Bacterial Endocarditis

Bacterial endocarditis is a serious infection of the heart’s inner lining and valves that can lead to death if not treated promptly, but with early diagnosis and proper antibiotics, many people survive and recover.

Table of contents

• What is Bacterial Endocarditis?
• How Does the Infection Happen?
• Who is at Risk?
• Signs and Symptoms
• How Doctors Diagnose the Condition
• Treatment Options
• Prevention

What is Bacterial Endocarditis?

Bacterial endocarditis, also called infective endocarditis, is an infection caused by bacteria that enter the bloodstream and settle in the heart lining, heart valves, or a blood vessel.^[1] The heart has four valves that help blood flow through the heart and lungs and out to the body. When a person has bacterial endocarditis, these valves may not work correctly, forcing the heart to work harder to get blood out to the body. Sometimes the heart cannot pump out enough blood.^[1]

The infection causes inflammation, which is swelling and irritation of the inner lining of the heart’s chambers and valves. This lining is called the endocardium.^[2] As inflammation continues, the infection creates growths in the heart’s lining called vegetations. These vegetations break down the surrounding heart tissue and can greatly damage the heart valves.^[2]

The vegetations are made of infecting bacteria, fibrin (a protein that plays a role in blood clotting), and platelets (tiny cell fragments in the blood).^[2] These clumps can travel to many other parts of the body and cause problems.^[1]

Bacterial endocarditis is uncommon, but it is a serious condition that can sometimes lead to death, especially if not treated right away.^[1] In developed countries, the incidence of endocarditis ranges from 2.6 to 7 cases per 100,000 people per year.^[3] In adults, bacterial endocarditis is more common in men than in women. In fact, twice as many men are affected as women.^[6]

• Heart valves
• Endocardium (inner lining of heart chambers)

How Does the Infection Happen?

Some kinds of bacteria normally live on and in the body. They live in the mouth, in the respiratory system, on the skin, and in the digestive tract.^[1] Sometimes these bacteria can get into the bloodstream. This may happen after a medical or dental procedure that breaks the skin or other tissue. The bacteria go into the bloodstream and can settle on the heart lining or on the heart valves.^[1]

Bacteria enter the bloodstream from the skin, mucosal surfaces, or previously infected sites and attach to areas of the heart where there is damage or abnormality.^[3] Healthy heart tissue is normally very resistant to infection. But underlying damage can make it more likely for endocarditis to develop. The bacteria attach to and grow on damaged tissue. They grow vegetations and produce enzymes that destroy surrounding heart tissue.^[2]

Not all types of bacteria can cause this kind of infection, but many types can. Two kinds of bacteria cause most cases of bacterial endocarditis. These are staphylococci (staph) and streptococci (strep).^[1] Most cases are caused by viridans streptococci, Streptococcus gallolyticus, Staphylococcus aureus, coagulase-negative staphylococci, HACEK organisms (Haemophilus, Aggregatibacter, Cardiobacterium, Eikenella, Kingella), and enterococci.^[3]

In some cases, the symptoms start suddenly and are severe. This is called acute bacterial endocarditis. It begins suddenly with a high fever and fast heart rate and can become life-threatening within days.^[2] In other cases, it happens more slowly and is less severe. This is called subacute bacterial endocarditis. It develops gradually over weeks or several months.^[2]

Who is at Risk?

Bacterial endocarditis can occur in any person who has heart disease present at birth, also called congenital heart disease, or can occur in people without heart disease.^[5] However, it is uncommon for a person with a normal heart to get endocarditis.^[1]

You may be at increased risk for bacterial endocarditis if you have certain heart valve defects. This gives the bacteria an easier place to take hold and grow.^[1] People with congenital heart disease may have abnormal inner heart linings due to thickened valves that cause abnormal opening or leaking of the valve. Even after surgery, roughened areas may remain due to scar tissue formation or surgical patches used to redirect blood flow. These rough areas inside the heart are ideal places for bacteria to build up and multiply.^[5]

Risk factors that may increase the chance of getting bacterial endocarditis include:^[1]

• IV (intravenous) drug use
• Hemodialysis for kidney failure
• Heart valve disease, such as leaking or narrowed valve
• Rheumatic heart disease caused by strep bacteria
• Implantable cardiac device
• Heart disease present at birth (congenital)
• Past history of endocarditis
• Poor dental hygiene
• Artificial heart valves or valve repair or replacement
• Heart transplant with a leaky heart valve
• Weak immune system

Additional risk factors include age greater than 60 years, male gender, and the presence of an indwelling intravenous catheter.^[3] Diabetes also increases the risk.^[2]

Signs and Symptoms

Symptoms of bacterial endocarditis can vary from person to person. Endocarditis may develop slowly or suddenly. It depends on the type of germs causing the infection and whether there are other heart problems.^[4] A common sign of bacterial endocarditis is prolonged fever for two to three days in patients with congenital heart disease, particularly after a dental, intestinal, or urinary tract procedure.^[7]

Common symptoms of endocarditis include:^[4]

• Aching joints and muscles
• Chest pain when you breathe
• Fatigue
• Flu-like symptoms, such as fever and chills
• Night sweats
• Shortness of breath
• Swelling in the feet, legs, or belly
• A new or changed whooshing sound in the heart (murmur)
• Fast heart rate
• Loss of appetite and weight loss

Less common symptoms can include:^[4]

• Unexplained weight loss
• Blood in the urine
• Tenderness under the left rib cage (spleen)
• Painless red, purple, or brown flat spots on the soles of the feet or the palms of the hands (Janeway lesions)
• Painful red or purple bumps or patches of darkened skin on the tips of the fingers or toes (Osler nodes)
• Tiny purple, red, or brown round spots on the skin (petechiae), in the whites of the eyes, or inside the mouth
• Rash

If you have symptoms of endocarditis, see your health care provider as soon as possible, especially if you have a history of heart problems or other risk factors. Infective endocarditis is life-threatening and requires immediate medical attention.^[2]

How Doctors Diagnose the Condition

To diagnose endocarditis, a health care provider does a physical exam and asks questions about your medical history and symptoms.^[8] Tests are done to help confirm or rule out endocarditis.

