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Most patients with infective endocarditis (IE) have an identifiable predisposing cardiac abnormality or risk factor for disease. More than one half of all cases in the U.S. and Europe occur in patients >60 years old.1,2 This trend is due to an increase in the incidence of degenerative valve disease requiring valve replacement and the increasing use of invasive medical procedures and devices, such as hemodialysis, IV catheters, and intracardiac devices. For a discussion of endocarditis in children, refer to Chapter 122B, Pediatric Heart Disease: Acquired Heart Disease.

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Clinical presentation of IE is nonspecific and variable, as the disease can affect nearly every organ system and have either an indolent or fulminant course. Diagnosis relies on a set of explicit criteria, which include findings from blood culture, echocardiography, and several days of inpatient observation. Unrecognized disease is associated with a wide range of complications and mortality approaching 100%.

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In developed countries, the incidence of IE ranges from 2.06 to 11.6 cases per 100,000 patient years.1,3–5 Incidence is higher in urban versus rural populations, likely reflecting the impact of injection drug use. The disease is uncommon among children, where it is associated primarily with structural congenital heart disease, rheumatic heart disease, or nosocomial, catheter-related bacteremia. IE affects men more commonly than women, with male-to-female ratios ranging from 3:2 to 9:1.1

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The mitral valve is most commonly affected, followed in decreasing frequency by the aortic, tricuspid, and pulmonic valves. Significant variation in mortality occurs based on organism, presence of complications, and treatment modality (medical versus surgical).

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Most cases occur either in those with a predisposing identifiable cardiac structural abnormality (congenital or acquired) or a recognized risk factor for disease (including injection drug use, indwelling catheters, poor dental hygiene, or infection with human immunodeficiency virus).

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For native valve related endocarditis in the developed world, mitral valve prolapse is a common predisposing cardiac lesion. Other underlying structural defects include congenital defects (most commonly bicuspid aortic valve), degenerative cardiac lesions (particularly calcific aortic stenosis), and rheumatic heart disease. In developing countries, rheumatic heart disease remains the leading underlying risk factor. For native valve–related endocarditis, left-sided disease predominates, and mortality ranges from 16% to 27%. Risk factors associated with mortality for patients with left-sided native valve endocarditis include comorbidity, abnormal mental status, congestive heart failure (CHF), bacterial etiology other than Streptococcus viridans and Staphylococcus aureus, and medical therapy without valve surgery.6

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Although the exact incidence is difficult to determine, estimated risk for endocarditis in injection drug users is 2% to 5% per year. Mean age of disease is 30 years old. When endocarditis occurs in injection drug users, it has a predilection for the tricuspid valve. Other features of injection drug use–related IE include increased susceptibility to recurrence (approximately 40%) and increased mortality (56%) in those with concurrent human immunodeficiency virus and evidence of immunosuppression (as measured by ...

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