Page 662 - Cardiac Nursing

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CHAPTER
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S S S S Sudden Cardiac Death and Cardiac Arrest t t
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Donna Gerity
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Su S dden cardiac deathh (SCD) is a majjor cliniical a dnd public hhe lalth fa factors per the 26-year folloow-up of the Framingham Study. SCCD
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pr problem in the United States. Thee incidence of SCD is difficult to do does appearr tto bee increasing in women. From 1989 to 1999, SCD
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measure due to inconsistent methodology in classifying deaths. increased by 21% ammong women aged 35 to 44 years in the
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Un
V Va irious es imates of annual SCDD events inn thee Unit ded States range Uniit ded States. During this same time frame there was a 2.8% de-
it
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from 200,000 to 450,000. The most widely used estimate is in the cline among men of the same age group. 1,9 Risk profiling for
range of 300,000 to 350,000 deaths annually. Even with signifi- CAD is useful for identifying populations and individuals at risk,
cant advances in management of coronary artery disease (CAD), but does not identify an individual patient at risk for SCD. The
and the treatment of heart failure, the overall incidence has re- inability to identify individuals is a major reason why SCD
1
mained unchanged as our population ages. CAD is present in as remains an important public health problem. 10
many as 80% of those individuals who experience SCD. Autopsy There are several different arrhythmia mechanisms responsible
studies show that 50% of these sudden death patients have acute for SCD. The most common arrhythmia leading to SCD appears
changes in coronary status, such as plaque, rupture, or thrombus. 2 to be ventricular tachycardia (VT) accelerating into ventricular
Survival rates for out-of-hospital sudden cardiac arrest (SCA) vic- fibrillation (VF), often followed by asystole or pulseless electrical
tims are low, with only 2% to 25% surviving to discharge in the activity (PEA). Acquired structural and functional changes that
United States. Those survivors of SCA have a high risk for future occur in a diseased heart, and genetic factors may contribute to
events. Therefore, the aim at decreasing SCD is to better identify sudden death. However, the mechanism that produces the poten-
and treat potential victims of SCD. Future events will be mini- tially fatal arrhythmia among patients with CAD is difficult to de-
mized if the incidence of CAD is reduced and primary and sec- fine. 11,12
ondary prevention is provided. 3,4 The episode could be caused from pure ischemic injury be-
cause of occlusion of a major artery in a patient with a normal
ventricle in whom VF develops in the first minutes of an acute in-
DEFINITION OF SUDDEN DEATH farction. The other type of mechanism is one in which a patient
with a previous myocardial infarction (MI) has postinfarction
scarring that provides the anatomic substrate for VT that leads to
SCD is defined as an unexpected death caused by cardiac causes
hemodynamic collapse and SCD. Patients could also have com-
that occurs within 1 hour of symptom onset. The person may or
plex substrates consisting of dense scar tissue with aneurysms or
may not have known pre-existing heart disease. Cardiac arrest,
other areas where disorganized arrhythmias predominate. This
usually caused by cardiac arrhythmias, is the term used to describe
complex interaction and multiplicity of influences that occur in a
the sudden collapse, loss of consciousness and loss of effective cir- 2,7
culation that precedes biologic death. 5,6 A subclassification of cardiac arrest episode differ for all patients.
sudden death uses the term instantaneous death, a death with im-
mediate collapse without preceding symptoms. Other causes of Structural Abnormalities
death may also be instantaneous, such as stroke, massive pul-
monary embolism, or rupture of an aortic aneurysm. It is also im- Coronary Heart Disease
CHD is the major structural abnormality found in most SCA vic-
portant to note that not all arrhythmic deaths are sudden. A pa-
tims. In 80% of patients who have had an SCA, CAD is present.
tient may be successfully resuscitated from a cardiac arrest but 10,13
may die days later from complications. 7 SCA is often the first manifestation of CHD. Pathology stud-
ies of SCD patients have shown that coronary atherosclerosis is
the major predisposing cause. Plaque rupture and plaque erosion
are the underlying pathologies in the majority of cases of SCD.
PATHOPHYSIOLOGY AND Evidence shows a difference in the mechanism of MI and death
CAUSE OF SCA between men and woman. Men tend to have coronary plaque
rupture, while women tend to have plaque erosion. 14 Data from
The epidemiology of SCD tends to follow that of coronary heart the Nurses’ Health Study of 121,701 women have shown that
disease (CHD). The incidence of SCD increases with the aging 94% of women who had SCD had one risk factor for heart dis-
9
population in both men and women, whites and nonwhites, just ease. The evolution and clinical manifestation of CHD leading
as ischemic heart disease increases. SCD occurs 75% more often to SCA has been identified as four separate stages (Fig. 27-1). The
first stage is atherogenesis, which is the beginning of plaque forma-
H
in
intra
yper
in men. Hypertension, left ventricular hypertrophy (LVH), intra- first stage is ather ogenesis which is the beginning of plaque forma
tension
men
(L
tr
ophy
hyper
left
VH)
entricular
v
ventricular conduction defect, hypercholesterolemia, vital capac- tion and occurs over a long period of time. This stage should be
ity, smoking, relative weight, and heart rate were all noted as risk thought of as the stage that determines risks for CHD. The
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