The primary test for bacterial endocarditis is a blood culture test. This test helps identify germs in the bloodstream. Three to five blood samples may be taken in a 24-hour period to determine the presence of the bacteria.^[7] Results from this test help determine the antibiotic or combination of antibiotics to use for treatment.^[8] It is imperative to obtain at least two separate blood cultures from two different venous sites for targeted antibiotic therapy before administering antibiotics.^[12]

Other tests used to help diagnose endocarditis include:^[8]

• Complete blood count: This test can determine if there are a lot of white blood cells, which can be a sign of infection. It can also help diagnose low levels of healthy red blood cells (anemia), which can be a sign of endocarditis.
• Echocardiogram: Sound waves are used to create images of the beating heart. This test shows how well the heart’s chambers and valves pump blood. It can also show the heart’s structure. An echocardiogram may detect an abnormality, such as a mass on a heart valve or on the heart wall surface, called a vegetation.^[7] Two types may be used: a standard (transthoracic) echocardiogram and a transesophageal echocardiogram, which provides much more detailed pictures of the heart.
• Electrocardiogram (ECG or EKG): This quick and painless test measures the electrical activity of the heart. It shows if something is affecting the heart’s electrical activity.
• Chest X-ray: This test can show changes in the heart or lungs.

A urine sample also may indicate the presence of infection but is not adequate by itself for the diagnosis.^[7]

Treatment Options

Most cases of bacterial endocarditis can be treated with antibiotics. You will usually have to be admitted to hospital so the antibiotics can be given through a drip in your arm (intravenously).^[11] The choice of antibiotic therapy for bacterial endocarditis is determined by the identity and antibiotic susceptibility of the infecting organism, the type of cardiac valve involved (native or prosthetic), and characteristics of the patient, such as drug allergies.^[10]

Your doctor will usually take a blood sample before prescribing antibiotics to make sure you are given the most effective treatment. If your symptoms are severe, you may be prescribed a mixture of different antibiotics before getting the result of the blood sample.^[11] While you are in hospital, regular blood samples will be taken to see how well the treatment is working.^[11]

Once your fever and any severe symptoms subside, you may be able to leave hospital and continue receiving antibiotics at home through a drip. Recovery may take four to six weeks, and there is a risk of permanent heart damage.^[7] You will usually have to take antibiotics for 2 to 6 weeks.^[11]

Treatment with aqueous penicillin or ceftriaxone is effective for most infections caused by streptococci. A combination of penicillin or ampicillin with gentamicin is appropriate for endocarditis caused by enterococci. Vancomycin should be substituted for penicillin in patients with a history of immediate-type hypersensitivity to penicillin or when high-level resistance is present.^[10]

Surgery may be needed in some cases. You may need surgery to repair damage to the heart. Surgery will usually be recommended if:^[11]

• Your symptoms or test results suggest you have experienced heart failure
• You continue to have a high temperature (fever) despite treatment with antibiotics or antifungals
• Your endocarditis is caused by particularly aggressive fungi or drug-resistant bacteria
• You experience one or more blood clots despite treatment with antibiotics or antifungals
• You have an artificial (prosthetic) heart valve
• The results of your echocardiogram suggest that a collection of pus (abscess) or an abnormal passageway (fistula) has developed inside your heart

The three main surgical procedures used to treat endocarditis are repair of the damaged heart valve, replacement of the damaged heart valves with prosthetic ones, and draining of any abscesses and repair of any fistulas that may have developed in the heart muscle.^[11] Approximately 50% of patients with endocarditis will require some form of surgical intervention.^[12]

Prevention

Bacterial endocarditis usually can be prevented by taking antibiotics immediately before and after procedures in which bacteria may be released into the bloodstream.^[7] These procedures include:^[7]

• Bronchoscopy
• Dental cleaning
• Gallbladder or prostate surgery
• Some surgeries in the respiratory passageways, or the gastrointestinal or urinary tracts
• Tonsillectomy and adenoidectomy

Now that you have had the infection, you are at risk for getting it again. It is important that you let all your other doctors know that you have had bacterial endocarditis. Let your dentist know too.^[18] In the future, you may have to take antibiotics before certain medical, dental, or surgical procedures. Ask your doctor or dentist about this, and do not have any of these procedures without talking to your doctor or dentist first.^[18]

People at risk for bacterial endocarditis are encouraged to practice good oral hygiene.^[7] Practice good oral hygiene by brushing and flossing your teeth daily and by visiting a dentist twice each year. Make sure your dentist knows that you have had endocarditis.^[18] Maintaining good dental health and gum health is important because bacteria from the mouth can enter the bloodstream.^[2]