(redirected from Subacute bacterial endocarditis (SBE))
Also found in: Dictionary, Thesaurus, Encyclopedia.




The endocardium is the inner lining of the heart muscle, which also covers the heart valves. When the endocardium becomes damaged, bacteria from the blood stream can become lodged on the heart valves or heart lining. The resulting infection is known as endocarditis.


The endocardium lines all four chambers of the heart—two at the top (the right and left atria) and two at the bottom (the right and left ventricles)—through which blood passes as the heart beats. It also covers the four valves (the tricuspid valve, the pulmonary valve, the mitral valve, and the aortic valve), which normally open and close to allow the blood to flow in only one direction through the heart during each contraction.
For the heart to pump blood efficiently, the four chambers must contract and relax, and the four valves must open and close, in a well coordinated fashion. By damaging the valves or the walls of the heart chambers, endocarditis can interfere with the ability of the heart to do its job.
Endocarditis rarely occurs in people with healthy, normal hearts. Rather, it most commonly occurs when there is damage to the endocardium. The endocardium may be affected by a congenital heart defect, such as mitral valve prolapse, in which blood leaks through a poorly functioning mitral valve back into the heart. It may also be damaged by a prior scarring of the heart muscle, such as rheumatic fever, or replacement of a heart valve. Any of these conditions can damage the endocardium and make it more susceptible to infection.
Bacteria can get into the blood stream (a condition known as bacteremia) in a number of different ways: It may spread from a localized infection such as a urinary tract infection, pneumonia, or skin infection or get into the blood stream as a result of certain medical conditions, such as severe periodontal disease, colon cancer, or inflammatory bowel disease. It can enter the blood stream during minor procedures, such as periodontal surgery, tooth extractions, teeth cleaning, tonsil removal, prostate removal, or endoscopic examination. It can also be introduced through in-dwelling catheters, which are used for intravenous medications, intravenous feeding, or dialysis. In people who use intravenous drugs, the bacteria can enter the blood stream through unsterilized, contaminated needles and syringes. (People who are prone to endocarditis generally need to take prescribed antibiotics before certain surgical or dental procedures to help prevent this infection.)
If not discovered and treated, infective endocarditis can permanently damage the heart muscle, especially the valves. For the heart to work properly, all four valves must be functioning well, opening at the right time to let blood flow in the right direction and closing at the right time to keep the blood from flowing in the wrong direction. If the valve is damaged, this 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 heart failure. Heart failure is a chronic condition in which the heart is unable to pump blood well enough to supply blood adequately to the body.
Another danger associated with endocarditis is that the vegetation formed by bacteria colonizing on heart valves may break off, forming emboli. These emboli may travel through the circulation and become lodged in blood vessels. By blocking the flow of blood, emboli can starve various tissues of nutrients and oxygen, damaging them. For instance, an embolus lodged in the blood vessels of the lungs may cause pneumonia-like symptoms. An embolus may also affect the brain, damaging nerve tissue, or the kidneys, causing kidney disease. Emboli may also weaken the tiny blood vessels called capillaries, causing hemorrhages (leaking blood vessels) throughout the body.

Causes and symptoms

Most cases of infective endocarditis occur in people 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 are. Other factors that put people at increased risk for endocarditis are congenital heart problems, heart surgery, previous episodes of endocarditis, and intravenous drug use.
While there is no single specific symptom of endocarditis, a number of symptoms may be present. The most common symptom is a mild fever, which rarely goes above 102°F (38.9°C). Other symptoms include chills, weakness, cough, trouble breathing, headaches, aching joints, and loss of appetite.
Emboli may also cause a variety of symptoms, depending on their location. Emboli throughout the body may cause Osler's nodes, small, reddish, painful bumps most commonly found on the inside of fingers and toes. Emboli may also cause petechiae, 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 symptoms of a mini-stroke, such as numbness, weakness, or paralysis on one side of the body or sudden vision loss or double vision. Emboli may also damage the kidneys, causing blood to appear in the urine. Sometimes the capillaries on the surface of the spleen rupture, causing the spleen to become enlarged and tender to the touch. Anyone experiencing any of these symptoms should seek medical help immediately.


