DIFFERENTIAL DIAGNOSIS
History
SBE is a very indolent infection. Its most common symptoms are low-grade fever, fatigue,
anorexia, backache (presenting symptom in 15% of cases), and weight loss. Much less
frequently, it may present as a stroke or congestive heart failure. Both of these events arise
from embolic/and/or immunological processes. They usually occur well into the disease
process when diagnosis and therapy has been delayed for several months. Less than 50% of
patients have had previously recognized valvular disease. The usual interval between
initiating bacteremia and symptoms of subacute disease is two weeks, rarely as long
as four (3,123).
The clinical course of acute IV is much more aggressive. It is marked by acute onset of
high-grade fever with rapidly progressive valvular destruction often associated with
burrowing ring abscesses. These insults to the infected valves can lead to intractable heart
failure and sometimes to complete heart block well within a week. The patient should always
be questioned about intravenous drug abuse or any recent staphylococcal infections or
invasive procedures of any type.
Physical Examination
Fifteen percent of cases have subacute IE has normal or subnormal temperatures throughout
their course (142). This is especially true for the elderly. Acute IE is marked by an extremely
high fever. With rare exception, murmurs are consistently present in subacute disease
although less than 50% of patients had previously recognized alveolar disease. The
characteristics of pre-existing murmurs do not exhibit any change until late in the course of
subacute disease. Murmurs are absent in about one-third of patients with left-sided acute IV
and two-thirds of those with either right-sided disease or mural endocarditis (143).
The dermal stigmata of valvular infection, Osler’s nodes, Janeway lesions, and splinter
hemorrhages are currently observed in only about 20% of patients. Of individuals with SBE,
40% develop joint and muscle involvement of various types (144). These include arthritis and
synovitis. They represent the immunological phenomena of this type of valvular infection.
Septic arthritis may develop from the BSI of staphylococcal IE. Splenomegaly is present in less
than 30% of cases, usually acute ones. When candidemia/candidal IE is suspected and
ophthalmological consult should be called for evaluation of the patient for the presence of
Candidaemboli and endophthalmitis. Specific eye findings can occur in approximately 30%
of patients. Such an examination is helpful both for diagnosis and also length and type of
treatment (145). For further physical findings of IE refer to Table 7.
Laboratory/Imaging Tests
The diagnostic hallmark, of all types of IE, is the presence of a continuous bacteremia. This
may be defined as two sets of blood cultures, drawn at least 12 hours apart, that grow out the
same organism. At least three out of four blood cultures, positive for the same organism with
the first and last sets separated by at least one hour also define a continuous BSI (146). In the
case of ABE, the time span for obtaining blood cultures should be shortened to one-half hour
because of the imperative in beginning appropriate antibiotic therapy. In the case ofS. aureus
BSI, the time to positivity of the blood culture is also an important parameter. Growth of this
organism within 14 hours of culture indicates those patients with an increased likelihood to
have valvular infections as the source of the BSI as well as having a greater amount of
complications such as metastatic infection (147) In culture positive IE, three sets of blood
cultures will detect the pathogen in grater than 99% of cases (148). This figure applies
primarily toS. viridansIE. When diagnosing possible PVE, five sets of blood cultures should be
drawn. The BSI of PVE may not be continuous in up to 10% of cases (149). In addition, multiple
blood cultures are helpful in differentiating infection with CoNS from contamination with this
organism. At least 64% of patients who have received prior antibiotics will have false negative
blood cultures (150). The longer the duration of antibiotic administration, the greater the length
of time that the blood cultures remain negative. Under these conditions, the blood cultures
should be obtained at least to 48 hours after the antimicrobial agent has been discontinued
232 Brusch