Some people are more likely than others to develop endocarditis. The following conditions increase the risk:

• a history of rheumatic fever or rheumatic heart disease
• a history of endocarditis
• a congenital (present at birth) heart defect
• prosthetic (artificial) heart valves
• a history of intravenous drug use
• mitral valve prolapse (MVP)
• diabetes
• poor dental hygiene or dental infection
• chronic hemodialysis
• coagulation disorders (e.g., antiphospholipid antibody syndrome)

Endocarditis develops in the endocardium, the inner tissue of the heart. It starts if this tissue has been damaged, injured, or infected. Much as a cut on the skin causes a scab to form, damage to the endocardium can lead to the formation of a blood and tissue clot (thrombus).

In acute infective endocarditis, the clots are caused by bacterial or fungal infection, inflaming and damaging the heart cells. The infection reaches the heart through blood that's carrying a concentration of bacteria, a condition called bacteremia. Once the infectious agent reaches the heart via the blood, it tends to concentrate around the valves – the blood’s point of entry and exit.  Despite the name, infective endocarditis isn't contagious.

The infecting agent can get into the blood through:

• dental work and surgery
• an infected cut on the skin
• injecting drugs into veins
• being fitted with artificial heart valves
• a surgically implanted vascular access device (e.g., a PICC line, Hickman line, or Port-a-Cath)

In non-infective endocarditis, the clot may not be infected but interferes with heart valve function anyway. Some conditions make the formation of scar tissue on the heart valves more likely:

• congenital heart valve disease
• systemic lupus erythematosus (an autoimmune disease)
• chronic infections like tuberculosis and pneumonia
• lung cancer
• having had a previous bout with rheumatic fever

Endocarditis can start slowly and gradually, over the course of several months. This is called subacute infective endocarditis. Symptoms include:

• running a low-grade fever (less than 39.5°C or 103°F)
• muscle and joint aches and pains
• weight loss
• weakness
• night sweats
• nausea
• lack of appetite

If the disease goes untreated for some time, further symptoms may appear:

• red spots on the hands and feet
• red eyes
• clubbed fingernails and toenails
• heart murmurs
• paleness (pallor), especially in extremities

tiny blood clots under the finger or toenails (splinter hemorrhages)At other times, infection progresses very quickly. This is known as acute endocarditis, and causes:

• high fever
• chills
• shortness of breath
• rapid or irregular heartbeat
• coughing up of blood
• abdominal pain
• septicemia (system shock caused by a general infection)

Although most people with infectious endocarditis have a fever, older people and those with long-lasting (chronic) conditions like kidney disease or congestive heart failure may not.

Only your doctor can diagnose endocarditis. The heart test known as an echocardiogram is the main tool for diagnosing endocarditis. For an echocardiogram, a special gel is spread on your chest and a transducer (a device that emits high frequency waves) is put on the chest and moved around. The waves put out by the transducer bounce off different structures in your heart and allow the doctor to see your heart and how it is functioning. Another type of echocardiogram, a transesophageal echocardiogram or TEE, is performed by passing a tube through the esophagus, or food pipe, to take close-up pictures of the heart valves.

If endocarditis is found, you'll need blood tests to identify any bacteria or fungi. This is vital because the treatment for non-infective endocarditis is different than for infective endocarditis.

If a bacterium is causing endocarditis, your doctor will prescribe one or more antibiotics for 2 to 8 weeks. These antibiotics often have to be given by intravenous (IV) injection. If a fungus is the cause, an antifungal medication is given. These must usually be given by IV injection for 6 or more weeks. Heart surgery is sometimes needed for infective endocarditis, especially for people with prosthetic heart valves.

Non-infective endocarditis is treated with anticoagulants like warfarin* that help prevent further clots from developing.

To prevent infective endocarditis, be sure to let your doctor know if you have a prosthetic valve, have previously had endocarditis or have congenital heart disease. This is important especially if you need to undergo surgery or dental work. If you are at a high risk for endocarditis, you may be prescribed antibiotics before surgery or dental work to reduce the risk of endocarditis, depending on the type of procedure you will be undergoing. It is extremely important to take these antibiotics as directed by your doctor.

Currently, recommended preventative antibiotics for dental procedures include:

• amoxicillin 2 g for adults, or 50 mg/kg for children, taken by mouth one hour before a dental procedure.
• for adults and children allergic to penicillin, clindamycin 600 mg for adults, or 20 mg/kg for children, taken by mouth one hour before a procedure. Additional options include clarithromycin or azithromycin 500 mg for adults or 15 mg/kg for children taken by mouth one hour before a procedure.

There are some other preventive measures you can take:

• Taking proper care of your teeth and gums is the single most important preventive measure you can take. The mouth is a common source of bacteria that can cause infection. Good oral hygiene cuts down on the number of bacteria in the mouth and body overall.
• Watch for signs of bacterial infection if you're experiencing symptoms of the common cold or influenza (the flu). Early treatment of more minor ailments can go a long way to reducing the risk of endocarditis.