The inside of the heart is covered by endothelium throughout. Why are valves predisposed to endocarditis? I know it can affect other structires like the septum, chordae etc. But why the valves? Especially bacterial endocarditis.
Wouldn't a place on the ceiling of the atria be quieter and have less turbulence?
Robbin's Pathology says that valves derive nutrition from the surrounding blood and there vessels but mostly on the proximal side. So it might not be due to nutrition.
In the case of Libman Sacks endocarditis (which isn't infective), they can happen anywhere even on the atrial,ventricular endocardium. But still, most commonly they are found on the mitral valves.
Are there theories for this?
For endocarditis to occur on native valves, the valves must be abnormally regurgitant or stenotic to get involved by endocarditis. Stenosis or regurgitation flows are abnormally rapid. These rapid abnormal blood flow jets lead to endothelial injury, non- bacterial or sterile endocarditis (platelets, fibrin threads, RBCS). Then when bacteremia occur due to trauma to skin or mucosal membrane, the bacteria invade these lesions causing baterial endocaritis. The same occurs with congenital shunts like VSD or PDA. That's why IE is less common with pure mitral stenosis or ASD because of the low pressire gradient and the low velocity of the flow jets.
For endocarditis on prosthetic valves, it is a foreign body that is easily to be invaded with bacteria in case of bacteremia.
The native healthy valve that could be involved with IE is the tricuspid valve in cases of drug addicts. Low immunity, lack of sterilization encourages infection, the tricuspid valve is the first structure the bacteria meet after IV injection.
I don't know the reason fr the distribution of Libman Sacks endocarditis.
The heart valves are not supplied directly with blood. Therefore, the body’s immunity response system, such as the infection-fighting white blood cells, cannot directly reach the valves through the bloodstream. If bacteria begins to grow on the valves, it is difficult to fight the infection, whether through the body’s own immune system or through medications that rely on the blood system for delivery.
http://www.heart.org/HEARTORG/Conditions/More/HeartValveProblemsandDisease/Heart-Valves-and-Infective-Endocarditis_UCM_450448_Article.jsp#.WDPzd9J96M8
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