Why are valves preferentially affected in endocarditis?

[Polycherry]

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?

---

Members don't see this ad.

 

[Instatewaiter]

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.

Are there theories for this?

It is actually the turbulence you need. This turbulence causes endothelium damage which predisposes you to endocarditis. Furthermore, the valves really do not have an active immunologic response so the combination of turbulence + little immunologic response = more likely to have endocarditis.

 

[Mad Jack]

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2440405/

It has to do with the structure and histology would be my guess. The valves are structurally different in many ways from the rest of the heart, and thus will be affected differently. They also have less perfusion, which likely impacts their ability to stave off microbes. Couple this with the turbulance that is constantly impacting them, and you've got a recipe for vegetations.

 

[Polycherry]

It is actually the turbulence you need. This turbulence causes endothelium damage which predisposes you to endocarditis. Furthermore, the valves really do not have an active immunologic response so the combination of turbulence + little immunologic response = more likely to have endocarditis.

How does it matter if they are less perfused? Cant the antibodies act from the blood that is all around? After all it the hearts filled witgh blood, right?

 

[Mad Jack]

How does it matter if they are less perfused? Cant the antibodies act from the blood that is all around? After all it the hearts filled witgh blood, right?

It's not just antibodies- neutrophils, lymphocytes, and macrophages require time to reach a location in which they can combat infection. With the constant movement of blood around the valves due to turbulence, chemotaxis is likely difficult, as the chemotactic messenger signals are being tossed about by flow currents and then completely ejected from the chamber with each heartbeat. That's just a theory based on mechanics though, you'd probably have to discuss it with a good pathophysiology professor for a better answer, unless we've got someone kicking around here that is a master of path minutia that are beyond the level of the Steps.