Doctors begin the diagnosis by taking a history, asking the patient about the symptoms mentioned above. During a physical examination, the doctor may also uncover signs such as fever, an enlarged spleen, signs of kidney disease, or hemor-rhaging. Listening to the patient's chest with a stethoscope, the doctor may also hear a heart murmur. A heart murmur may indicate abnormal flow of blood through one of the heart chambers or valves.
Doctors take a sample of the patient's blood to test it for bacteria and other microorganisms that may be causing the infection. They usually also use a test called echocardiography, which uses ultrasound waves to make images of the heart, to check for abnormalities in the structure of the heart wall or valves. One of the tell-tale signs they look for in echocardiography is vegetation, the abnormal growth of tissue around a valve composed of blood platelets, bacteria, and a clotting protein called fibrin. Another tell-tale sign is regurgitation, or the backward flow of blood, through one of the heart valves. A normal echocardiogram does not exclude the possibility of endocarditis, but an abnormal echocardiogram can confirm its presence. If an echocardiogram cannot be done or its results are inconclusive, a modified technique called transesophageal echocardiography is sometimes performed. Transesophageal echocardiography involves passing an ultrasound device into the esophagus to get a clearer image of the heart.


When doctors suspect infective endocarditis, they will admit the patient to a hospital and begin treating the infection before they even have the results of the blood culture. Their choice of antibiotics depends on what the most likely infecting microorganism is. Once the results of the blood culture become available, the doctor can adjust the medications, using specific antibiotics known to be effective against the specific microorganism involved.
Unfortunately, in recent years, the treatment of endocarditis has become more complicated as a result of antibiotic resistance. Over the past few years, especially as antibiotics have been overprescribed, more and more strains of bacteria have become increasingly resistant to a wider range of antibiotics. For this reason, doctors may need to try a few different types of antibiotics—or even a combination of antibiotics—to successfully treat the infection. Antibiotics are usually given for about one month, but may need to be given for an even longer period of time if the infection is resistant to treatment.
Once the fever and the worst of the symptoms have gone away, the patient may be able to continue antibiotic therapy at home. During this time, the patient should make regular visits to the health care team for further testing and physical examination to make sure that the antibiotic therapy is working, that it is not causing adverse side effects, and that there are no complications such as emboli or heart failure. The patient should alert the health-care team to any symptoms that could indicate serious complications: For instance, trouble breathing or swelling in the legs could indicate congestive heart failure. Headache, joint pain, blood in the urine, or stroke symptoms could indicate an embolus, and fever and chills could indicate that the treatment is not working and the infection is worsening. Finally, diarrhea, rash, itching, or joint pain may suggest a bad reaction to the antibiotics. Anyone experiencing any of these symptoms should alert the health care team immediately.
In some cases, surgery may be needed. These include cases of congestive heart failure, recurring emboli, infection that doesn't respond to treatment, poorly functioning heart valves, and endocarditis involving prosthetic (artificial) valves. The most common surgical treatment involves cutting away (debriding) damaged tissue and replacing the damaged valve.

