Endocarditis, Infectious

Infectious endocarditis (in-FEK-shus en-do-kar-DYE-tis) is an inflammation of the valves and internal lining of the chambers of the heart, known as the endocardium (en-doh-KAR-dee-um), Endocarditis is initiated by an infection.

What Is Endocarditis?

To understand endocarditis, it is helpful to begin by reviewing the structure of the human heart. The heart has four chambers and four valves that regulate the flow of blood through the heart. Each valve is made up of two or three smaller parts, known as leaflets that swing open and shut. As the heart beats, it pumps blood through the chambers and outward from the heart to the lungs and the rest of the body. The valves open to allow blood to pass through and out of the heart and then close to keep the blood from flowing backward.

In a normal heart, the swift, smooth movement of blood sweeps foreign material such as bacteria away from the heart. However, some people have defects in their heart valves, the endocardium, or other parts of the heart that disrupt the flow of blood. This disruption can allow bacteria or other germs that reach the heart through the bloodstream to lodge there and multiply, which results in an infection that inflames the heart valves, muscles, and endocardium, producing endocarditis. The inflammation (in-flab-MAY-shun), which is the body's response to injury or infection, can be significant, in which case it may damage or even destroy the heart valves.

Infectious endocarditis can start suddenly or develop gradually over weeks or months. Viruses, fungi, or other microscopic organisms can all cause infectious endocarditis, but the disease usually arises from a bacterial infection. A common bacterium abundant in the oral cavity, Streptococcus viridans (strep-tuh-KAH-kus VEER-ih-danz), is responsible for as many as half of all cases of bacterial endocarditis. Other bacterial culprits include bacteria from the Staphylococcus, Streptococcus, and Enterococcus genuses and, less commonly, other types.

In most cases of infectious endocarditis, bacteria that live normally and harmlessly on the body, such as in the mouth, on the skin, in the intestines * , or in the urinary tract * (POOR-ih-nair-e TRAKT), enter the blood (a condition known as bacteremia [bak-tuh-REE-me-uh]). The bacteria can enter tissues through a cut or a tear that has resulted from a dental or medical procedure, or they may enter the blood because of a site of infection somewhere else in the body.

In addition, intravenous drug users are at high risk for infectious endocarditis because Staphylococcus bacteria in the skin have many opportunities to enter the bloodstream through broken skin. When in the bloodstream, the bacteria travel to the heart and may stick to the endocardium or heart valves. As they grow and multiply, the bacteria may become entangled in clumps of platelets * , bacteria, red and white blood cells, and fibrin, which is a protein that helps with blood clotting * .

How Common Is Infectious Endocarditis?

Infectious endocarditis is not common among people with normal hearts, but people with a heart abnormality are more susceptible to it. Because bacteria can attach easily to a malformed or damaged part of the heart, people with an artificial or damaged heart valve or a heart defect are more likely to get endocarditis. Anyone who has had infectious endocarditis or who has an indwelling catheter * has a greater chance of becoming infected. Although many people with heart defects are born with them, other people acquire the defects during their lifetime, such as from intravenous * drug use or rheumatic fever * , which puts them at increased risk for endocarditis as well. Between 2000 and 2011 in the United States, the incidence of infective endocarditis increased from 11 per 100,000 people to 15 per 100,000 people.

Infectious endocarditis is not contagious, so there is no reason to avoid contact with individuals who have it.

How Do People Know They Have Infectious Endocarditis?

Flulike symptoms, such as fever, chills, and weakness, are the most common symptoms of infectious endocarditis. Some people experience weight loss, weakness, headache, tiredness, shortness of breath, joint and muscle pain, and excessive sweating at night (night sweats). A heart murmur * usually develops during the course of the illness. Individuals may look pale, have red spots on their skin, and see blood in their urine. An enlarged spleen * ; small hemorrhages * in the nail beds and in the whites of the eyes; and swelling of the feet, legs, and abdomen can also occur with infectious endocarditis.

How Do Doctors Diagnose and Treat Infectious Endocarditis?


Doctors may suspect infectious endocarditis if someone with a known heart abnormality develops an unexplained long-lasting fever, an abnormal heart sound (a murmur), or symptoms of heart failure such as shortness of breath or swelling of the legs.


Doctors treat infectious endocarditis with antibiotics. The medication is given intravenously in the hospital at first, but sometimes patients complete the treatment at home. Several weeks of antibiotic treatment may be necessary to eliminate the infection. In more serious cases, patients may need oxygen and other medications to support heart function while hospitalized, and some people require surgery to repair damage sustained by the heart as a result of the inflammation. Left untreated, infectious endocarditis is often fatal.


