Endocarditis Health Article

Definition

Endocarditis is an infection of the endocardium, the inner lining of the heart muscle and its four valves (tricuspid, pulmonary, mitral, and aortic). Abnormal or damaged endocardium is more likely to become infected when bacteria enter the bloodstream. When this happens, during surgical or dental procedures, for example, a condition called bacteremia results. The circulating bacteria can then enter the heart, where damaged tissue or other abnormalities allow them to multiply and cause an infection. Endocarditis is a life-threatening disease that interferes with the heart's ability to pump blood. Untreated, it is always fatal.

Description

Endocarditis most commonly occurs in people whose hearts have damaged valves. This may be the result of acquired valvular disease from rheumatic fever or other diseases. Patients with mitral valve prolapse, in which a poorly functioning mitral valve regurgitates blood back into the heart, allowing bacteria to multiply, are also at risk for endocarditis. Prosthetic (artificial) heart valves are more likely to become infected as well.

Bacteremia that causes endocarditis can occur in several ways:

• from a localized infection such as a urinary tract infection, pneumonia, skin infection, or dental infection
• as a result of certain medical conditions, such as severe periodontal disease, colon cancer, or inflammatory bowel disease
• during dental or surgical procedures, such as dental cleaning, tooth extractions, tonsil removal, or endoscopic examinations
• through in-dwelling catheters used for intravenous medications, intravenous feeding, or dialysis
• intravenous drug use using unsterilized, contaminated needles and syringes

The bacteria that cause most endocarditis are gram-positive cocci, such as Staphylococcus or Streptococcus. Staphylococcal endocarditis occurs most often among intravenous drug users and patients with in-dwelling venous catheters. Gram-negative bacterial endocarditis or fungal endocarditis is much less common; patients are usually intravenous drug users or those with prosthetic heart valves.

Endocarditis patients who appear critically ill are usually suffering from acute bacterial endocarditis, while those with subacute bacterial endocarditis have less severe but persistent symptoms such as weight loss, fatigue, and low-grade fever.

If not discovered and treated, endocarditis can permanently damage the heart valves. If a valve is damaged, it may allow blood to flow backward—a condition known as regurgitation. As a result of a poorly functioning

valve, the heart muscle has to work harder to pump blood and may become weakened, leading to congestive heart failure.

Another danger associated with endocarditis is that the overgrowth of bacteria colonizing heart valves may break off and form emboli that can become lodged in arteries. An embolism to an artery supplying the brain can cause a stroke; an embolus lodged in the blood vessels of the lungs may cause pneumonia.

Causes and symptoms

Most cases of infective endocarditis occur in patients between the ages of 15 and 60, with a median age at onset of about 50 years. Men are affected about twice as often as women. Other risk factors for endocarditis are congenital heart problems, heart surgery, past history of endocarditis, and intravenous drug use.

Patients with acute bacterial endocarditis are generally critically ill. Patients with subacute bacterial endocarditis tend to have a low-grade fever, which rarely rises above 102°F (38.9°C), chills, weakness, cough, difficulty breathing, headaches, arthralgias (aching joints), and loss of appetite, although these symptoms vary with individual patients.

Emboli may also cause a variety of symptoms, depending on their location. Emboli throughout the body may cause Osler's nodes, which are small, reddish, painful bumps most commonly found on the inside of fingers and toes. Emboli may also cause petechiae, which are tiny purple or red spots on the skin resulting from hemorrhages under the skin's surface. Tiny hemorrhages resembling splinters may also appear under the fingernails or toenails. If emboli become lodged in the blood vessels of the lungs, they may cause coughing or shortness of breath. Emboli lodged in the brain may cause a stroke, with such symptoms as numbness, weakness, or paralysis on one side of the body or sudden blindness or double vision. Emboli may also damage the kidneys, causing nephritis. Sometimes the capillaries on the surface of the spleen rupture, causing it to become enlarged and tender. Patients with any of these symptoms require immediate medical attention.