endocarditis (ĕnˌdōkärdĪˈtĭs) [key], bacterial or fungal infection of the endocardium (inner lining of the heart) that can be either acute or subacute. In the acute form the symptoms (fever, malaise, fatigue, weight loss, anemia) are directly related to the presence of an active infection that runs its course within a few weeks. Acute endocarditis may follow respiratory infection, surgery, or other trauma; but in some cases the source of infection is unknown. A major cause of endocarditis is the use of contaminated intravenous needles by drug addicts. Bacterial endocarditis is an insidious, often progressive, disease that can lead to kidney failure and congestive heart failure. The causative agent in many cases of subacute disease is Streptococcus viridans. Endocarditis is often a complication of Lyme disease. A previously damaged valve increases the risk of infection tenfold. The most common diseases causing these predisposing valvular deformities are rheumatic fever and congenital heart disease. Thrombi associated with the infection on the valve often dislodge and spread septic emboli throughout the body that may damage the kidney. Primary diagnostic symptoms are fever and a changing heart murmur. Physical diagnosis can be confirmed by the use of echocardiography (ultrasound). Treatment with high doses of antibiotics often kills the bacteria, but the damage to the valve may put an additional strain on the heart that can eventually lead to cardiac failure. However, it is sometimes possible through follow-up corrective surgery to repair or replace valves damaged by endocarditis.