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Infectious Endocarditis

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Updated November 13, 2011

Written or reviewed by a board-certified physician. See About.com's Medical Review Board.

Infectious endocarditis (IE) - which sometimes is also called subacute bacterial endocarditis (SBE), or just "endocarditis" - is an infection of the endocardial surface (the interior lining) of the heart. IE is always a serious medical problem, since the infection can destroy your heart valves or heart muscle.

What Causes IE?

Bacteria live normally on your skin, your mouth and your gastrointestinal tract, without causing any serious problems. Even when these bacteria enter the bloodstream (such as during a medical or dental procedure), in most cases the body's defense mechanisms clear the bacteria quickly and efficiently. However, in people who are at increased risk for IE, the bacteria can get trapped within turbulent blood flow inside the heart, and subsequently "stick" to the endocardial lining, where they can cause an infection.

Who Is At Risk?

IE is a potential risk if you have any type of heart valve disease, hypertrophic cardiomyopathy, or a pacemaker or implantable defibrillator. The highest risk, however, is seen in people who have had heart valve replacement surgery, a prior episode of IE, incompletely repaired congenital heart disease, or, most especially, people who are intravenous drug users.

What Are The Effects of IE?

IE can cause abscesses to form in the heart tissue, which can result in the destruction of heart valves and cardiac muscle, leading to leaky heart valves ("regurgitation") and heart failure. Untreated or inadequately treated IE is often fatal.

The bacteria that cause the IE, along with immune cells and platelets that the body sends to fight the bacteria, can form "vegetations" - clumps of tissue that cling to the endocardial surface of the heart. These vegetations can continually "seed" the bloodstream with bacteria, so that new areas of infection can appear elsewhere within the body. Further, the vegetations themselves can break off into the bloodstream (a condition which is referred to as embolization), and block blood vessels. So, for instance, an embolized vegetation can cause a stroke.

What Are The Symptoms of IE?

Acute (recent onset) IE often feels like the flu, with fever, shaking chills, sweats, aching muscles, and weakness. Chronic IE is a more subtle form of the illness, and often manifests with chronic, non-specific symptoms - such as vague aches and pains, chills, weight loss, joint pain or swelling, and weakness.

People with chronic IE can also have some less common but more specific signs of the condition. These include linear red streaks under the nails (splinter hemorrhages), red spots on the palms and soles (Janeway lesions) and, painful red bumps on the pads of the fingers and toes (Osler's nodes). If the IE progresses enough to produce significant heart damage, patients may experience shortness of breath, swelling of the ankles, and other symptoms of heart failure.

Diagnosing IE

The key to making the diagnosis of IE is to suspect it. Any symptoms like those just listed, which occur in a person who is at risk for IE, especially if a there has been a recent medical or dental procedure, should make the doctor think of the possibility of IE.

The diagnosis is made by the medical history, by the physical examination (especially a change in the heart sounds, or a new heart murmur), by drawing "blood cultures" (attempting to grow bacteria from blood samples), and by echocardiogram (looking for changes in the structure of the heart valves, or for vegetations).

Treating IE

IE is treated with antibiotics, usually administered intravenously, and usually for several weeks. If heart valve damage has occurred, or if threatening vegetations are seen with echocardiography, heart surgery may be required.

The type of antibiotics that are used, and the length of time you will have to be hospitalized, depends on which kind of bacteria is causing the infection, and on the extent of heart muscle or heart valve damage.

If you have either a pacemaker or implantable defibrillator, developing IE means the entire implanted system (both the device and the leads) will have to be completely removed in order to cure the infection. A new device and new leads can be re-inserted once your bloodstream is free of bacteria.

Preventing IE

Endocarditis prophylaxis - taking antibiotics before dental or medical procedures to try to prevent endocarditis - can be useful in people who are at the very highest risk of developing IE. Here is a discussion of endocarditis prophylaxis - who needs it, and when they need it.

Sources:

Murdoch, DR, Corey, GR, Hoen, B, et al. Clinical presentation, etiology, and outcome of infective endocarditis in the 21st century: the International Collaboration on Endocarditis-Prospective Cohort Study. Arch Intern Med 2009; 169:463.

Bayer, AS. Infective endocarditis. Clin Infect Dis 1993; 17:313.

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