(Stroke. 2000;31:2068.)
© 2000 American Heart Association, Inc.
Original Contributions |
From the Departments of Clinical Neurology (M.S., H.K., C.S.), Internal Medicine IV, Division of Intensive Care Medicine (C.M.), and Emergency Medicine (M.H., J.K., F.S.), University of Vienna, Vienna, Austria.
Correspondence to Mark Schiefermeier, PhD, Department of Clinical Neurology, University of Vienna, Währinger Gürtel 18-20, A-1090 Vienna, Austria. E-mail mark.schiefermeier{at}univie.ac.at
| Abstract |
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MethodsEighty patients with cardiac arrest were investigated prospectively for their apoE genotype. Epidemiological data were assessed according to recommended guidelines. Patients were divided into 2 groups, ie, with the apoE 3/3 genotype present or absent, and tested for differences in survival and neurological outcome. Further statistical analysis with respect to survival and neurological outcome was performed by using a stepwise logistic regression analysis.
ResultsPatients with the apoE 3/3 genotype had a significantly higher survival rate (64% versus 33%, P=0.007) and more often a favorable neurological outcome (55% versus 27%, P=0.013) compared with patients with other apoE genotypes. The apoE 3/3 genotype was shown to be a substantial predictive factor for a favorable neurological outcome (odds ratio 3.2) and was, apart from other essential factors, predictive for survival (odds ratio 4.4) after cardiopulmonary resuscitation.
ConclusionsThese data give evidence that patients with the apoE 3/3 genotype have a better chance of recovery after cardiopulmonary resuscitation than do patients with apoE genotypes other than 3/3.
Key Words: apolipoproteins E heart arrest polymorphism resuscitation stroke outcome
| Introduction |
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The cessation of blood flow induces ischemic cell damage and a
complex cascade of postischemic injury. Several organs can
withstand complete ischemia for a prolonged time because
initial cell damage is low and the ability to repair and regenerate
tissue is relatively pronounced, whereas the brain is most susceptible
to ischemic damage and has a very limited potential to
regenerate. An essential component of nerve regeneration is
apolipoprotein E (apoE), which serves as the major carrier of
cholesterol, cholesterol esters, and lipids in
the nervous system. It has been proposed that apoE production
is stimulated by nerve injury to preserve the integrity of cell
membranes.9 10 Moreover, it has been shown that
apoE-deficient knockout mice have a worse neurological outcome after
cerebral ischemia than do wild-type mice.11 The
polymorphic structure of the human apoE gene in particular gave
rise to intensive investigation of apoE. Two point mutations of the
human apoE gene cause 3 apoE isoforms (apoE 2, apoE 3, and apoE 4) and
consequently, 6 apoE genotypes. Initially, the apoE
4
allele was identified as a risk factor for the development of
Alzheimers disease.12 Recently, it has been
shown that patients with the predominant, homozygous apoE 3/3
genotype have a better neurological outcome after traumatic
head injury13 14 15 16 as well as a later onset of neurological
symptoms in Wilson disease than do patients with other apoE
genotypes.17 The molecular basis of these
observations is unclear, but the hypothesis that apoE 3 contributes to
regenerative mechanisms more efficiently than do other apoE proteins
appears likely.
ApoE polymorphism may have a decisive influence on the outcome after CPR. Therefore, we attempted to clarify whether patients with the apoE 3/3 genotype have (1) a better neurological outcome and (2) a higher survival rate after CPR compared with patients with other apoE genotypes (apoE non-3/3).
| Subjects and Methods |
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Included were adults of all ethnic origins with a witnessed, nontraumatic, normothermic cardiac arrest of presumed cardiac or pulmonary origin. Patients were excluded from the study when the duration of cardiac arrest was >20 minutes and when primary CPR failed to achieve any return of spontaneous circulation within 60 minutes. Furthermore, we excluded patients with known malignancy, pregnancy, and unfavorable overall and/or cerebral performance before cardiac arrest.
