What Is Subacute Bacterial Endocarditis?

Medically Reviewed by James Beckerman, MD, FACC on September 04, 2023
Written by WebMD Editorial Contributor
4 min read

Subacute bacterial endocarditis is a type of infective endocarditis. It's an infection that occurs when germs such as bacteria enter the bloodstream and attack the lining of the heart valves. This causes growths, called vegetations, on the heart valves.

Vegetations can cause holes in the valves and cause the infection to spread outside of the heart and blood vessels. Endocarditis is fatal without treatment.

Infective endocarditis can be either acute or subacute. Acute infective endocarditis can develop suddenly and become life-threatening within days. Subacute infective endocarditis develops slowly over a period of several weeks to several months. 

Your heart valves are not supplied directly with blood. Your immune system fights infection with white blood cells that are in your bloodstream. These cells can't reach your heart valves. That makes it difficult to fight the infection, either with your immune system or with antibiotics that travel through the bloodstream.   

Subacute bacterial endocarditis is often caused by a particular group of streptococci bacteria that usually live in your mouth and throat. Normally, your immune system destroys any harmful bacteria that enter your bloodstream. Under certain circumstances, these bacteria can cause endocarditis.

Symptoms of subacute bacterial endocarditis typically develop slowly and may be different for each person. 

Some common symptoms of endocarditis may include:

‌Less common symptoms of endocarditis can include:

  • Unexplained weight loss
  • Blood in your urine
  • Red spots on the soles of your feet or the palms of your hands 
  • Red, tender spots under the skin of your fingers or toes
  • Tenderness in your spleen, which is located just below the ribs on your left side
  • Tiny purple or red spots on your skin, in the whites of your eyes, or inside your mouth

People who have the following issues are more at risk for developing bacterial endocarditis:

  • Heart valve diseases
  • Artificial heart valve
  • Had bacterial endocarditis in the past
  • Heart defects that were present at birth
  • Rely on a pacemaker or similar device
  • Suppressed immune system
  • Intravenous (IV) drug user
  • Hypertrophic cardiomyopathy (HCM), which is when your heart muscle is abnormally thick

Your doctor will listen to your symptoms, review your medical history, and do a physical exam. You may also need additional testing which may include the following.  

Blood cultures. Blood samples are drawn over 24 hours and tested to see if specific bacteria are present in your blood. This will help identify the type of bacteria and help your doctor determine the best antibiotic to treat it. 

Echocardiogram. This test uses sound waves to help your doctor visualize your heart. It will show any abnormalities such as growths, abscesses, or damage to your heart. This may be done with a tube inserted through your mouth so that the pictures can be taken from right behind the heart.

Serological tests. These blood tests check for evidence of infection by seeing if your immune system is showing increased activity. This may be needed if the blood cultures don't show any signs of bacteria.

Antibiotics. Subacute bacterial endocarditis is treated with high doses of intravenous (IV) antibiotics. You will probably have to spend a week or so in the hospital to make sure that your antibiotics are working. After that, you may be able to continue IV antibiotics at home or in your doctor's office. You'll probably need to take antibiotics for several weeks to completely clear up the infection.

Surgery. You may need heart valve surgery to treat endocarditis that won't respond to antibiotics alone. Your heart valve may have to be replaced if it was damaged by the endocarditis.

Subacute bacterial endocarditis can cause complications as a result of the vegetations breaking off and traveling to other parts of your body. Some of these include: 

You can help prevent subacute bacterial endocarditis by taking the following steps.

Take good care of your teeth and gums. Brush and floss your teeth daily and get regular dental care. Subacute bacterial endocarditis is usually caused by bacteria that live in your mouth and throat. Poor dental hygiene may allow the bacteria to get into your bloodstream. 

Understand the symptoms of endocarditis. Call your doctor immediately if you develop any of the symptoms of subacute bacterial endocarditis. This could be a fever that won't go away, unexplained tiredness, skin infections, or cuts or sores that won't heal. 

Don't use intravenous drugs. IV drug use is a big risk factor for developing endocarditis. Dirty needles can carry bacteria directly into your bloodstream.