Culture-negative endocarditis is an infection and inflammation of the lining of one or more heart valves in which no endocarditis-causing germs can be identified on a blood culture
. The reason for this is that certain germs just do not grow well in the laboratory setting, or because some patients have previously received antibiotics that keep such germs from growing.
Causes, incidence, and risk factors
Endocarditis is usually a result of a blood infection. Bacteria can enter the bloodstream during certain medical procedures, including dental procedures, and travel to the heart, where it can settle on damaged heart valves.
Existing heart disease and problems with your heart valves make you more likely to develop endocarditis. Risk factors include:
- Artificial heart valves
- Congenital heart disease (atrial septal defect, patent ductus arteriosus, and others)
- Heart valve problems (such as mitral insufficiency)
- History of rheumatic heart disease or previous endocarditis
Intravenous drug users are also at risk for this condition, because dirty needles can cause bacteria to enter the bloodstream.
However, an organism commonly found in the mouth, Streptococcus viridans, can cause endocarditis. This is why dental procedures increase your chances for developing this condition. Such procedures are especially risky for children with congenital heart conditions. As a result, it is common practice for children with some forms of congenital heart disease and adults with certain heart valve conditions to take antibiotics before any dental work.
An estimated 10,000 to 15,000 new cases of endocarditis are diagnosed each year in the United States.
Symptoms of endocarditis may develop slowly (subacute) or suddenly (acute). Fever is the classic symptom and may persist for days before any other symptoms appear.
Other symptoms may include extreme fatigue and breathing difficulty.
Signs and tests
There is usually an obvious source of infection, such as an infected catheter, a dental abscess, or an infected skin lesion. However, in many patients there is no history of infection.
A physical exam may reveal:
The following tests may be done:
- Chest x-ray
- Complete blood count
- Echocardiogram (ultrasound of the heart)
- Transesophageal echocardiogram (TEE), a special echocardiogram done by introducing a small probe into the patient's mouth and down the esophagus
You will be admitted to the hospital so you can receive medicines through a vein. Long-term, high-dose antibiotic or antifungal treatment is needed. Treatment is usually given for 4 - 6 weeks.
Surgery may be needed to replace damaged heart valves.
Heart valves may be damaged if diagnosis and treatment are delayed.
Abnormal connections within the heart
Blood clots that travel to brain, kidneys, lungs, or abdomen
Congestive heart failure
Rapid or irregular heartbeats, including atrial fibrillation
Severe valve damage
The American Heart Association recommends preventive antibiotics for people at risk for infectious endocarditis before:
- Certain dental procedures
- Surgeries on respiratory tract or infected skin, skin structures, or musculoskeletal tissue
Antibiotics are more likely to be recommended those with the following risk factors:
- Artificial heart valves
- Certain congenital heart defects, both before or possibly after repair
- History of infective endocarditis
- Valve problems after a heart transplant
Continued medical follow-up is recommended for people with a previous history of infectious endocarditis.
Persons who use intravenous drugs should seek treatment for addiction. If this is not possible, use a new needle for each injection, avoid sharing any injection-related paraphernalia, and use alcohol pads before injecting to reduce risk.
Fowler VG Jr, Scheld WM, Bayer AS. Endocarditis and Intravascular Infections. In: Mandell GL, Bennett JE, Dolin R, eds. Principles and Practice of Infectious Diseases. 7th ed. Philadelphia, Pa: Elsevier Churchill Livingstone; 2009; chapt 77.
Karchmer AW. Infective Endocarditis. In: Libby P, Bonow RO, Mann DL, Zipes DP, eds. Braunwald's Heart Disease: A Textbook of Cardiovascular Medicine. 8th ed. St. Louis, Mo: WB Saunders; 2007:chap 63.
Wilson W, Taubert KA, Gewitz M, et al. Prevention of infective endocarditis: guidelines from the American Heart Association: a guideline from the American Heart Association Rheumatic Fever, Endocarditis, and Kawasaki Disease Committee, Council on Cardiovascular Disease in the Young, and the Council on Clinical Cardiology, Council on Cardiovascular Surgery and Anesthesia, and the Quality of Care and Outcomes Research Interdisciplinary Working Group. Circulation. 2007 Oct 9;116(15):1736-54.
Daniel Levy, MD, Infectious Disease, Maryland Family Care, Lutherville, MD. Review provided by VeriMed Healthcare Network. Also reviewed by David Zieve, MD, MHA, Medical Director, A.D.A.M., Inc.