Infectious endocarditis can cause complications. In some people with the disease, small pieces of material in the heart may break off and travel through the bloodstream to other organs. If one of these pieces travels to the brain and blocks a blood vessel there, for example, the affected person may have a stroke * . If the pieces lodge in other organs, they may cause serious infections there. Infectious endocarditis that is allowed to progress can also result in an irregular heartbeat, congestive heart failure, jaundice * , kidney failure, and heart failure.

Can Infectious Endocarditis Be Prevented?

Doctors prescribe antibiotics to people as a protective measure before their patients undergo dental or medical procedures that could introduce bacteria into the bloodstream. For example, simple dental work, removal of the tonsils, or medical procedures in which parts of the upper respiratory system (such as the mouth and throat), urinary tract (specifically the urethra * ), or lower gastrointestinal * tract are involved can all provide an avenue for bacteria to enter the bloodstream and travel to the heart.

See also Addiction • Heart Disease: Overview • Rheumatic Fever • Staphylococcal Infections • Streptococcal Infections



MedlinePlus. “Endocarditis.” U.S. National Library of Medicine. https://www.nlm.nih.gov/medlineplus/endocarditis.html (accessed October 13, 2015).

Sexton, Daniel, J. “Epidemiology, Risk Factors, and Microbiology of Infective Endocarditis.” 2015. http://www.uptodate.com/contents/epidemiology-risk-factors-and-microbiology-of-infectiveendocarditis?source=search_result&search=epidemiology+risk+factors+and+microbiologyof+infective+endocarditis&selectedTitle=1~150 (accessed June 3, 2016).


American Heart Association. 7272 Greenville Ave., Dallas, TX 752314596. Toll-free: 800-AHA-USA1. Website: http://heart.org/HEARTORG/ (accessed October 13, 2015).

National Heart, Lung, and Blood Institute. PO Box 30105, Bethesda, MD 20824-0105. Telephone: 301-592-8573. Website: http://www.nhlbi.nih.gov (accessed October 13, 2015).

* intestines are the smooth muscle tubes through which food passes during digestion after it exits the stomach.

* urinary tract (YOOR-ih-nair-e TRAKT) is the system of organs and channels that makes urine and removes it from the body. It consists of the urethra, bladder, ureters, and kidneys.

* platelets (PLATE-lets) are tiny disk-shaped particles within the blood that play an important role in clotting.

* clotting is the process by which the body forms a thickened mass of blood cells and protein to stop bleeding.

* catheter (KAH-thuh-ter) is a small plastic tube placed through a body opening into an organ (such as the bladder) or through the skin directly into a blood vessel. It is used to give fluids to or drain fluids from a person.

* intravenous (in-tra-VEE-nus), or IV, means within or through a vein. For example, medications, fluid, or other substances can be given through a needle or soft tube that penetrates the skin's surface and is inserted directly into a vein.

* rheumatic fever (roo-MAH-tik) is a disease associated with fever, joint pain, and inflammation of many body tissues, including parts of the heart. It occurs after infection with certain types of streptococcal bacteria.

* heart murmur is an abnormal sound from the heart, heard with a stethoscope, that is usually related to abnormal flow of blood through the heart. Some murmurs indicate a problem with a heart valve or other part of the heart's structures, but many heart murmurs are benign (do not indicate any problem).

* spleen is an organ in the upper left part of the abdomen that stores and filters blood. As part of the immune system, the spleen also plays a role in fighting infection.

* hemorrhage (HEH-muh-rij) is uncontrolled or abnormal bleeding.

* stroke is a brain-damaging event usually caused by interference with blood flow to and within the brain. A stroke may occur when a blood vessel supplying a region of the brain becomes clogged or bursts, depriving brain tissue of oxygen. As a result, nerve cells in the affected area of the brain, and the specific body parts they control, do not function properly.

* jaundice (JON-dis) is a yellowing of the skin, and sometimes the whites of the eyes, caused by a buildup in the body of bilirubin, a chemical produced in and released by the liver. An increase in bilirubin may indicate disease of the liver or certain blood disorders.

* urethra (yoo-REE-thra) is the tube through which urine passes from the bladder to the outside of the body.

* gastrointestinal (gas-tro-in-TEStih-nuhl) means pertaining to the organs of the digestive system, the system that processes foods and liquids. It includes the mouth, esophagus, stomach, intestines, colon, and rectum, and other organs involved in digestion, including the liver and pancreas.

Disclaimer:   This information is not a tool for self-diagnosis or a substitute for professional care.

(MLA 8th Edition)