Which cardiac lesion poses the highest risk for infective endocarditis?

Prosthetic cardiac valves and a history of previous bacterial endocarditis represent a significant risk factor for developing infective endocarditis. This increased risk is because prosthetic valves can provide a surface for bacterial colonization, and patients with a history of previous endocarditis have predisposing factors that might have initially led to their condition.

The risk of infection is heightened due to the presence of foreign material (the prosthetic valve), which can disrupt normal blood flow and provide an environment conducive to bacterial growth. Additionally, the prior episode of endocarditis implies that the patient may have underlying vulnerabilities such as pre-existing valve abnormalities or immune response issues that can facilitate the recurrence of infection.

Infective endocarditis occurs when bacteria enter the bloodstream and attach to damaged areas of the heart or prosthetic material. Overall, the presence of prosthetic valves significantly elevates the risk because of the unique circumstances surrounding these devices, making patients highly susceptible to infections that can lead to serious cardiovascular complications.