Infective endocarditis is an infection inside the heart which can affect the valves that control the passage of blood from one heart chamber to the next. Most often the condition is caused by bacteria, and when it develops gradually it is known as subacute bacterial endocarditis, or endocarditis lenta. As damage to heart valves can lead to heart failure, the disorder is serious. For this reason, people who are more at risk of developing it are given preventive treatment, known as prophylaxis. Subacute bacterial endocarditis prophylaxis may be offered to people who have existing heart problems, those whose immune systems are weak, and those who inject illegal drugs.
Bacterial endocarditis arises when bacteria enter the blood, perhaps traveling from a site of infection or a cut or being introduced on a contaminated needle. Although the immune system normally kills most bacteria in the blood, if some manage to survive they may attach themselves to the lining of the heart, particularly the valves. This is more likely to occur where there are structural abnormalities, such as deformed or artificial valves, heart defects which have been present from birth, or areas of previous infection or surgery. Subacute endocarditis may then develop, causing symptoms of fatigue, aching, loss of appetite, and fever. Eventually, a heart murmur may arise when damage to heart valves causes abnormal blood flow through the heart, leading to a distinctive sound when heard through a stethoscope.
Subacute bacterial endocarditis prophylaxis aims to prevent endocarditis from developing by administering antibiotic drugs in situations where a person is thought to be at risk of bacteria entering the blood. Treatment decisions are made according to the individual's risk of endocarditis, the risk associated with a procedure, and the pros and cons of giving the medication. Prophylaxis is only offered to people considered to be more at risk than the general population. Occasionally, even when subacute bacterial endocarditis prophylaxis is carried out, endocarditis may still develop.
Dental procedures are known to cause significant amounts of bacteria to enter the bloodstream. The amount of risk associated with a dental procedure is increased if an individual's mouth is already infected or inflamed, so oral hygiene is an important part of endocarditis prevention. In the case of dental work, subacute bacterial endocarditis prophylaxis may consist of a single antibiotic dose given in advance.
Procedures carried out on the digestive tract, such as intestinal surgery, may also require subacute bacterial endocarditis prophylaxis, as may operations involving the genital and urinary systems, such as prostate surgery. Respiratory system procedures, such as removal of the tonsils, can also require preventive endocarditis treatment. In many cases, a dose of antibiotics is given before an operation is carried out, but some gastrointestinal system or genitourinary system procedures may require more than one dose, or an infusion of antibiotics given over a number of hours.