Key terms

Aortic valve — The valve between the left ventricle of the heart and the aorta.
Bacteremia — An infection caused by bacteria in the blood.
Congestive heart failure — A condition in which the heart muscle cannot pump blood as efficiently as it should.
Echocardiography — A diagnostic test using reflected sound waves to study the structure and motion of the heart muscle.
Embolus — A bit of foreign material, such as gas, a piece of tissue, or tiny clot, that travels in the circulation until it becomes lodged in a blood vessel.
Endocardium — The inner wall of the heart muscle, which also covers the heart valves.
Mitral valve — The valve between the left atrium and the left ventricle of the heart.
Osler's nodes — Small, raised, reddish, tender areas associated with endocarditis, commonly found inside the fingers or toes.
Petechiae — Tiny purple or red spots on the skin associated with endocarditis, resulting from hemorrhages under the skin's surface.
Pulmonary valve — The valve between the right ventricle of the heart and the pulmonary artery.
Transducer — A device that converts electrical signals into ultrasound waves and ultrasound waves back into electrical impulses.
Transesophageal echocardiography — A diagnostic test using an ultrasound device, passed into the esophagus of the patient, to create a clear image of the heart muscle.
Tricuspid valve — The valve between the right atrium and the right ventricle of the heart.
Vegetation — An abnormal growth of tissue around a valve, composed of blood platelets, bacteria, and a protein involved in clotting.


If left untreated, infective endocarditis continues to progress and is always fatal. However, if it is diagnosed and properly treated within the first six weeks of infection, the infection can be completely cured in about 90% of the cases. The prognosis depends on a number of factors, such as the patient's age and overall physical condition, the severity of the diseases involved, the exact site of the infection, how vulnerable the microorganisms are to antibiotics, and what kind of complications the endocarditis may be causing.


Some people are especially prone to endocarditis. These include people with past episodes of endocarditis, those with congenital heart problems or heart damage from rheumatic fever, and those with artificial heart valves. Intravenous drug users are also at increased risk. Anyone who falls into a high-risk category should alert his or her health-care professionals before undergoing any surgical or dental procedures. High-risk patients must be treated in advance with antibiotics before these procedures to minimize the risk of infection.



Zaret, Barry L., et al., editors. The Patient's Guide to Medical Tests. Boston: Houghton Mifflin, 1997.


American Heart Association. 7320 Greenville Ave. Dallas, TX 75231. (214) 373-6300. http://www.americanheart.org.
National Heart, Lung and Blood Institute. PO Box 30105, Bethesda, MD 20824-0105. (301) 251-1222. http://www.nhlbi.nih.gov.
Gale Encyclopedia of Medicine. Copyright 2008 The Gale Group, Inc. All rights reserved.


Inflammation of the endocardium.
Synonym(s): encarditis
Farlex Partner Medical Dictionary © Farlex 2012


Inflammation of the endocardium.

en′do·car·dit′ic (-dĭt′ĭk) adj.
The American Heritage® Medical Dictionary Copyright © 2007, 2004 by Houghton Mifflin Company. Published by Houghton Mifflin Company. All rights reserved.


Cardiology Inflammation of the endocardium. See Culture-negative endocarditis, Non-bacterial endocarditis, Subacute bacteria endocarditis.
McGraw-Hill Concise Dictionary of Modern Medicine. © 2002 by The McGraw-Hill Companies, Inc.


Inflammation of the endocardium.
Medical Dictionary for the Health Professions and Nursing © Farlex 2012


(en?do-kar-di'tis) [? + ? + itis, inflammation]
Infection or inflammation of the heart valves or of the lining of the heart. In day-to-day clinical speech, this word is often used to mean “infective endocarditis.” See: infective endocarditis

acute bacterial endocarditis

Abbreviation: ABE
Infective endocarditis with a rapid onset, usually a few days to 2 weeks. The infection is typically caused by virulent organisms such as Staphylococcus aureus, which may rapidly invade and destroy heart valvular tissue and also metastasize to other organs or tissues.
See: ulcerative endocarditis

atypical verrucous endocarditis

An infrequently used term for nonbacterial thrombotic endocarditis.

