What are the symptoms of bacterial endocarditis?

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Endocarditis is an infection of the tissue lining the heart. Almost always, the disease involves the heart valves. Bacteria, fungi and in rare cases even parasites can cause endocarditis, but bacteria are the most common culprits. There are two main categories of bacterial endocarditis: subacute (gradual onset) and acute (sudden onset).

In subacute endocarditis, the causes are usually bacteria species of the group called Streptococcus. These bacteria are not the ones that cause strep throat, but they are organisms that commonly live in the mouth. The bacteria enter the bloodstream from the mouth. Sometimes this occurs when there is a minor dental infection, but in most cases, there is no evidence of such an infection. Once in the bloodstream, the bacteria adhere to the heart valves and cause the formation of growths known as "vegetations." The bacteria are present deep in these vegetations, eluding the person's infection-fighting immune system.

Fever is the most common symptom, but because the course of disease is gradual, a patient may be ill for weeks or even months before seeing a physician. The patient, being ill for so long, loses weight and becomes anemic. The vegetations may be quite large before diagnosis. Pieces may break off, causing strokes and physical signs such as lesions on the fingers and palms, changes in the retina of the eye and tiny red marks on the skin called petechiae. Other infections may develop throughout the body. Heart failure may occur, but this generally happens late in the illness. Without antibiotic therapy, essentially all victims of this infection die.

In acute bacterial endocarditis, the most common cause is Staphylococcus aureus, or "staph." The bacterium enters the bloodstream from the skin. This can occur in people who inject illicit drugs, use an intravenous catheter or have a boil (skin abscess). In some patients, the source of a staph bloodstream infection is unknown. With staph endocarditis, the patient becomes ill quite quickly, usually seeking medical help within a few days of the first symptoms. Fever is the most prominent symptom, affecting the vast majority of patients. The bacterium can rapidly destroy an infected heart valve, resulting in heart murmurs and eventually heart failure. The mortality rate even with antibiotic therapy is more than 30 percent in most studies and may be as high as 70 percent among certain high-risk populations.

The diagnosis of endocarditis can be simple if all of the signs and symptoms are present. Blood samples cultured in a laboratory to grow any organism present will usually reveal the source of the infection, and the result will help the physician choose which antibiotics to use. An echocardiogram (an ultrasound exam of the heart) will usually show the vegetations. Treating endocarditis requires several weeks of intravenous antibiotics. Surgery may be required if the valves are severely damaged, if an abscess develops in the heart or if antibiotics do not cure the infection.