Inflammation of the lining of the heart, particularly affecting the heart valves, caused by an infection
The internal lining of the heart, the endocardium, may become infected if microorganisms enter the bloodstream and reach the heart. Infection causes the lining, especially over the heart valves, to become inflamed, and bacteria and blood clots can collect over the inflamed areas. The valves are particularly prone to infection if they are already damaged or if they are replacement valves (see Heart valve replacement).
In most cases, infective endocarditis is a chronic (long-term) disorder that develops over weeks or months and causes only vague symptoms, such as a fever and aching joints. Rarely, endocarditis is an acute disorder that may rapidly damage one or more of the heart valves. Within days acute endocarditis may cause acute heart failure, which may be life-threatening.
The most common causes of infective endocarditis are bacteria and, less often, fungi. Normally harmless microorganisms may enter the blood during dental procedures, especially tooth extraction, and operations on the digestive or urinary tracts. The condition can also occur after a medical procedure, such as the insertion of a catheter into the bladder or from long-term treatment using an indwelling intravenous catheter, such as a skin-tunnelled catheter. Rarely, infective endocarditis develops after cardiac surgery, especially if artificial materials, such as replacement heart valves, are inserted into the heart. A person with a suppressed immune system is particularly susceptible to infective endocarditis because his or her body is less able to fight the infection. For example, anyone with HIV infection or AIDS or who is undergoing treatment with anticancer drugs is at increased risk of developing the disorder. People who abuse intravenous drugs are also susceptible because microorganisms can be injected into the bloodstream and travel to the heart. There is an even greater risk of infection if needles are shared. Body piercing and tattooing also carry an increased risk of infection.
The symptoms of chronic endocarditis are often generalized and unrelated to heart damage. They may include:
Fever and night sweats.
Infected material from the valve may break off and block a vessel elsewhere in the body. For example, small clots may lodge in veins under the fingernails or skin, causing tiny splinter-like haemorrhages. If a clot blocks an artery that supplies blood to the brain, it may result in a stroke.
The symptoms of acute endocarditis develop suddenly and may include:
Palpitations (awareness of an irregular or abnormally rapid heartbeat).
These symptoms can rapidly worsen. If acute heart failure develops, there may be other symptoms, such as severe shortness of breath and wheezing.
Chronic infective endocarditis is difficult to diagnose because the symptoms are often unrelated to heart damage. Your doctor may suspect the disorder if he or she hears a new heart murmur or a change in an existing heart murmur. The diagnosis may be confirmed by echocardiography to image the interior of the heart and detect infected material on the surface of the valves. Blood tests may be done to identify the organism responsible for the infection.
If you have infective endocarditis, you will usually need treatment with intravenous antibiotics for about 6 weeks. You will have regular blood tests to confirm that the infection is clearing up. This treatment is successful in up to 4 in 5 cases. If a valve is badly damaged or if the infection cannot be controlled with drugs, heart valve replacement may be necessary.
If you have a valve disorder or already have a replacement valve, you are at increased risk of developing endocarditis and should be aware of the symptoms. Contact your doctor immediately if any become apparent. Once you have had one episode of the disorder, you have an increased risk of developing it again. For this reason, you may be advised to take a single dose of an antibiotic before dental treatment and operations on the digestive or urinary tracts.
From the 2010 revision of the Complete Home Medical Guide © Dorling Kindersley Limited.