What Causes Endocarditis?

Infective endocarditis (IE) occurs when bacteria, fungi, or other germs invade your bloodstream and attach to abnormal areas of your heart. Certain factors increase the risk of germs attaching to a heart valve or chamber and causing an infection.

A common underlying factor in IE is a structural heart defect, especially faulty heart valves. Usually your immune system will kill germs in your bloodstream. However, if your heart has a rough lining or abnormal valves, the invading germs can attach and multiply in the heart.

Other factors, such as those that allow germs to build up in your bloodstream, also can play a role in causing IE. Common activities, such as brushing your teeth or having certain dental procedures, can allow bacteria to enter your bloodstream. This is even more likely to happen if your teeth and gums are in poor condition.

Having a catheter or other medical devices inserted through your skin, especially for long periods, also can allow bacteria to enter your bloodstream. People who use intravenous (IV) drugs also are at risk for infections due to germs on needles and syringes.

Bacteria also may spread to the blood and heart from infections in other parts of the body, such as the gut, skin, or genitals.

Endocarditis Complications

As the bacteria or other germs multiply in your heart, they form clumps with other cells and matter found in the blood. These clumps are called vegetations (vej-eh-TA-shuns).

As IE worsens, pieces of the vegetations can break off and travel to almost any other organ or tissue in the body. There, the pieces can block blood flow or cause a new infection. As a result, IE can cause a wide range of complications.

Heart Complications

Heart problems are the most common complication of IE. They occur in one-third to one-half of all people who have the infection. These problems may include a new heart murmur, heart failure, heart valve damage, heart block, or, rarely, a heart attack.

Central Nervous System Complications

These complications occur in as many as 20 to 40 percent of people who have IE. Central nervous system complications most often occur when bits of the vegetation, called emboli (EM-bo-li), break away and lodge in the brain.

There, they can cause local infections (called brain abscesses) or a more widespread brain infection (called meningitis).

Emboli also can cause a stroke or seizures. This happens if they block blood vessels or affect the brain's electrical signals. These complications can cause long-lasting damage to the brain and may even be fatal.

Complications in Other Organs

IE also can affect other organs in the body, such as the lungs, kidneys, and spleen.

Lungs. The lungs are especially at risk when IE affects the right side of the heart. This is called right-sided infective endocarditis.

A vegetation or blood clot going to the lungs can cause a pulmonary embolism and lung damage. Other lung complications include pneumonia and a buildup of fluid or pus around the lungs.

Kidneys. IE can cause kidney abscesses and kidney damage. IE also can cause inflammation of the internal filtering structures of the kidneys.

Signs and symptoms of kidney complications include back or side pain, blood in the urine, or a change in the color or amount of urine. In a small number of people, IE can cause kidney failure.

Spleen. The spleen is an organ located in the left upper part of the abdomen near the stomach. In as many as 25 to 60 percent of people who have IE, the spleen enlarges (especially in people who have long-term IE).

Sometimes, emboli also can damage the spleen. Signs and symptoms of spleen problems include pain or discomfort in the upper left abdomen and/or left shoulder, a feeling of fullness or the inability to eat large meals, and hiccups.