Epidemiology and Laboratory
Measurements
Epidemiological data were assessed according to the recommended
guidelines (Utstein style) for uniform documentation of cardiac
arrest.18 Data were obtained through interviews with the
ambulance physicians, paramedics, bystanders, and family. The
recording of periods of time during cardiac arrest is an
estimate and cannot be determined accurately. Owing to the fact that
only 1 person was responsible for collecting the patients charts
according to the Utstein style, highly comparable data were available
for every patient. Personal interviews of the witnesses served to
reduce inaccuracy concerning the time of recognition of collapse and
the period of emergency medical activation.
Patient protocols included location (within the hospital or out of hospital); presumed etiology (cardiac or pulmonary causes) of collapse of the circulation; the initial rhythm, referring to the first recorded electrocardiographic activity (ventricular fibrillation or asystole and pulseless electrical activity); a detailed time protocol of collapse of the circulation (time to return of spontaneous circulation, no-flow time, and low-flow time); the number of defibrillations; and the cumulative amount of epinephrine administered during resuscitation. No-flow time was defined as the period from collapse of the circulation until the beginning of basic and/or advanced life support. Low-flow time was defined as the interval from the beginning of basic and/or advanced life support until the return of spontaneous circulation or termination of resuscitative efforts. Finally, the duration until the first meaningful reactivity to phonic, visual, or tactile stimulation, and in the case of death within 6 months, the interval until death, were determined. Age, sex, and typical laboratory parameters such as blood pH, plasma lactate, and plasma glucose were determined in each patient after admission to the Emergency Clinic. The apoE genotype was determined by a common polymerase chain reaction technique previously described.19 In brief, DNA was isolated from peripheral blood samples with a commercially available DNA isolation kit (Purgene, Gentra Systems). Thereafter, a 228-bp fragment of the apoE gene was amplified by polymerase chain reaction with the use of specific primers. The amplified product was cleaved with CfoI. Mutation-specific fragments were then visualized with ethidium bromide after separation by vertical polyacrylamide gel electrophoresis. ApoE genotype was determined by the genotype-specific fragment pattern.
Neurological Outcome and Survival
Neurological outcome was assessed on the basis of the cerebral
performance categories (CPCs) after 6 and 12 hours; on days 1,
2, and 7; and at months 1 and 6. CPC is based on the Glasgow overall
performance categories20 and is defined as
follows: CPC 1, conscious and alert, with normal function or only
slight disability; CPC 2, conscious and alert with moderate disability;
CPC 3, conscious with severe disability; CPC 4, comatose or in a
persistent vegetative state; and CPC 5, brain death. The main primary
outcome measure was the best-ever-achieved CPC within 6 months. A CPC
of 1 or 2 was assigned a "good neurological outcome"; a
best-ever-achieved CPC >2 within 6 months was assigned a "bad
neurological outcome." Patients who died within 6 months were
classified as nonsurvivors.
Statistical Analysis
Patients were divided into 2 groups: apoE 3/3, patients
homozygous for the apoE
3 allele, and apoE non-3/3, patients
with the genotypes apoE 4/3, apoE 2/3, apoE 4/4, apoE 4/2, and
apoE 2/2. The software package SPSS for Windows, version
8.0, was used for statistical analysis. After confirmation of a
normal distribution, we tested for differences in mean values of normal
data between the 2 groups with Students t test and in
differences of nonnormal, continuous data with the Mann-Whitney
rank-sum test. Continuous data are summarized by mean±SD. Nominal data
are given as frequencies and were compared with continuity-corrected
2 tests or Fishers exact tests when expected
cell frequencies were <5. Generally, P values <0.05 were
considered statistically significant. For multivariate
stepwise regression analysis, patients were divided according
to outcome variables into those with good or bad neurological
outcomes and those who survived or died. We tested for differences
between these groups with univariate methods (t
test, Mann-Whitney rank-sum test, and
2
analysis of contingency tables). Variables causing a
difference in the outcome variable at P<0.1 according
to the univariate analysis were included for a
stepwise backward logistic regression. Variables with a
log-likelihood ratio of P>0.05 were excluded stepwise until
each remaining variable was statistically significant. The effect
of every significant model parameter is given by its odds
ratio.
