Bacterial endocarditis

Infective Endocarditis, Acute Bacterial or Subacute Bacterial Endocarditis

What is Bacterial endocarditis?

Bacterial endocarditis is an inflammation of the inner lining of the heart (endocardium) and particularly the heart valves, due to infection. Infection may also occur at the site of a septal defect (birth defect in which there is a hole between the left and right sides of the heart), on the chordae tendineae (small tendons attached to the heart valves), or in the endocardium itself. Endocarditis may occur alone or as a complication of another disease. The infection can be caused by any number of microorganisms. It is classified as acute or subacute. The incidence of bacterial endocarditis increases with age. Men have a higher incidence than females.

Bacterial endocarditis is seen most often when the endocardium has already been damaged by rheumatic heart disease, congenital heart disease, mitral valve prolapse, mitral valve insufficiency, or in individuals with prosthetic heart valves. Clots that have formed on the injured surfaces trap microorganisms entering the bloodstream. These microorganisms multiply rapidly, causing inflammation and further damage. Bacteria may enter the bloodstream during surgery, major dental treatment (especially tooth extraction), or exploratory procedures where a viewing tube is inserted into the body for diagnostic examination. Intravenous drug users are also at increased risk for bacterial endocarditis because of the possibility of introducing bacteria from a dirty syringe or unclean injection site directly into the blood stream.

Acute bacterial endocarditis refers to an inflammation with an abrupt onset. The infection progresses quickly and may destroy the heart valves, leading rapidly to progressive heart failure. In addition, clots attached to the damaged valves tend to break apart. These fragments of infected tissue are carried through the blood where they may block an artery (embolism) or spread infection to other parts of the body. Damage to valves and spread of the infection to other body areas occurs in a few days to several weeks. Acute bacterial endocarditis is most often caused by the staphylococci organism.

Subacute bacterial endocarditis refers to an inflammation that smolders undetected over several weeks to many months. Although it can cause serious damage to the heart valves, there is minimal spread to other areas of the body. The subacute form of bacterial endocarditis is most often caused by viridans streptococci, enterococci, and coagulase negative staphylococci organisms.

How is it diagnosed?

Bacterial Endocarditis signs and symptoms

Early symptoms:

  • Fatigue and weakness.
  • Intermittent fever, chills and excessive sweating, especially at night.
  • Weight loss.
  • Vague aches and pains.
  • Heart murmur.

Late symptoms:

  • Severe chills and high fever.
  • Shortness of breath on exertion.
  • Swelling of the feet, legs and abdomen.
  • Rapid or irregular heartbeat.

History: Acute bacterial endocarditis comes on suddenly. Symptoms include high fever, severe chills, cough, and shortness of breath. In subacute bacterial endocarditis, the symptoms are general and nonspecific, such as fatigue, weakness, night sweats, or vague aches and pains. Fever may be low-grade, or absent in elderly and debilitated persons.

Physical exam reveals fever, rapid or irregular heartbeat, and numerous small, flat, red to blue spots (petechiae) on the conjunctiva (lining of the eye), the arms and legs, and the mucous membranes of the mouth and throat. Dark, red, linear streaks (splinter hemorrhages) may be present in the nailbeds, accompanied by small, raised, tender blue or red areas in the pads of the fingers or toes (Osler's nodes). Exam may also reveal joint pain, muscle pain, and a heart murmur (new or changed).

Tests: Blood cultures are used both for diagnosis, sensitivity to antibiotics, and for following the response to therapy. Examination of tissue growth (vegetations) on the valves may also be done. Additional diagnostic laboratory tests include complete blood count (CBC), sedimentation rate, blood studies (serology), and urinalysis. Evaluation of the heart may include detecting abnormal valve function or heart disease through echocardiogram (procedure in which an image of the heart is obtained by using sound waves), examining the electrical patterns of the heart through electrocardiogram (EKG), and angiography (x-ray of blood vessels after injection with contrast medium).

How is Bacterial endocarditis treated?

Treatment involves high doses of antibiotics given intravenously over a four to six week period. If infection has extensively damaged a heart valve, it may need to be surgically replaced with an artificial one. When an artificial heart valve that is already in place becomes infected, it must be replaced. Heart valve replacement often becomes an emergency procedure.

Endocarditis Medication

Antibiotics for many weeks to fight infection. Antibiotic treatment is often intravenous.

Information Brand Generic Label Rating
Zithromax Zithromax Azithromycin On-Label
Flagyl Flagyl Metronidazole On-Label Amoxil Amoxicillin On-Label
Ampicillin 500mg Principen Ampicillin On-Label

Ilosone (Erythromycin), Biaxin (Clarithromycin), Keflex (Cephalexin)


  • Rest in bed until fully recovered. While in bed, flex your legs often to prevent clots from forming in deep veins.
  • Resume your normal activities, including sexual relations, when strength allows.

What might complicate it?

Complications include systemic emboli (blood vessels obstructed by fragments of tissue carried through the bloodstream), tissue death in the spleen (splenic infarction), stroke, brain hemorrhage, congestive heart failure, and kidney failure. The emboli may also be infected, which can lead to sepsis. Additional complications of therapy include infection and thrombophlebitis.

Predicted outcome

Most individuals recover completely. There is a mortality rate of 16% to 25%. The mortality rate increases with age, presence of underlying disease, development of congestive heart failure, or central nervous system complications. There is a 75% to 80% survival rate in individuals with prosthetic heart valves. Depending on the causative organism, relapses occur in two to eight percent of individuals. Most relapses occur within two months after treatment.


Conditions with similar symptoms include acute rheumatic fever with carditis, periarteritis nodosa, poststreptococcal glomerulonephritis, and reaction to drugs.

Appropriate specialists

Cardiologist, infectious disease specialist, and internist.

Last updated 18 December 2011

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