Infective endocarditis is a bacterial infection of the heart’s inner lining or endocardium.

Causes and risk factors

Three major bacteria are suspected to cause this type of infection. These include:

• Streptococci
• Staphylococci
• Enterococci

Since the valves of the heart do not have a blood supply, they are less equipped to fight bacteria than other parts of the heart. Bacteria in the blood passes through the heart and can settle in a damaged valve. Here, the bacteria can establish a vegetation and are well shielded from the body’s immune processes, which fail to combat the infection. The lack of adequate blood supply in this area also means most antibiotics fail to reach the target site and correct the infection.

Risk factors

The risk of endocarditis is increased in the presence of the following factors:

• Damaged heart valves due to diseases such as rheumatic fever
• Artificial or prosthetic heart valves
• Congenital heart disease that may or may not have damaged the heart valves
• The use of heroin or other drugs

Mode of infection

Ways in which bacteria may reach the bloodstream and heart include:

• Via the mouth, through brushing the teeth or chewing foods when the gums are damaged or bleeding, particularly in the presence of gum disease.
• Through an existing infection of the skin or gums
• Through the sexual transmission of an infection such as chlamydia or gonorrhoea
• Via contaminated needles, syringes, catheters, laparoscope and tubes

Symptoms

Some of the initial endocarditis symptoms are flu-like and include fever (temperature at or above 38 degrees celcius), joint and muscle pain and headache. If the infection is not treated, it can damage the heart valves and disrupt the normal flow of blood in the heart. This may lead to complications such as heart failure, where the heart fails to pump blood into the circulation. Stroke is another complication, where blood flow to the brain is disrupted.

Infective endocarditis may develop in two ways:

• Acute endocarditis that develops over the course of a few days
• Subacute endocarditis that develops over a course of a few weeks or months

Treatment

The aim of treatment is to eliminate the bacteria. The patient is administered antibiotics intravenously while in hospital. Around one fifth of those treated for endocarditis will also require surgery to repair heart valves or to drain an abscess. Even when standards of healthcare are very high, the risk of death from endocarditis is about 20%. Early detection and prompt treatment are therefore essential to increase the likelihood of survival.