Page 757 - Cardiac Nursing

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C HAPTER 30 / Pericardial, Myocardial, and Endocardial Disease 733
Etiology
ENDOCARDIAL DISEASE Streptococci and staphylococci account for 80% to 90% of IE cases
in which identification of the organism is made. 92 Staphylococcus
Infective Endocarditis aureus is an important cause of IE, as the course is often fulmi-
nant, and this is frequently a nosocomial infection. 92 Enterococ-
IE is a disease in which infective organisms invade the endothelial cus may cause up to 15% of IE cases. Several other infectious or-
92
lining of the heart, usually involving one or more valves. The en- ganisms can also cause IE.
docardium covers the valves and surrounds the chordae tendineae.
Recently, the definition of IE has been expanded to include an in- Pathophysiology
fection of any structure within the heart including prosthetic A complex series of events interplay to result in IE. Endothelial
valves, and implanteddevices, as well as the valves and endothe- damage appears to be the first step, followed by platelet–fibrin
92
lium. The infection that forms, an irregularly shaped echogenic deposition and formation of a lesion known as a nonbacterial
mass adherent to the endothelial cardiac surface, often on the thrombotic endocarditis. Bacteremia then allows bacterial colo-
valve of the heart, is called vegetation. 92 Destruction, ulceration, nization. Colonization allows formation of a vegetation as mi-
or abscess formation can also occur. IE is the major endocardial croorganisms adhere to the nonbacterial thrombotic endocarditis
disease. Ifleft untreated, IE is fatal. 93 lesion. 92 Many of the clinical manifestations of IE result from the
infected individual’s immune response to the microorganism. 97
Types Structural abnormality in a valve is commonly seen in IE. Mi-
tral valve prolapse, aortic valve disease, and congenital heart dis-
Native Valve Endocarditis. Native valve endocarditis (NVE), 92
the most common type, is an infection seen in patients without ease exist in a large number of patients with IE. Mechanical and
prosthetic valves can also become infected.
prosthetic valves, but who usually have valvular or heart disease
that predisposes them to IE.
Assessment Findings
The Intravenous Drug User. NVE is a severe complication The diagnosis of IE is based on clinical signs and symptoms, and
of IV drug use. It is responsible for 5% to 20% of hospital ad- demonstration of continued bacteremia. 92 In 1994, Durack
missions, and 5% to 10% of total deaths in those that use IV et al. 99 proposed a set of diagnostic criteria for the diagnosis of IE
drugs. 92,94 IE in IV drug users is thought to be caused by infec- that subsequently became known as the Duke criteria. According
tion introduced through contaminated needles or drugs. IE in to the Duke criteria, persistent bacteremia with organisms typical
these patients often involves the tricuspid valve. 92 In the IV drug for endocarditis and an oscillating mass on a valve (vegetation)
user with IE, the valves were normal before infection in 75% to make a clinically definitive diagnosis of IE. In the course of clini-
93% of patients. 95 cal practice, the diagnosis is suspected more often than it is con-
firmed. The Duke criteria include several minor criteria that also
Prosthetic Valve Endocarditis. The clinical index for sus- suggest IE, such as predisposition, fever, vascular phenomena such
picion is much higher for prosthetic valve endocarditis (PVE), as septic pulmonary infarcts, and immunologic phenomena such
which occurs more frequently than NVE. PVE is also much more as Osler’s nodes. Transthoracic echocardiography with Doppler
likely to require surgery as part of the treatment. PVE represents
flow studies should be performed in everyone suspected of having
10% to 30% of all IE.
endocarditis. In 2000, other researchers proposed several modifi-
Infected Intracardiac Devices. During the 1990s there was cations to the Duke criteria, including the use of transesophageal
a large increase in cardiac device implantations, such as pacemak- echocardiogram. 100 If the clinical suspicion is high and the
ers and ICDs. Accompanying this increase was a surge in IE re- transthoracic echocardiogram is negative or inconclusive, a trans-
lated to these intracardiac devices, especially in elderly patients. 96 esophageal echocardiogram should be obtained. 100
Major criteria to diagnose IE includes at least two positive cul-
Nosocomial Endocarditis. Nosocomial endocarditis is an
tures of blood samples drawn greater than 12 hours apart, or all of
infection of the cardiac endothelium related to health care.
three or a majority of four or more separate cultures of blood, with
the first and last samples drawn at least 1 hour apart. 100 Blood cul-
Epidemiology tures should be drawn from three different sites with 1 hour be-
IE affects 15,000 patients every year and it has a mortality rate tween each draw or, if time is limited, a total of 1 hour between
approaching 40%. 92 Rheumatic heart disease was the most com- the first and the last draw. Blood cultures isolate the organism,
mon underlying condition predisposing an individual to endo- and positive cultures over time demonstrate true persistence.
carditis in developed countries, and this remains a common con- Meticulous site preparation is essential to avoid contamination. 101
97
dition in developing countries. Despite advances in health care, Blood cultures can be negative in up to 15% of patients meeting
the incidence of IE has not decreased over the last few decades. criteria for IE diagnosis. 102 Other laboratory findings seen in IE
This apparent paradox may be explainedby an evolution in risk can include normochromic normocytic anemia, elevated white
factors; while classic predisposing conditions such as rheumatic blood cell count, and elevated erythrocyte sedimentation rate in
heart disease have been all but eradicated, new riskfactors for IE almost all cases. 95
have emerged. These include an increasing use of various intrac- Anemia, with red blood cell indices, a low serum iron level, and
ardiac valvular prostheses and intravascular shunts, grafts, and low serum iron-binding capacity, is found in 70% to 90% of pa-
other devices. 97 In a review of 26 publications, Moreillon and tients. Anemia worsens with increased duration of illness and thus
Que reported a median incidence of IE of 3.6 per 100,000. 98 In in acute IE may be absent. A leukocytosis with increased seg-
areas where there are many IV drug users, the incidence is mented granulocytes is common in acute IE. Thrombocytopenia
92
higher. The highest incidence of IE is reported in the elderly. 92 occurs only rarely. While erythrocyte sedimentation rate is elevated