Endocarditis is infection and inflammation of the lining of a valve in the heart. "Culture-negative endocarditis " is a type of endocarditis in which no causative organisms can be grown in a culture taken from the bloodstream. This sometimes occurs when blood cultures are drawn after treatment (antibiotics) has already been initiated, or if the culprit organism is a fastidious organism that is difficult to grow in readily available culture media.
Alternative Names
Endocarditis (culture-negative)
Causes, incidence, and risk factors
Endocarditis is most likely to occur in people whose cardiac valves have certain predisposing factors for infection; for example, the valves may have been scarred in childhood by rheumatic fever, or are congenitally different from normal (bicuspid aortic valve, mitral valve prolapse). Persons with prosthetic valves (i.e., valves which have been surgically replaced) are also more prone to having bacteria land on them and grow prosthetic "vegetations". Other patients at increased risk for endocarditis are those with previous endocarditis or congenital heart diseases. Intravenous drug users are also at especially high risk of acquiring culture-negative endocarditis from contaminated syringes. In patients with endocarditis there is usually an obvious source of infection, such as an infected intravascular catheter, a dental abscess, or an infected skin lesion but in many patients there is no history of infection. An estimated 10,000 to 15,000 new cases of endocarditis are diagnosed yearly in the United States.
Signs and tests
Signs of endocarditis include:
tachycardia (fast heart rate) fever a new heart murmur on cardiac exam The following tests may be requested:
an ECG and a chest X-ray. a complete blood count. blood cultures: these are often used to identify the germ causing the infection, but when certain bacteria called "fastidious organisms" (such as Bartonella, Coxiella, Mycobacterium, and germs of the HACEK group) are responsible for the endocarditis, cultures may not grow germs. The identification of responsible germs in such cases must be done through the use of special culture conditions and prolonged incubation time. Often, the diagnosis can only be made based on serological or DNA studies. an echocardiogram is used to picture the valves of the heart, to visualize any vegetations (abnormal structures prodcued by the germs in the heart), and to evaluate heart function. the most clear images of a patient's valves are often obtained with a transesophageal echocardiogram (TEE), a special echocardiogram done by introducing a small probe passed into the patient's mouth down the esophagus.
Treatment
Endocarditis is treated with intravenous antibiotics or antifungal medications for a prolonged time. Some patients may require heart surgery.
Complications
Complications of endocarditis include congestive heart failure, perivalvular abscesses, intracardiac fistulae (i.e., abnormal connections within the heart), and emboli (blood clots which can travel through the circulation and cause strokes or other problems related to obstructed blood vessels). All these complications usually require surgery, either to remove vegetations or abscesses, to repair the valves or to replace them with prostheses.
Prevention
Patients with mitral valve prolapse, valve prostheses, previous endocarditis, congenital heart diseases, and intravenous use of illegal drugs are are at increased risk for endocarditis. Patients at known increased risk for endocarditis should consult their primary physician about the need to receive antibiotics prior to dental or genitourinary procedures. Intravenous drug users should seek treatment for addiction or if that is not possible, use new (i.e., sterile) syringes and clean the injection site before every injection to avoid blood infections leading to endocarditis. For all patients at risk for endocarditis, maintenance of meticulous dental hygiene is of equal importance to antibiotic prophylaxis in the prevention of endocarditis.