culture-negative endocarditis

Infective endocarditis produced by organisms that do not quickly or readily grow in blood cultures, usually because their growth is masked by the previous use of antibiotics or because the causative organisms require special culture media or grow slowly in the laboratory. Mycoplasma, Ricksettsia, HACEK (an acronym for Haemophilus, Actinobacillus, Cardiobacterium, Eikenella, Kingella) organisms, and some fungi produce culture-negative endocarditis.
See: infective endocarditis
Enlarge picture

infective endocarditis

Abbreviation: IE
Endocarditis caused by any microorganism, esp. any species of streptococci or staphylococci, and less often by Haemophilus spp. or other HACEK bacteria (e.g., Actinobacillus actinomycetem comitans, Cardiobacterium hominis, Eikenella corrodens, or Kingella kingae), enteric bacteria, ricksettsiae, chlamydiae, or fungi. Traditionally, IE can be categorized as acute if the illness has a fulminant onset; catheter-related if the causative microorganism gains access to the heart from an indwelling line; culture-negative if echocardiograms reveal vegetations and other criteria for the disease are present, but the causative microbes have not been isolated in the laboratory; left-sided if it develops on the mitral or aortic valves; nosocomial if it occurs after 48 hr of hospitalization or an invasive surgical procedure; pacemaker-related if the disease occurs on an implanted pacemaker or cardioverter-defibrillator; prosthetic if it occurs on a surgically implanted heart valve; right-sided if it develops on the tricuspid or pulmonary valves; and subacute if it develops after several weeks or months of anorexia, low-grade fevers, and malaise. The incidence in the U.S. is about 2 to 4 cases per 100,000. Patients who are elderly or have a history of injection drug abuse, diabetes mellitus, immunosuppressing illnesses, aortic stenosis, mitral valve prolapse, or rheumatic heart disease are more likely than others to become infected.


Patients with subacute IE may have vague symptoms, including low-grade fevers, loss of appetite, malaise, and muscle aches. Acutely infected patients often present with high fevers, prostration, chills and sweats, stiff joints or back pain, symptoms of heart failure (esp. if the infection has completely disrupted a heart valve or its tethers), heart block (if the infection erodes into the conducting system of the heart), symptoms caused by the spreading of the infection to lungs or meninges (e.g., cough, headache, stiff neck, or confusion), stroke symptoms, symptoms of renal failure, rashes (including petechiae), or other findings. Signs of the illness typically include documented fevers, cardiac murmurs, or (more rarely) nodular eruptions on the hands and feet (Osler's nodes or Janeway lesions). Cottonwool spots may be seen on the retinas of some affected persons. See: illustration


Blood cultures, esp. if persistently positive, form the basis for the diagnosis of endocarditis. Contemporary criteria for diagnosis also include visual confirmation of endocardial infection (vegetations) by echocardiography, the presence of several other suggestive anomalies (e.g., persistent fevers in a patient who is known to inject drugs or a patient with an artificial heart valve), infective emboli in the lungs or other organs; and characteristic skin findings. Occasionally, a patient who dies of a febrile illness may be found to have infective vegetations on the heart valves at autopsy.


Endocarditis is deadly in about 10% to 25% of patients. Death is most likely to occur in patients who suffer strokes resulting from infected fragments embolizing to the brain and in patients who suffer congestive heart failure. Patients with right-sided endocarditis have a better prognosis than patients with other forms of the disease.


Many patients recover after treatment with prolonged courses of parenteral antibiotics. Some (e.g., those with heart failure or severely injured hearts) may not respond without surgery to replace damaged valves or débride abscesses within the myocardium.

Patient care

During the acute phase of treatment, patients are monitored for signs and symptoms of heart failure (e.g., dyspnea, orthopnea, crackles, dependent edema, changes in the heart murmur, and a postsystolic gallop), cerebral emboli (e.g., paralysis, aphasias, changes in mental status), and embolization to the kidney (e.g., decreased urine output, hematuria); lung involvement (e.g., dyspnea, cough, egophony, hemoptysis, pleuritic pain, or friction rub) or spleen involvement (e.g., left upper quadrant abdominal pain radiating to the left shoulder, abdominal rigidity); and peripheral vascular occlusion (e.g., numbness or tingling, changes in pulses, pallor, and coolness in an extremity). Blood cultures may be taken periodically to monitor the effectiveness of antibiotic therapy. Before the administration of antibiotics, a history of allergies is obtained. Treatment peak and trough drug levels are checked (e.g. when aminoglycoside or vancomycin is given) to maintain therapeutic levels and prevent toxicity. Supportive treatment includes bedrest, sufficient fluid intake to preserve hydration, and aspirin or acetaminophen for fever and aches.

