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CME Cardiology Clinical Medicine 2010, Vol 10, No 2: 188–91 Infective endocarditis tion, abscesses, fistulae and leaflet perfo- ration are all more reliably detected using this technique.7 Wazir Baig, consultant cardiologist; (now 17% of cases). Enterococci are the Jonathan Sandoe, consultant third most frequent cause of IE and con- Blood culture-negative microbiologist sistently account for approximately 10% endocarditis Departments of Cardiology and of episodes.3 Further classification by type of car- Depending on the patient group and type Microbiology, Leeds General Infirmary, diac structure divides IE into: of structure affected, 5–12% of IE cases Leeds are blood culture-negative. Negative cul- Infective endocarditis (IE) is a non-con- • native valve endocarditis tures are more frequent in prosthetic tagious infection of intracardiac struc- • prosthetic valve endocarditis, and valve and cardiac device-related IE.3 tures which usually affects the valves of • cardiac device-related IE – most Contributing factors include the recent commonly affecting permanent use of antibiotics, organisms that are dif- the heart but, in contemporary practice, pacemakers and implantable car- ficult to culture and inadequate blood may also involve infection of indwelling dioverter-defibrillators. sampling. A novel technique in these cardiac devices. Patients occasionally cases is broad-range 16S ribosomal RNA present acutely with severe sepsis but gene polymerase chain reaction analysis most still manifest with a non-specific Diagnostic methods of tissue taken at the time of valve surgery illness of insidious onset having been (where appropriate). The results can symptomatic for several weeks or The essential diagnostic methods for IE are blood cultures and echocardiog- guide the appropriate choice of antimi- months. IE remains a challenging disease crobial therapy. The technique is cur- because of its variable presentation and raphy. These investigations are needed to confirm continuing bacteraemia and to rently limited to patients undergoing frequent difficulty in securing the diag- valve surgery, but application to whole nosis. Population-based studies are demonstrate vegetations and/or new par- avalvular regurgitation of prosthetic blood samples should soon be feasible.8 scarce, but US data indicate the incidence Consideration should also be given to is currently 5–7/100,000 person years,1 valve(s). The synthesis of clinical and microbiological findings with echocar- serological testing for Bartonella, Brucella, but slowly rising2 as a result of: Q-Fever, Mycoplasma and Legionella diographic appearances is now known as species when blood cultures are negative. • an ageing population who develop the Duke criteria, first published in 1994. degenerative valve lesions The original algorithm has been modi- • the increasing number of patients fied and provides an objective frame- Antimicrobial regimens who receive prosthetic heart valves work to assist diagnosis (Table 1).4,5 and other implantable cardiac devices Definitions of positive echocardio- Knowledge of the causative organism in IE • the rising number of patients who graphic findings in IE are provided in is key to the selection of appropriate receive renal replacement therapy via Table 2. antimicrobial therapy. Whether infection long-
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