| Results |
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The apoE genotype frequency of our 80 patients did not deviate from known apoE genotype frequencies of healthy Europeans.21 22 23 Fifty-nine percent had the apoE 3/3 genotype; 30%, apoE 3/4; 6%, apoE 2/3; 3%, apoE 4/2; 1%, apoE 4/4; and 1%, apoE 2/2 genotype. Consequently, 47 patients were assigned to the group of the predominant apoE 3/3 genotype and the other 33 patients were assigned to the group non-apoE 3/3 genotype.
Patients of both groups were afflicted by a collapse of the circulation
to a comparable extent, were in similar
physiological condition, and underwent the same
emergency support procedures. Neither age or sex nor any of the
laboratory parameters such as blood pH, plasma lactate, and
plasma glucose concentrations were different in patients with the apoE
3/3 genotype in comparison with those with other apoE
genotypes (Table 1
).
Similarly, no differences were found in the frequencies of collapses of
the circulation within the hospital or out of hospital, the frequency
of resuscitation initiated with basic life support, the frequency of
ventricular fibrillation as the initial rhythm, and cardiac
or pulmonary etiology. In addition, no-flow time, low-flow
time, and time to return of spontaneous circulation as well as the
emergency procedures applied were similar in both groups (Table 1
).
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The distributions of good versus bad neurological outcome and of
survivors versus nonsurvivors in patients with the apoE 3/3
genotype and in those with a different apoE genotype
are given in Table 2
. Patients with the
apoE 3/3 genotype more often achieved a good neurological
outcome than did patients with other apoE genotypes
(P=0.013). The duration until the first period of permanent
consciousness was shorter in patients with the apoE 3/3
genotype than in patients with other genotypes (Table 1
), although statistical significance was not reached
(P=0.06). In addition, the rate of survival was greater in
patients with the apoE 3/3 genotype than in patients with other
genotypes (P=0.007).
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Because apoE 4 has been implicated in neurodegenerative diseases, the
proportion of patients with a poor neurological outcome and with an
apoE
4 but without an apoE
2 allele (and vice versa) was of
interest. Therefore, we analyzed the data in more detail by
disregarding those patients with the apoE 4/2 genotype and
dividing the rest of the group of apoE non-3/3 patients into those with
the apoE 3/4 or the apoE 4/4 genotype and those with the apoE
2/3 or the apoE 2/2 genotype. In brief, 28% of the patients
with the apoE 3/4 or the apoE 4/4 genotype (P=0.027)
and 17% of the patients with the apoE 2/3 or the apoE 2/2
genotype (P=0.100) achieved a good neurological
outcome compared with 55% of the patients with the apoE 3/3
genotype. Similarly, 36% of the patients with the apoE 3/4 and
apoE 4/4 genotypes (P=0.024) and 17% of the
patients with the apoE 2/3 and apoE 2/2 genotypes
(P=0.071) survived compared with 64% of the patients with
the apoE 3/3 genotype. Although the number of patients with
apoE
2 and no apoE
4 allele was too small to reach
statistical significance in this separate analysis, these data
strongly suggest that the presence of both alleles are unfavorable
for patients outcome.
Logistic regression analysis for neurological outcome (good,
CPC 1 to 2; unfavorable, CPC 3 to 5) initially included the following
parameters: a constant, cardiac arrest within or out of the
hospital; initial rhythm; the cumulative amount of epinephrine
administered; time to return of spontaneous circulation; no-flow time;
blood pH and lactate concentration on admission; and presence or
absence of the apoE 3/3 genotype. The final model
parameters are given in Table 3
. The parameter "cardiac
arrest within or out of the hospital" was the last
parameter removed from the model (P of
log-likelihood ratio=0.066). Independent, significant, predictive
parameters were the cumulative amount of
epinephrine administered, the initial rhythm, and the apoE 3/3
genotype. The relative chance (odds ratio) of having a good
neurological outcome increased 3.5-fold when the patient had the apoE
3/3 genotype and decreased by 0.74-fold per milligram of
epinephrine administered. Patients with an initial
ventricular fibrillation had a 5.3-fold relative chance for
a good neurological outcome compared with patients with asystole or
pulseless electrical activity. Therefore, the type of initial rhythm,
the apoE genotype, and the cumulative amount of
epinephrine administered were essential, independent
determinants of neurological recovery.
