rheumatic heart disease this is the aortic and the mitral valves, on the left side of the heart.)
- Fever (often spiking)
- Continuous presence of micro-organisms in the bloodstream determined by serial collection of blood cultures
- Vegetations on valves on Echocardiography
- Septic emboli, causing circulatory problems ( Stroke , Gangrene of fingers)
- Chronic Renal Failure
- Osler's Node s (painful subcutaneous lesions in the distal fingers)
- Janeway Lesion s (painless hemorrhagic cutaneous lesions on the palms and soles)
- Roth Spot s on the Retina
- Conjunctival petechiae
- A new or changing heart murmur, particularly murmurs suggestive of valvular incompetence
Many types of organism can cause infective endocarditis. These are generally isolated by
Blood Culture , where the patient's blood is removed, and any growth is noted and identified.
Alpha-haemolytic
Streptococci , that are present in the mouth will often be the organism isolated if a dental procedure caused the bacteraemia.
If the bacteraemia was introduced through the skin, such as contamination in surgery, during catheterisation, or in an IV drug user, ''Staphylococcus aureus'' is common.
A third important cause of endocarditis is ''
Enterococci ''. These bacteria enter the bloodstream as a consequence of abnormalities in the gastrointestinal or urinary tracts. ''
Enterococci '' are increasingly recognized as causes of nosocomial or hospital-acquired endocarditis. This contrasts with alpha-haemolytic streptococci and ''
Staphylococcus Aureus '' which are causes of community-acquired endocarditis.
Some organisms, when isolated, give valuable clues to the cause, as they tend to be specific.
- '' Candida Albicans '', a Yeast , is associated with IV drug users and the Immunocompromised .
- '' Pseudomonas '' species, which are very resilient organisms that thrive in water, may contaminate street drugs that have been contaminated with drinking water.
- '' Streptococcus Bovis '', which is part of the natural flora of the bowel, tends to present when the patient has bowel cancer.
- HACEK Organisms are a group of bacteria that live on the dental gums, and are associated with IV drug users who contaminate their needles with saliva.
High dose
Antibiotic s are administered by the intravenous route to maximize diffusion of antibiotic molecules into vegetation(s) from the blood filling the chambers of the heart. This is necessary because neither the heart valves nor the vegetations adherent to them are supplied by blood vessels. Antibiotics are continued for a long time, typically two to six weeks. Surgical removal of the valve is necessary in patients who fail to clear micro-organisms from their blood in response to antibiotic therapy, or in patients who develop cardiac failure resulting from destruction of a valve by infection. A removed valve is usually replaced with an artificial valve which may either be mechanical (metallic) or obtained from an animal such as a pig; the latter are termed bioprosthetic valves.
Infective endocarditis is associated with a 25% mortality.
Non-infective or marantic endocarditis is
Rare . A form of sterile endocarditis is termed
Libman-Sacks Endocarditis ; this form occurs more often in patients with
Lupus Erythematosus and the
Antiphospholipid Syndrome . Non-infective endocarditis may also occur in patients with cancers, particularly mucinous adenocarcinoma.
