CLINCAL SUBJECTSOXFORD STUDY SERIES

Emergency Management of Infectious Diseases Second Edition 2018

Emergency Management of Infectious Diseases Second Edition 2018

Emergency Management of Infectious Diseases Second Edition 2018

Emergency Management of Infectious Diseases Second Edition 2018 Infectious endocarditis (IE) is a diffi cult diagnosis to make  in the emergency setting. Early diagnosis and management  requires an understanding of endocarditis risk factors, typical  and atypical clinical presentations, and current diagnostic and
empiric treatment strategies.

n developed countries, the incidence of IE is roughly 5 cases per 100,000 persons per year. It more commonly aff ects males (2:1). Well- recognized risk factors for IE include presence of a prosthetic heart valve (which carry an annual incidence of approximately 1%), congenital heart disease, endocardiac  devices, injection drug use (see Chapter 61 ), and a prior history  of endocarditis. Rheumatic heart disease is now an uncommon
predisposing risk factor in the United States. However, in  modern series, there is no easily identifi able risk factor for
underlying valve damage in approximately 50% of endocarditis
cases. Such cases are believed to be due to age- related degenerative valve disease and subtle immunosuppresion from diabetic endocarditis and other factors. Health- care associated cases, oft en in the elderly, account for a growing proportion of endocarditis in the United States.

Infective endocarditis occurs when circulating pathogens adhere to damaged endothelium and form a vegetation, usually on or around a cardiac valve. Abnormal turbulent fl ow and damaged endothelium lead to fi brin and platelete deposition  which presents a nidus for bacterial infection during bacteremia. In the setting of frequent bacteremia, such as intravenous drug use and dental infection, IE may occur even without an  identifi able pathologic valvular lesion. Growth of the infected  vegetation eventually leads to valve destruction and impaired
function, typically regurgitation, and eventually heart failure.
Invasion of the myocardium can lead to paravalvular abscess
and heart block. Large, mobile vegetations are associated with
embolization and metastatic infection (see below).

Th e list of pathogens that have been reported to cause IE is enormous and includes fungi and protozoa. Th e most
common etiolgies, however, are gram- positive cocci, including  Staphylococcus species, both S.  aureus and coagulase negative Staphylococcus , and Streptococcal species, particularly
viridans Streptococci and group D Streptococcus . S.  aureus  is both the most common etiology and the pathogen most  oft en associated with metastatic complications. Enterococcus  is common in the elderly. Th e clinical setting may suggest the  pathogen involved:  S. aureus is the most common in injection  drug users, viridans Streptococci in patients with recent dental procedures, and gram- negative bacilli in patients that have
undergone invasive genitourinary procedures.

Pathogens that are less commonly implicated in IE include  the “HACEK” ( Haemophilus aphrophilus , Haemophilus  paraphrophilus , Haemophilus parainfl uenzae , Actinobacillus
actinomycetemcomitans , Cardiobacterium hominis , Eikenella
corrodens , and Kingella kingae ) group of fastidious bacteria,  Bartonella , chlamydia, Legionella , and fungi. Infections with  these organisms may be diffi cult to detect because they do not
always grow in routine blood cultures.

 

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