Endocarditis is an inflammation of the inner layer of the heart, the endocardium. It usually involves the heart valves (native or prosthetic valves). Other structures that may be involved include the interventricular septum, the chordae tendineae, the mural endocardium, or even on intracardiac devices. Endocarditis is characterized by a prototypic lesion, the vegetation, which is a mass of platelets, fibrin, microcolonies of microorganisms, and scant inﬂammatory cells. In the subacute form of infective endocarditis, the vegetation may also include a center of granulomatous tissue, which may fibrose or calcify.
There are multiple ways to classify endocarditis. The simplest classification is based on etiology: either infective or non-infective, depending on whether a microorganism is the source of the inflammation or not. Regardless, diagnosis of endocarditis is based on the clinical features, investigations such as echocardiogram, as well as any blood cultures demonstrating the presence of endocarditis-causing microorganisms.
Since the valves of the heart do not receive any dedicated blood supply, defensive immune mechanisms (such as white blood cells) cannot directly reach the valves via the bloodstream. If an organism (such as bacteria) attaches to a valve surface and forms a vegetation, the host immune response is blunted. The lack of blood supply to the valves also has implications on treatment, since drugs also have difficulty reaching the infected valve.
Normally, blood flows smoothly through these valves. If they have been damaged (from rheumatic fever, for example) the risk of bacteria attachment is increased.
What causes endocarditis?
An international study showed that infective endocarditis, infection and inflammation involving the heart valves is commonly associated with health care factors and is increasingly due to staphylococcal infection. Another study found that tongue studs raise a person's risk of developing endocarditis.
Normal daily activities, such as eating food, or brushing one's teeth, are opportunities for the bacteria or fungus to enter the human body and cause endocarditis. A dental or medical procedure that result in an infection could also be a cause. If your teeth and/or gums are in bad condition it is easier for the bacteria to get in. A study found that good dental hygiene helps prevent heart infection.
Bacteria that live in your mouth, upper respiratory tract or other parts of your body can cause endocarditis. Normally harmless, these organisms can attack the heart tissue and cause infection.
If an area of your body is already infected bacteria can sometimes spread, e.g. as might happen with a sore on your skin, or a gum disease that makes your gums bleed.
Sexually transmitted diseases, such as Chlamydia or gonorrhea make it easier for bacteria to get in and make their way to your heart.
Inflammatory bowel disease or any intestinal disorders may also increase risk. However, the risk is always very low as endocarditis is a rare condition.
Experts say that people with a heart defect are at much higher risk of developing endocarditis when the bacteria enter the body, especially if they have an abnormal heart valve or damaged heart tissue.