Infective endocarditis: Clinical

Infective endocarditis is an infection of the endocardium, the inner layer of the heart.

Most cases are due to a bacterial or fungal infection of the endocardial lining the heart valves.

But in order to reach the heart valves, a microbe has to first get into the bloodstream.

There are a few ways that might happen - microbes can hop into a blood vessel near an open wound or an abscess, or during a dental or surgical procedure, or they can go directly in when a person gets injected with an infected needle which sometimes happens while using illicit drugs.

Microbes generally like to latch onto heart valves that are already damaged, because it makes it easier for them to adhere and form vegetations.

Risk factors for infective endocarditis include cardiac factors, like prior infective endocarditis, a prosthetic valve or implantable cardiac device like a pacemaker, or valvular or congenital heart disease; and noncardiac factors like intravenous drug use, having an intravenous catheter, immunosuppression, or a recent dental or surgical procedure.

Clinically, infective endocarditis is categorized as either native valve endocarditis when it affects a previously normal heart valve, or prosthetic valve endocarditis when it affects an artificial heart valve.

Native valve endocarditis is mainly caused by Staphylococcus aureus, viridans Streptococci, and is often seen in intravenous drug users, since these bacteria are normally present in the skin.

Prosthetic valve endocarditis is mostly caused by Staphylococcus aureus as well - specifically methicillin resistant Staphylococcus Aureus or MRSA, since it’s frequently nosocomial.