Last updated: November 6, 2014
Synonyms: Infective endocarditis, subacute bacterial endocarditis (SBE).
ICD-9 Code: Infective endocarditis, 421.0; prosthetic valve endocarditis,996.61.
ICD-10 Code: I33
Definition: Infective endocarditis implies infection of valvular or mural endocardium. Endocarditis is an uncommon cause of fever, arthralgia, and low back pain.
Etiology: Most infections occur over abnormal valves or damaged endocardial surfaces, where abnormal blood flow patterns lead to development of platelet-thrombin clots that serve as foci for infections. Some cases occur in intravenous drug abusers and are caused by more highly virulent staphylococcal and streptococcal organisms. Subacute endocarditis may be caused by 13- hemolytic streptococci, Streptococcus bovis, and enterococci. Endocarditis with intravenous drug abuse may be caused by S. aureus, Pseudomonas spp, gramnegative species, and Candida spp.
Pathology: Infections are usually formed over areas of sterile vegetations consisting of platelets and fibrin. Most occur in high-pressure areas, usually on the left side of the heart. Underlying valves may show thickening from previous damage.
Demographics: Those at risk include older individuals; those with rheumatic valvular disease or prosthetic valves; intravenous drug abusers; those with indwelling catheters; and those with bacteremia.
Cardinal Findings: Most patients have fever (with or without night sweats) and a cardiac murmur. Tender nodules on the fingertips (Osler ’s nodes) and splinter hemorrhages under the fingernails may be seen. Anorexia, weight loss, arthralgias, frank arthritis, low back pain, and splenomegaly are common. Back pain may be caused by bacteremia or septic emboli resulting in septic discitis. A small number of patients develop septic arthritis owing to seeding with the causative organism. Multiple joints may be involved.
Complications: Congestive heart failure, ruptured valve cusp or chordae tendineae, abscesses (myocardial, aortic root, brain), or infarction (lung, spleen, bowel, or myocardium) from emboli may be seen. Renal failure from glomerulonephritis has been described.
Diagnostic Tests: Positive blood cultures are diagnostic, but a significant minority of patients remain culture negative. Previous treatment with antibiotics may alter culture results. Elevated levels of acute-phase reactants (ESR, CRP) are expected. In subacute endocarditis, an anemia of chronic disease, low complement levels, and positive RF may be seen.
Imaging: Echocardiography, including transesophageal approaches, is recommended.
Differential Diagnosis: Patients may present with fever of unknown origin. Splinter hemorrhages and Osler nodes may suggest a systemic vasculitis (e.g., Churg-Strauss, cryoglobulinemia). Multiple swollen joints and inflamed joints might suggest gout or reactive arthritis. Some patients are transiently positive for RF, so polyarthritis might be mistaken for RA. Other possibilities include osteomyelitis, rheumatic fever, and tuberculosis.
Therapy: Definitive therapy requires an extended course of appropriate antibiotics. Subsequent antibiotic prophylaxis is recommended for all invasive procedures.
Surgery: Heart valve replacement may be required.
Prognosis: Long-term outcome is dictated by the severity of the underlying heart disease or drug addiction or development of complications.
Roberts-Thomson PJ, Rischmueller M, Kwiatek RA, et al. Rheumatic manifestations of infective endocarditis. Rheumatol Int 1992;12:61–63. PMID:1411084