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Endocarditis occurs when germs enter your bloodstream, travel to your heart, and attach to abnormal heart valves or damaged heart tissue. Bacteria cause most cases, but fungi or other microorganisms also may be responsible.

Sometimes the culprit is one of many common bacteria that live in your mouth, throat or other parts of your body. The offending organism may enter your bloodstream through:

  • Everyday oral activities. Activities such as brushing your teeth or chewing food can allow bacteria to enter your bloodstream — especially if your teeth and gums are in poor condition.
  • An infection or other medical condition. Bacteria may spread from an infected area, such as a skin sore. Gum disease, a sexually transmitted disease or an intestinal disorder — such as inflammatory bowel disease — also may give bacteria the opportunity to enter your bloodstream.
  • Catheters or needles. Bacteria can enter your body through a catheter — a thin tube that doctors sometimes use to inject or remove fluid from the body. The bacteria that can cause endocarditis can also enter your bloodstream through the needles used for tattooing or body piercing. Contaminated needles and syringes are a concern for people who use intravenous (IV) drugs.
  • Certain dental procedures. Some dental procedures that can cut your gums may allow bacteria to enter your bloodstream.

Typically, your immune system destroys bacteria that make it into your bloodstream. Even if bacteria reach your heart, they may pass through without causing an infection.

Most people who develop endocarditis have a diseased or damaged heart valve — an ideal spot for bacteria to settle. This damaged tissue in the endocardium provides bacteria with the roughened surface they need to attach and multiply.

Aug. 11, 2011