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Medically reviewed by Last updated on Mar 14, 2023.

What is Endocarditis?

Harvard Health Publishing

Endocarditis, also called infective endocarditis, is an infection and inflammation of the heart valves and the inner lining of the heart chambers, which is called the endocardium. Endocarditis occurs when infectious organisms, such as bacteria or fungi, enter the bloodstream and settle in the heart. In most cases, these organisms are streptococci (andquot;strep"), staphylococci (andquot;staph") or species of bacteria that normally live on body surfaces.

The infecting organism enters the bloodstream through a break in the skin caused by a skin disorder or injury; a medical or dental procedure; or a skin prick, especially among intravenous drug users.

Depending on the aggressiveness (virulence) of the infecting germ, the heart damage caused by endocarditis can be swift and severe (acute endocarditis) or slower and less dramatic (subacute endocarditis).

  • Acute endocarditis - Acute endocarditis most often occurs when an aggressive species of skin bacteria, especially a staphylococcus, enters the bloodstream and attacks a heart valve. Usually the affected heart valve was previously normal. Once staph bacteria begin to multiply inside the heart, they may send small clumps of bacteria called septic emboli into the bloodstream. The septic emboli enter other organs, especially the kidneys, lungs and brain. Intravenous (IV) drug users are at very high risk of acute endocarditis, because numerous needle punctures give aggressive staph bacteria many opportunities to enter the blood through broken skin. Dirty drug paraphernalia increases the risk. If untreated, this form of endocarditis can be fatal in less than six weeks.
  • Subacute endocarditis - This form of endocarditis most often is caused by one of the viridans group of streptococci (Streptococcus sanguis, mutans, mitis or milleri) that normally live in the mouth and throat. Streptococcus bovis or Streptococcus equinus also can cause subacute endocarditis, typically in patients who have a gastrointestinal problem, such as diverticulitis or colon cancer. Subacute endocarditis tends to involve heart valves that are abnormal, such as narrowed or leaky heart valves. Subacute bacterial endocarditis often causes non-specific symptoms that can persist for many weeks before a diagnosis is made.

Men develop endocarditis more often than women, and the illness is more common among people who have one or more of the following risk factors:

  • A congenital (present at birth) malformation of the heart or a heart valve, or mitral valve prolapse with mitral valve regurgitation
  • A heart valve damaged by rheumatic fever or by age-related valve thickening with calcium deposits
  • An implanted device in the heart (pacemaker wire, artificial heart valve)
  • A history of IV drug use

In about 20% to 40% of patients who do not have artificial heart valves and who do not use intravenous drugs, no heart problem can be identified that would increase their risk of endocarditis. In the 10% to 20% of endocarditis patients who have artificial heart valves, infections that follow within 60 days of valve surgery often are caused by a staphylococcus, while endocarditis that occurs later most frequently is caused by a streptococcus.


Symptoms of acute endocarditis include:

  • High fever
  • Chest pain
  • Shortness of breath
  • Cough
  • Extreme fatigue

Symptoms of subacute endocarditis include:

  • Low-grade fever (less than 102.9 degrees Fahrenheit)
  • Chills
  • Night sweats
  • Pain in muscles and joints
  • A persistent tired feeling
  • Headache
  • Shortness of breath
  • Poor appetite
  • Weight loss
  • Small, tender nodules on the fingers or toes
  • Tiny broken blood vessels on the whites of the eyes, the palate, inside the cheeks, on the chest, or on the fingers and toes


Your doctor will review your medical history with particular attention to possible risk factors for endocarditis, including congenital heart disease, rheumatic fever, an artificial heart valve or pacemaker, a history of IV drug use, and a history of chronic illness. Your doctor also will ask whether you have ever been told that you have a heart murmur and whether you have had any recent medical or dental procedure in which bacteria might have had an opportunity to entire your bloodstream (dental scaling, periodontal surgery, professional teeth cleaning, bronchoscopy, certain diagnostic tests of the genitourinary tract, colonoscopy).

