Subacute bacterial endocarditis (also called endocarditis lenta) is a type of endocarditis (more specifically, infective endocarditis).
It can be confused with essential mixed cryoglobulinemia.
It can be considered a form of Type III hypersensitivity.
Osler's nodes can indicate this condition. Nail clubbing is also often seen in subacute endocarditis.
It is usually caused by a form of streptococci viridans bacteria that normally live in the mouth and throat (Streptococcus mutans, mitis, sanguis or milleri). Other strains of streptococci (bovis and equines) can also cause subacute endocarditis, usually in patients who have a form of gastrointestinal cancer.
Underlying structural valve disease is usually present in patients before developing subacute endocarditis. It is less likely to lead to septic emboli than is acute endocarditis, but subacute endocarditis has a relatively slow process of infection and, if left untreated, can worsen for up to one year before it is fatal.
In cases of subacute bacterial endocarditis, the causative organism (streptococcus viridans) needs a previous heart valve disease to colonize and cause such disease.
On the other hand, in cases of acute bacterial endocarditis, the organism can colonize on the healthy heart valve, causing the disease.
The standard treatment is with a minimum of four weeks of high-dose intravenous penicillin with an aminoglycoside such as gentamicin. The use of high-dose antibiotics is largely based upon animal models. Leo Loewe of Brooklyn Jewish Hospital was the first to successfully treat subacute bacterial endocarditis with penicillin. Loewe reported seven cases in 1944.