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Infective endocarditis (IE) is uncommon. The yearly incidence reported in developed countries ranges between 1.8 and 6.2 per 100 000 of the population [1–5]. However, these estimates may be imprecise for a variety of reasons. Although it affects neonates [6,7], infants [8], children [9,10], young adults, and pregnant women [11], the incidence increases after 30 years of age and exceeds 10 per 100 000 for people aged over 50 years [12]. It is a life-threatening diseasewith a substantial in-hospital morbidity and mortality (approximately 20%) despite improved techniques to aid diagnosis and modern antibiotics and surgical therapies [13]. One-year mortality approaches 40% [14]. Prosthetic valve endocarditis (PVE), although uncommon (0.1–2.3% per patient year) carries an even higher mortality rate [15–17] and prevention of IE is therefore extremely important [18].

The clinical manifestations of IE will depend on factors such as the nature of any predisposing condition, the virulence of the responsible organism, and the portal of entry [1].

Mild to moderate anemia is commonly present in IE with a normochromic, normocytic picture. Neutrophil leukocytosis is common and the erythrocyte sedimentation rate (ESR) and C-reactive protein (CRP) are elevated in 90% of patients and the latter have been proposed as additional minor criteria to the Duke classification of IE [1–4]. Intraleukocyte bacteria can be seen in buffy coat preparations of blood in up to 50% of cases [5].

Criteria for the diagnosis of IE were proposed by von Reyn and colleagues in 1981 based on analysis of symptoms, clinical signs, and blood cultures [1]. These were subsequently refined by Durack and colleagues at the Duke Endocarditis Service in 1994, taking into account information obtained by echocardiography and introducing the concept of major and minor diagnostic criteria [2] (Table 4.1). The advantages and limitations of the Duke criteria for the diagnosis of IE have been studied and modified but echocardiographic data, serology, and culture of excised tissue appear to improve the specificity and sensitivity of the diagnostic criteria [3–17]. Comparison has also been made between the Duke and other criteria (Beth Israel) for the diagnosis of IE and although the modified Duke criteria appear to be superior, confirmatory studies are few and small [18,19]. Larger studies are needed.

Despite medical treatment, IE continues to cause significant morbidity and mortality (20%). Prevention therefore is a priority as is early diagnosis and adequate management based on appropriate antibiotic therapy and in many cases cardiac surgery. Antimicrobial prophylaxis before selected procedures in patients at risk has become routine in most countries, despite the fact that no prospective study has been performed that proves that such therapy is definitely beneficial [1–3]. Animal experiments and some human studies have, however, suggested benefit from prophylactic antibiotics [4]. Even if prophylaxis is effective, it can only prevent a minority of cases of endocarditis and it is not cost-effective as a general strategy. Nevertheless, current “best practice” continues to favor the use of antibiotic prophylaxis of selected patients at risk of IE who are undergoing procedures that can cause bacteremia.Guidelines and advice have been published by expert groups in both Europe and the USA and the differences in recommendations are minor [5–10]. However, the guidelines represent consensus recommendations based mainly on data from animal models, case-control studies and case series.

An algorithm for the management of patients with infective endocarditis is shown in Figure 6.1.

General principles and specific guidelines for medical treatment have been published in the UK, Europe, and the USA [1–8].

Infective endocarditis requires prompt treatmentwith appropriate antimicrobial drugs, administered parenterally in doses sufficient to eradicate the organism from the blood, from vegetations and from local or metastatic foci of infection. Parenteral administration ensures complete bioavailability, high serum concentrations, and good penetration into the vegetation. Treatment should begin immediately after blood cultures have been taken—especially in patients with severe sepsis, severe valvular dysfunction, conduction disturbance or embolic events, and should be adjusted once the organism has been identified and the antibiotic sensitivities are known.

In many patients with IE, the infection can be cured with medical treatment alone [1]. However, in 25–30% medical treatment alone is insufficient and must be combined with surgery. The purpose of surgery is to control infection by debridement and removal of necrotic tissue and to restore cardiac morphology by surgical repair and/or valve replacement. The indications and optimal timing for surgery in infective endocarditis have been recently discussed in the literature [2].

The determinants of early and late survival in patients with IE have been identified [1]. Several factorsworsen the prognosis of IE and early surgical intervention may be necessary [2].

Clinical factors include old age, the presence of heart failure, renal failure, neurological symptoms, systemic emboli, and delay in diagnosis. Persistent fever beyond the first week of treatment often indicates the development of complications such as progressive valve destruction, extension of infection to the valve's annulus, development of perivalvular abscess, or the presence of septic emboli.