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  1. Which cardiac lesions predispose to bacterial endocarditis?

  2. If antibiotic prophylaxis is to be administered, when should the antibiotic be given?

  3. What are the most common symptoms in subacute bacterial endocarditis?

  4. When bacterial endocarditis is suspected, what are the skin lesions that should be searched for, and how often are they seen?

  5. How should blood samples for culture be drawn if the clinician suspects bacterial endocarditis?

  6. In the patient with Staphylococcus aureus line-related bacteremia, how long should antibiotics be administered?

  7. Which key physical finding is most helpful for detecting cardiac tamponade?



Acute endocarditis is life-threatening and often requires surgical intervention. Subacute endocarditis is an indolent disease that can continue for months.


The incidence of infective endocarditis in the United States increased from 9.3 to 15 per 100,000 from 1998 to 2011. The rapid treatment of group A streptococcal infections in the United States and other developed countries has reduced the case of rheumatic heart disease, a major risk factor for endocarditis. However, in developing countries where resources are limited rheumatic heart disease remains prevalent. One of the leading conditions that predisposes to endocarditis in developed countries is calcific valve disease. This is a disease of the elderly and as life expectancy increases the incidence of calcified heart valves is increasing. The increased use of central intravenous catheters, implantable cardiac devices, and prosthetic cardiac valves as well as the intravenous opioid abuse epidemic also help to explain the rising incidence of endocarditis in developed countries. Males are more likely than females to develop infective endocarditis.

KEY POINTS About the Epidemiology of Infective Endocarditis

  1. Increasing in incidence, now 15/100,000 in the United States up from 9.3/100,000.

  2. The rise in incidence is explained by:

    1. the increasing elderly population with predisposing calcific valve disease,

    2. increased use of central venous catheters, implantable cardiac devices, and prosthetic valves, and

    3. the IV opioid epidemic.

Pathogenesis and Predisposing Risk Factors

Host Factors

Infective endocarditis is usually preceded by the formation of a predisposing cardiac lesion. Preexisting endocardial damage leads to the accumulation of platelets and fibrin, producing nonbacterial thrombotic endocarditis (NBTE). This sterile lesion serves as an ideal site to trap bacteria as they pass through the bloodstream. Cardiac lesions that result in endocardial damage and predispose to the formation of NBTE include rheumatic heart disease, congenital heart disease (bicuspid aortic valve, ventricular septal defect, coarctation of the aorta, and tetralogy of Fallot), mitral valve prolapse, degenerative heart disease (calcific aortic valve disease), and prosthetic valve placement.

Risk factors of endocarditis reflect the pathogenesis of the disease. Patients with congenital heart disease and rheumatic heart disease, those with an audible murmur associated with mitral valve prolapse, and elderly patients with calcific aortic stenosis are all at ...

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