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Logistic regression analysis for general outcome
(survival or death) initially included the following
parameters: a constant, cardiac arrest within or out of the
hospital; initial rhythm; the cumulative amount of epinephrine
administered; time to return of spontaneous circulation; no-flow time;
cardiac or pulmonal etiology of cardiac arrest; age; and the presence
or absence of the apoE 3/3 genotype. The final model
parameters are given in Table 3
. Independent,
significant, predictive parameters for survival were
cardiac arrest within or out of the hospital, the cumulative amount of
epinephrine administered, cardiac or pulmonary causes
of cardiac arrest, age, and the apoE 3/3 genotype. The chance
of survival increased 12.9-fold when a patient was afflicted with
cardiac arrest within the hospital, 8.3-fold when the cause of cardiac
arrest was cardiac rather than pulmonary, and 4.4-fold when the
patient had the apoE 3/3 genotype and decreased by 0.81-fold
per milligram of epinephrine administered and by 0.96-fold per
year of age.
| Discussion |
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Despite considerable improvement in the treatment of cardiac arrest, many resuscitated patients suffer from the consequences of irreversible damage to the nervous system. Although reinstallation of the circulation with the least possible delay is most important in preventing persistent neurological damage, many other factors may influence the patients neurological outcomes. We were interested in whether a genetic factor in patients with early and adequate treatment of cardiac arrest had an impact on their neurological outcome and survival rate. Therefore, this study was designed to investigate the influence of the apoE genotype in well-characterized patients without a considerably prolonged cardiac arrest, without traumatic head injury, and without cerebral impairment before cardiac arrest. These selection criteria may also explain the relatively good outcome of our patients and may limit the observations of this study to patients who meet these selection criteria.
The outcome of patients with cardiac arrest can be predicted by various parameters. The identification of essential, singular observations is hampered by the fact that 1 parameter may be reflected in part by another. For example, in witnessed cases of cardiac arrest, most probably basic or advanced life support takes place early, resulting in a short no-flow time. A short no-flow time is regarded as highly predictive of survival. We attempted to identify the most reliable predictive parameters that described the outcome of our patients best through a transparent procedure for both models. Therefore, we included factors in the multivariate analysis in the order of their univariate test significance and excluded them from the model when they did not strictly contribute to the prediction of outcome in the multivariate model. In this study, the time to return of spontaneous circulation was correlated with the amount of epinephrine administered, which can be explained by the fact that prolonged CPR usually requires application of higher doses of epinephrine. However, the amount of epinephrine administered appeared to be a better predictor of neurological outcome, as well as survival, than did the time to return of spontaneous circulation.6 Apart from the presence of the apoE 3/3 genotype, ventricular fibrillation was highly predictive of a good neurological outcome. It has been argued that in patients with ventricular fibrillation, a small amount of perfusion is present. In contrast to the model for neurological outcome, the absence of ventricular fibrillation as the initial rhythm was not as crucial for survival. Young patients with the apoE 3/3 genotype, a low cumulative amount of administered epinephrine, and a cardiac etiology of cardiac arrest appear to have had an increased chance for survival. Eight of 41 survivors had a poor neurological outcome, whereas only 2 of 35 patients with a good neurological outcome died within 6 months. Obviously, progress in medical treatment enables survival after CPR in some cases but unfortunately, not neurological recovery when the central nervous system is injured beyond a certain extent.
