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Acute endocarditis is a febrile illness that rapidly damages cardiac structures, seeds extracardiac sites hematogenously, and can progress to death within weeks. Subacute endocarditis follows an indolent course, rarely causes metastatic infection, and progresses gradually unless complicated by a major embolic event or a ruptured mycotic aneurysm.

  • Epidemiology: In developed countries, the incidence of endocarditis ranges from 4 to 7 cases per 100,000 population per year, with higher rates among the elderly.

    • – Predisposing conditions include association with health care, congenital heart disease, illicit IV drug use, degenerative valve disease, and the presence of intracardiac devices.

    • – Chronic rheumatic heart disease is a risk factor in low-income countries.

    • – Of endocarditis cases, 16–30% involve prosthetic valves, with the greatest risk during the first 6–12 months after valve replacement.

  • Etiology and microbiology: Because of their different portals of entry, the causative microorganisms vary among clinical types of endocarditis.

    • – In native-valve endocarditis (NVE), viridans streptococci, staphylococci, and HACEK organisms (Haemophilus spp., Aggregatibacter spp., Cardiobacterium spp., Eikenella corrodens, and Kingella kingae) enter the bloodstream from oral, skin, and upper respiratory tract portals. Streptococcus gallolyticus subspecies gallolyticus (formerly S. bovis biotype 1) originates from the gut and is associated with polyps or colon cancer.

    • – Health care–associated NVE, frequently due to Staphylococcus aureus, coagulase-negative staphylococci (CoNS), and enterococci, may have a nosocomial onset (55%) or a community onset (45%) in pts who have had extensive contact with the health care system in the preceding 90 days.

    • – Prosthetic-valve endocarditis (PVE) developing within 2 months of surgery is due to intraoperative contamination or a bacteremic postoperative complication and is typically caused by CoNS, S. aureus, facultative gram-negative bacilli, diphtheroids, or fungi. Cases beginning >1 year after valve surgery are caused by the same organisms that cause community-acquired NVE. PVE due to CoNS that presents 2–12 months after surgery often represents delayed-onset nosocomial infection.

    • – Cardiovascular implantable electronic device (CIED)–related endocarditis involves the device itself or the endothelium at points of device contact, with occasional concurrent aortic or mitral valve infection. One-third of cases of CIED endocarditis present within 3 months after device implantation or manipulation, one-third present at 4–12 months, and one-third present at >1 year. S. aureus and CoNS (often methicillin-resistant strains) cause the majority of cases.

    • – Endocarditis occurring among IV drug users, especially that involving the tricuspid valve, is commonly caused by S. aureus (often a methicillin-resistant strain). Left-sided valve infections among IV drug users are caused by Pseudomonas aeruginosa and Candida, Bacillus, Lactobacillus, and Corynebacterium spp. in addition to the usual causes of endocarditis.

    • – About 5–15% of endocarditis cases are culture negative, and one-third to one-half of these cases are due to prior antibiotic exposure. The remainder of culture-negative cases represent infection by fastidious organisms, such as the nutritionally variant bacteria Granulicatella and Abiotrophia spp., HACEK organisms, Coxiella burnetii, Bartonella spp., Brucella spp., and Tropheryma whipplei.


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