Infectious endocarditis is an infection of the lining of the heart chambers and heart valves, caused by bacteria, fungi, or other infectious agents.

Infectious endocarditis is an inflammation of the heart valves. Endocarditis is distinguished from infections of heart muscle (myocarditis) or the lining of the heart (pericarditis). Most people who develop infectious endocarditis have underlying heart disease.

Endocarditis is usually a result of bacteremia (bacteria in the blood), which is common during dental, upper respiratory, urologic, and lower gastrointestinal diagnostic and surgical procedures. The bacteria in the bloodstream can settle on damaged heart valves, and grow to create a “vegetation” or clump of live bacteria. These growths may form infected clots that break off and travel to the brain, lungs, kidneys, or spleen.

Many bacteria can cause endocarditis in patients with underlying valve problems, but an organism commonly found in the mouth, Streptococcus viridans, is responsible for approximately half of all bacterial endocarditis. Other common organisms include Staphylococcus aureus and enterococcus. Less common organisms include pseudomonas, serratia, and candida. Staphylococcus aureus can infect normal heart valves, and is the most common cause of infectious endocarditis in intravenous drug users.

Symptoms of endocarditis may develop slowly (subacute) or suddenly (acute). Fever is a hallmark of both. In the slower form, fever may be present on a daily basis for months before other symptoms appear. Other symptoms are nonspecific, such as fatigue, malaise (general discomfort), headache, and night sweats. As the illness progresses, small dark lines, called splinter hemorrhages, may appear under the fingernails.

The health care provider may hear changing murmurs in the heart and detect an enlarged spleen and mild anemia. Murmurs result from changes in blood flow across valves when clumps of bacteria, fibrin and cellular debris, called vegetations, collect on the heart valves. The mitral valve is most commonly affected, followed by the aortic valve.

Preexisting conditions that increase the likelihood of developing endocarditis include:

• Congenital (present at birth) heart disease (atrial septal defect, patent ductus arteriosus, and others)
• Prior rheumatic heart disease
• Cardiac valve anomalies (such as mitral insufficiency)
• Artificial heart valves

Since Streptococcus viridans is often found in the mouth, dental procedures are the most common cause of bacterial endocarditis. This can put children with congenital heart conditions at risk. As a result, it is common practice for children with some forms of congenital heart disease, and adults with certain heart-valve conditions to start on antibiotics prior to any dental work.

• Fatigue
• Weakness
• Fever
• Chills
• Night sweats (may be severe)
• Weight loss
• Muscle aches and pains
• Heart murmur
• Shortness of breath with activity
• Swelling of feet, legs, abdomen
• Blood in the urine
• Excessive sweating
• Red, painless skin spots on the palms and soles (Janeway lesions)
• Paleness
• Nail abnormalities (splinter hemorrhages under the nails)
• Joint pain
• Abnormal urine color
• Red, painful nodes (Osler's nodes) in the pads of the fingers and toes

A history of congenital heart disease raises the level of suspicion. A physical examination may show an enlarged spleen. The examiner may detect a new heart murmur, or a change in a previous heart murmur. Examination of the nails may show splinter hemorrhages. Eye examination may show retinal hemorrhages with a central area of clearing, called Roth's spots.

The following tests may be performed:

• Repeated blood culture and sensitivity (#1 test for detection)
• ESR (erythrocyte sedimentation rate)
• CBC (complete blood count) may show low grade, microcytic (small red blood cells) anemia
• Echocardiogram
• Transesophageal echocardiogram
• Chest x-ray
• CT scan of the chest

Hospitalization is required initially to administer intravenous antibiotics. Long-term, high-dose antibiotic trearment is required to eradicate the bacteria from the vegetations on the valves. Treatment is usually administered for 4-6 weeks, depending on the organism. The chosen antibiotic must be specific for the organism causing the condition. This is determined by the blood culture and the sensitivities tests.

If heart failure develops as a result of damaged heart valves, surgery to replace the affected heart valve may be needed.

Early treatment of bacterial endocarditis generally has a good outcome. Heart valves may be damaged if diagnosis and treatment are delayed.

• Congestive heart failure if treatment is delayed
• Blood clots or emboli that travel to brain, kidneys, lungs, or abdomen, causing severe damage
• Arrhythmias (rapid or irregular heartbeat), such as atrial fibrillation
• Glomerulonephritis
• Severe valve damage
• Stroke
• Brain abscess
• Neurologic changes
• Jaundice

Call your health care provider if you note the following symptoms during or after treatment:

• Weight loss without change in diet
• Blood in urine
• Chest pain
• Weakness
• Numbness or weakness of muscles
• Fever

Preventive antibiotics are often given to people at risk for infectious endocarditis before dental procedures or surgeries involving the respiratory, urinary, or intestinal tract. Continued medical follow-up is recommended for people with a previous history of infectious endocarditis.

Intravenous drug users are also at risk for this condition, because unsterile injecting practices increase the exposure of the bloodstream to infectious agents. Treatment for addiction should be sought. If this is not possible, use of a new needle for each injection, avoiding sharing any injection-related paraphernalia, and use of alcohol pads to sterilize the injection site can reduce risk.