ApoE, the major apolipoprotein of the nervous system, plays a central role in the mobilization and distribution of cholesterol, cholesterol esters, and other lipid structures. ApoE expression increases substantially after injury of nervous tissue,9 10 and apoE concentration is elevated in the cerebrospinal fluid of patients with neurological diseases.24 25 It has been proposed that apoE is secreted locally by macrophages, astrocytes, and oligodendrocytes in response to nerve degeneration to initiate cholesterol-phospholipid recycling.9 10 ApoE synthesis is stimulated by oxidized LDLs in macrophages.26 In the absence of apoE, as in the case of apoE-knockout mice, survival rate and neurological recovery are markedly reduced after cerebral ischemia.11 In addition, these mice are more susceptible to oxidative stress, as shown by increased plasma and lipoprotein lipid peroxidation.27 In vitro studies have shown that apoE itself protects against peroxidative stress by mechanisms that may involve the binding of certain metals, thus blocking the generation of cytotoxic radicals.28
The intention of this study was to investigate the influence of apoE
polymorphism on neurological outcome after CPR, because several
lines of evidence had indicated that the extent of neurorepair,
neuroregeneration, and neuroprotection depended on the apoE isoforms
present. ApoE 3 is the most common apoE isoform. Homozygosity for
apoE 3 in humans reduces the risk for the development of late-onset
dementia of the Alzheimer type,12 may protect
against early vascular morbidity,29 is associated with a
better neurological outcome after head trauma13 14 15 16 and
intracerebral hemorrhage,22 and
delays the onset of neurological symptoms in Wilson
disease.17 Human apoE 3transgenic mice recover better
from focal ischemia than do human apoE 4transgenic
mice.30 Moreover, in vitro investigations have revealed
that apoE 3 promotes axonal sprouting.31 Humans with an
apoE
4 allele show mild
hypercholesterolemia and have lower apoE plasma
concentrations.23 In contrast to apoE 3, the presence of
the apoE
4 allele favors the development of Alzheimers
disease and has a negative impact on the effects of the in vivo and in
vitro parameters in the investigations mentioned above. The
role of apoE 2 has not yet been clarified. Most studies have not
investigated or focused on the apoE
2 allele because of its rare
occurrence, and other studies have produced conflicting results. ApoE 2
is associated with a reduced risk for the development of
Alzheimers disease.12 32 Although the presence
of an apoE
2 allele has favorable effects on the lipid profile
and cardiac disease,21 23 it may also be a risk factor for
promoting microangiopathy-related cerebral damage.21 29 32
ApoE 2 acts as an antioxidant in vitro.28 Nevertheless,
heterozygous apoE 2 patients with Wilson disease develop neurological
signs of early copper toxicity.17 In the present
study, patients with at least 1 apoE
2 as well as patients with at
least 1 apoE
4 allele had a poor neurological outcome and a
lower survival rate after CPR compared with patients homozygous for the
apoE
3 allele. Therefore, it can be suggested that our results
are in part a reflection of the reduction or absence of the apoE 3
isoform and are not exclusively caused by the presence of the
potentially neurodegenerative apoE 4 isoform. Nonetheless, for a better
understanding of apoE genotypespecific effects, further
studies based on a larger number of subjects as well as further
investigations with molecular biological techniques are required. Among
other parameters, the singular effects of each isoform
should be investigated by focusing on apoE 3 homozygous patients and
the extremely rare homozygous genotypes apoE 4/4 and apoE
2/2.
The results of this study identify apoE as a genetic factor modulating outcome after CPR. Although independent studies have elucidated some biochemical allele-specific effects of the apoE gene, the molecular basis of our results is still unclear. Further investigations are required to answer the question of whether the neuroprotective and neuroregenerative properties of apoE can be exploited for therapeutic purposes. We conclude that patients with the apoE 3/3 genotype may benefit from their genetic background during their recovery after cardiac arrest.
| Acknowledgments |
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Received February 28, 2000; revision received May 15, 2000; accepted July 6, 2000.
| References |
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4 allele is associated with deposition of amyloid
ß-protein following head injury. Nat Med. 1995;1:135137.[Medline]
[Order article via Infotrieve]
4 associated with chronic traumatic
brain injury in boxing. JAMA. 1997;278:136140.[Abstract]
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