Your doctor will examine you, and will check for fever; skin symptoms of endocarditis (tiny hemorrhages in the skin, tender nodules on finger and toes); and a heart murmur, which indicates possible heart valve damage. Additional testing includes:

  • Blood cultures - In these tests, several blood samples will be drawn over a 24-hour period. These blood samples will be added to culture bottles that contain special nutrients to aid bacterial growth. If bacteria are living in your bloodstream, they will grow inside the culture bottles in the laboratory. Once bacteria grow, the specific species can be identified, and it can be tested for its sensitivity to various types of antibiotics. Results of this testing will help your doctor select the specific antibiotic that will work best to treat endocarditis.
  • Echocardiography - In this test, sound waves are used to outline the structure of the heart, the heart chambers and heart valves. By using echocardiography, your doctor can check for abnormal growths that contain infecting organisms (vegetations) inside the heart. He or she also can look for abscesses inside the heart and for signs of damage to natural or artificial heart valves. The best type of echocardiography for evaluating heart valves is transesophageal echocardiography, in which a tube is inserted through your mouth, allowing images of the heart to be obtained from just behind it. This test may be recommended if the diagnosis remains uncertain after conventional echocardiography. Transesophageal echocardiography is also a much better test for evaluating artificial heart valves.
  • Serological tests - These are blood tests that look for evidence of increased immune system activity, which is a sign of infection. These tests may be helpful when blood cultures do not show bacterial growth, which happens in a small percentage of patients.

Expected duration

Symptoms of acute endocarditis usually begin suddenly and get worse quickly. It is an infection that can develop dramatically over a few days. Subacute endocarditis develops more slowly, and its milder symptoms can be present for weeks or months before the illness is suspected.


If you are at high risk of endocarditis because of a damaged heart valve or other medical problem, tell your doctor and dentist. To prevent endocarditis, your doctor and dentist may prescribe antibiotics before you have any medical or dental procedure in which bacteria have a chance of entering your blood. This is called prophylactic antibiotics.

Prophylactic antibiotics usually are given to people with artificial valves, people who had endocarditis in the past and people with other high-risk conditions. Most people with mitral valve prolapse and other minor abnormalities of heart structure do not need antibiotics before medical or dental procedures.

In general, antibiotics are given one to two hours before a high-risk procedure, and up to eight hours afterward. Before a dental procedure, an antiseptic mouth rinse also can be used, especially one containing chlorhexidine or povidone-iodine.

You also can help to prevent endocarditis by avoiding IV drug use.


When endocarditis is caused by a bacterial infection, it usually is treated with four to six weeks of antibiotics.  The type of antibiotic and the length of therapy depend on the results of the blood cultures. Antibiotic treatment is given intravenously (through a vein). Treatment is almost always started while you are in the hospital. When your doctor determines it is safe, you can be discharged home to finish the course of intravenous antibiotics. 

Sometimes the infected heart valve must be replaced surgically. Indications for surgery may include:

  • Damage to a heart valve that is severe enough to cause heart failure unresponsive to medical therapy
  • Backflow of blood through the aortic or mitral valve (regurgitation) that is severe and unresponsive to medical therapy
  • Formation of an abscess around a heart valve
  • Endocarditis caused by an organism not responding to antibiotics. For example, fungal endocarditis often responds poorly to intravenous antifungal medications
  • Abnormal growth of organisms (vegetation) larger than 10 millimeters (seen on echocardiography) clinging to a heart valve and not shrinking with antibiotic therapy
  • Recurrent embolization from pieces of the vegetation that continue to break away from the heart valve, enter the blood stream and get lodged in other organs. For example, recurrent strokes from emboli to the brain.

Treatment options

The following list of medications are in some way related to or used in the treatment of this condition.

View more treatment options

When to call a professional

Call your doctor whenever you experience symptoms of acute or subacute endocarditis, especially if you have a history of heart valve damage, a known heart murmur or an implanted device in your heart (artificial valve or pacemaker wire).


With prompt diagnosis and proper medical treatment, over 90% of patients with bacterial endocarditis recover. Those whose endocarditis affects the right side of the heart tend to have a better outlook than those with left-side involvement. In cases in which endocarditis is caused by fungi, the prognosis is usually worse than for bacterial endocarditis.

Some possible complications of endocarditis include:

  • Congestive heart failure
  • Floating blood clots, called emboli, in the bloodstream that lodge in the brain, lungs or coronary arteries
  • Kidney problems

If endocarditis remains untreated, it can cause severe permanent disability and death.

Additional info

American Heart Association (AHA)

National Heart, Lung, and Blood Institute (NHLBI)

American College of Cardiology

Learn more about Endocarditis

Treatment options

Care guides

Further information

Always consult your healthcare provider to ensure the information displayed on this page applies to your personal circumstances.