Passive and active limb exercises are used to maintain muscle tone and quiet, diversional activities to prevent excessive physical exertion until a slow, progressive activity program that limits cardiac workload can be established.


The American Heart Association recommends that patients at high risk for endocarditis should receive prophylactic antibiotics prior to many procedures, including dental and periodontal cleanings and extractions, intraligamentary local anesthetic injections, tonsillectomy, adenoidectomy, bronchoscopy with rigid instrument, sclerotherapy for esophageal varices, esophageal stricture dilation, biliary tract procedures, barium enema or colonoscopy, surgery involving the respiratory or intestinal mucosa, prostate surgery, cystoscopy, and urethral dilation.

Libman-Sacks endocarditis

See: Libman-Sacks endocarditis

Löffler's endocarditis

See: Löffler's endocarditis

malignant endocarditis

1. An old term for endocarditis that is rapidly fatal.
2. Valvular vegetations composed of tumor cells.

mural endocarditis

Endocarditis of the lining of the heart but not the heart valves.

native valve endocarditis

Infective endocarditis occurring on a patient's own heart valve(s), rather than on a prosthetic (surgically implanted) valve(s).

nonbacterial thrombotic endocarditis

Abbreviation: NBTE
The presence on the heart valves of vegetations that are produced not by bacteria but by sterile collections of platelets in fibrin. NBTE is characteristically found in severe cases of systemic lupus erythematosus, tuberculosis, or malignancy. The vegetations of NBTE readily embolize, causing infarctions in other organs. Synonym: verrucous endocarditis

prosthetic valve endocarditis

Bacterial infection of a surgically implanted artificial heart valve.

rheumatic endocarditis

Valvular inflammation and dysfunction (esp. mitral insufficiency) occurring during acute rheumatic fever.

right-sided endocarditis

Endocarditis affecting the tricuspid or pulmonary valve. It is usually the result of a percutaneous infection and is most often seen in injection drug users.

subacute bacterial endocarditis

Abbreviation: SBE
A heart valve infection that becomes clinically evident after weeks or months. It usually results from infection with streptococcal species that have relatively low virulence (e.g., viridans group streptococci). The infection often develops on a previously abnormal heart valve. Synonym: endocarditis viridans

syphilitic endocarditis

Endocarditis due to syphilis having extended from the aorta to the aortic valves.

tuberculous endocarditis

Endocarditis caused by Mycobacterium tuberculosis.

ulcerative endocarditis

A rapidly destructive form of acute bacterial endocarditis characterized by necrosis or ulceration of the valves.

valvular endocarditis

Endocarditis affecting the heart valves and not the inner lining of the heart.

vegetative endocarditis

Endocarditis associated with fibrinous clots on ulcerated valvular surfaces.

verrucous endocarditis

Nonbacterial thrombotic endocarditis.

endocarditis viridans

Subacute bacterial endocarditis.
Medical Dictionary, © 2009 Farlex and Partners


Inflammation of the inner lining of the heart and of the heart valves, from infection, immune system disturbances or the effect of the death of overlying muscle from CORONARY THROMBOSIS. Heart valve damage from previous RHEUMATIC FEVER, congenital heart disease, the presence of artificial heart valves or damage from cardiac catheters all predispose to the condition. Intravenous drug abusers are also extremely prone to develop infective endocarditis. Without effective treatment infective endocarditis is usually progressive and the condition is rapidly fatal.
Collins Dictionary of Medicine © Robert M. Youngson 2004, 2005


Inflammation of the endocardium.
Medical Dictionary for the Dental Professions © Farlex 2012