Endocarditis describes any inflammation of the interior layers of heart tissue (the endocardium), including the heart valves. These tissues are special in that they contain no capilliaries, the blood instead being supplied to the muscles in the rest of the heart through the coronary artery. Although there are limited ways that these tissues can become inflamed, because they have no dedicated blood supply, once inflammation occurs it is slow to heal and difficult to treat. Endocarditis is usually detected with an echocardiogram.
There are two general causes of endocarditis:
- Infection - Although the endocardium is smooth (including artificial replacement valves) and therefore difficult for infection to lodge in the area, when there is slight damage to the tissues, infections can grow in the endocardium and form vegetations. Because it becomes impossible for the body to target white blood cells to the area the infection and inflammatory response can continue unabated. Medication is similarly ineffective against such an infection because of the lack of a dedicated blood supply to the area. Often, these vegetations have to be removed with surgery.
- Clotting - Even on undamaged tissue, if there is a systemic infection or coagulopathy, clots can form on the tissues of the endocardium. Although the individual vegetations are small, there are several of them and they tend to be in specific areas, particularly along the edges of surfaces. These clots can break off and cause infarctions elsewhere in the body.
Treating the underlying infection will usually improve the endocarditis. Not all infections can cause endocarditis, and even some that do will not show up in blood cultures. As such, endocarditis is not of much help in a differential diagnosis to identify an infection.