458
U N I T 5
Circulatory Function
As the lesions grow, they cause valve destruction and
dysfunction such as regurgitation, ring abscesses with
heart block, and perforation. The loose organiza-
tion of these lesions permits the organisms and frag-
ments of the lesions to form emboli and travel in the
bloodstream, causing cerebral, systemic, or pulmonary
emboli. The fragments may lodge in small blood ves-
sels, causing small hemorrhages, abscesses, and infarc-
tion of tissue. The bacteremia also can initiate immune
responses thought to be responsible for skin manifes-
tations, polyarthritis, glomerulonephritis, and other
immune disorders.
6,27
Manifestations.
Signs and symptoms of IE can include
fever and signs of systemic infection, development of a
new heart murmur, change in the character of an exist-
ing heart murmur, and evidence of embolic distribu-
tion of the vegetative lesions.
27
In the acute form, the
person is likely to develop a high fever accompanied
by chills. In the subacute form, the fever usually is
low grade, of gradual onset, and frequently accom-
panied by other systemic signs of inflammation, such
as anorexia, malaise, and lethargy. Small petechial
hemorrhages frequently result when emboli lodge in
the small vessels of the skin, nail beds, and mucous
membranes. Splinter hemorrhages (i.e., dark red lines)
under the nails of the fingers and toes are common.
27
Cough, dyspnea, arthralgia or arthritis, diarrhea, and
abdominal or flank pain may occur as the result of
systemic emboli.
Diagnosis and Treatment.
Infective endocarditis con-
tinues to pose major challenges in terms of diagnosis
and treatment.
27–31
The blood culture remains the most
definitive diagnostic procedure and is essential for guid-
ing the treatment. However, the indiscriminate use of
antibiotics has made identifying the causative organism
much more difficult. Negative blood cultures can occur
in up to 30% of cases of IE, delaying diagnosis and
treatment and consequently having a profound effect
on outcome.
29
This may result from the prior admin-
istration of antibiotics, because the infection is grow-
ing slowly, or because it is challenging to culture in a
laboratory (i.e., the organism requires a special culture
medium). Transthoracic and transesophageal echocar-
diography are the primary techniques for detection of
vegetation and cardiac complications resulting from IE
and are important tools in the diagnosis and manage-
ment of the disease.
27
Treatment of IE focuses on identifying and eliminat-
ing the causative microorganism, minimizing the resid-
ual cardiac effects, and treating the pathologic effect of
emboli. The choice of antimicrobial therapy depends
on the organism cultured and whether the infection
involves a native or prosthetic valve. The widespread
emergence of multidrug-resistant organisms, including
S. aureus,
poses a serious challenge in the treatment of
IE. In addition to antibiotic therapy, surgery may be
needed for unresolved infection, severe heart failure,
and significant emboli.
Prevention of IE through the use of prophylactic
antibiotics is controversial. The current recommenda-
tions conclude that only a very small number of IE cases
might be prevented by antibiotic prophylaxis for den-
tal procedures. Therefore, prophylaxis is recommended
only for patients with predisposing congenital or val-
vular disorders undergoing select dental and surgical
procedures.
31,32
Rheumatic Heart Disease
Rheumatic fever (RF) is an immune-mediated, multi-
system inflammatory disease (involving heart, skin, and
connective tissue) that occurs a few weeks after a group
A (
β
-hemolytic) streptococcal (GAS) pharyngitis (sore
throat) in children and young adults. It rarely occurs with
streptococcal infections at other sites (e.g., skin).
6
Acute
rheumatic heart disease (RHD) is the cardiac manifesta-
tion of RF and is associated with inflammation of all
three layers of the heart (myocardium, pericardium, and
endocardium including the heart valves). Chronic defor-
mity and impairment of one or more of the heart valves
is the most important consequence of RHD. Although
RF and RHD are rare in developed countries, the disor-
ders continue to be major health problems in underde-
veloped countries, where inadequate health care, poor
nutrition, and crowded living conditions still prevail.
33
Data from recent studies that used echocardiography to
screen for RHD indicate that the prevalence of RHD is
increasing in these regions. As a result, there has been
an increased awareness and interest in RF and RHD.
34
Pathogenesis.
The pathology of RF does not involve
direct bacterial infection of the heart. Rather, the time
frame for development of symptoms relative to the onset
of pharyngitis and the presence of antibodies to the GAS
organismstrongly suggests an immunologic response.
33–35
It is thought that antibodies directed against the M pro-
tein of certain strains of streptococci cross-react with
glycoprotein antigens in the heart, joints, and other
FIGURE 19-12.
Gross pathology of subacute bacterial
endocarditis involving the mitral valve. Left ventricle of the
heart has been opened to show mitral valve fibrin vegetations
due to infection with Haemophilus parainfluenza. Autopsy.
(From the Centers for Disease Control and Prevention Public
Health Images Library No. 851. Courtesy of Edwin P. Ewing Jr.)
