From the Department of Surgery, University of California at Los Angeles
School of Medicine (W.S.M.); Department of Surgery, University of Cincinnati
Medical Center (Ohio) (R.F.K.); Department of Biostatistics, University of
North Carolina, Chapel Hill, NC (J.J.N.); and Department of Neurology, Bowman
Gray School of Medicine, Winston-Salem, NC (J.F.T.).
Correspondence to Virginia J Howard, MSPH, Research Assistant Professor of Neurology, The Bowman Gray School of Medicine, Medical Center Blvd, Winston-Salem, NC 27157-1078. No reprints available.
MethodsThe ACAS database was interrogated to determine the rate
of recurrent carotid stenosis (
ResultsOf the 825 patients randomized to the surgical arm of the
study, 720 actually underwent carotid
endarterectomy, and 645 had complete ultrasound
data. The aggregate incidence of residual and recurrent carotid
stenosis for all time intervals ranged from 12.7% to 20.4%,
depending on the positive predictive value confidence level desired.
Residual disease occurred in 4.1% to 6.5%; true, early
restenosis was found in 7.6% to 11.4%; and late
restenosis occurred in 1.9% to 4.9%. None of the traditional
risk factors showed a statistically significant effect on recurrent
stenosis. The use of patch angioplasty closure reduced overall
risk of restenosis from 21.2% to 7.1%, from 16.7% to 4.6%,
and from 27.4% to 8.2%, depending on the PPV confidence level desired
(P<0.001). Of the 136 patients judged to have recurrent
stenosis, only 8 (5.9%) underwent reoperation (only 1 for
symptoms). There was no correlation between late stroke and recurrent
stenosis.
ConclusionsCarotid endarterectomy is a
durable procedure with a low rate of true restenosis,
particularly when patch angioplasty is used to close the arteriotomy.
We then accessed the ACAS database with the following questions: (1)
What was the total number of CEAs performed in the study? (2) Of the
total number of patients undergoing CEA, how many had an initial
postoperative Doppler study that failed to normalize after CEA? (3)
What was the total number of patients with normalized postoperative
Doppler data who developed a recurrent carotid stenosis
within 18 months of follow-up as well as during the interval between 18
and 60 months? (4) Of the patients who developed recurrent carotid
stenosis, how many became symptomatic in the
distribution of the recurrent stenotic lesion? (5) Of the
patients who developed recurrent carotid stenosis, how many
required reoperation for either symptoms or continued progression to a
high-grade lesion? (6) In both unifactorial and multifactorial
analyses comparing patients with and without recurrent
stenosis, were there any correlations with the following
parameters: age, sex, hyperlipidemia,
continued cigarette smoking, diabetes mellitus, hypertension,
peripheral vascular disease, contralateral carotid
stenosis, or operation? In addition, were there any
correlations with the following technical features: patch closure,
distal endarterectomy tacking sutures, or shunt
versus no shunt? (7) Of the patients who reached an end point in the
study, either from stroke or death during the course of follow-up, how
many had residual lesions after CEA, and how many developed recurrent
carotid stenoses?
The ACAS database provided information regarding recurrent carotid
stenosis based on validated Doppler data, with 90% and a
95% PPV confidence levels. In addition, information was provided
concerning the technologists' interpretation of percent
stenosis. These 3 parameters are reported for each
of 3 time intervals: within 3 months of operation (residual disease),
between 3 and 18 months (early restenosis), and between 18 and
60 months (late restenosis).
The statistical methods used are as follows: For
univariate analysis, we used both analysis
of proportions and analysis of rates. For categorical
variables, the percentage of patients with recurrent
stenosis was compared with and without a specified
characteristic and was tested with Fisher's exact test. For continuous
variables, the mean of standard deviation of the
characteristic was compared for patients with and without recurrent
stenosis and tested for significance with a Student
t test. In addition to exploring differences in proportions,
we tested the difference of these rates for patients with and without a
specified characteristic with a
Table 1
Table 2
Table 3
Table 4
Table 5
Figure 1
One hundred thirty-six patients were judged to have recurrent carotid
stenosis as best estimate by the Doppler technician. Of
these, 8 (5.9%) underwent a second CEA. Only 1 of the 8 patients had
experienced symptoms before the second CEA, and this was a stroke 2.5
years before operation. The remaining patients underwent a second CEA
for asymptomatic recurrent carotid stenosis. Of the
8 patients undergoing repeat CEA, there were no
perioperative deaths or neurological complications.
Table 6
Continual surveillance of patients after CEA to prospectively assess
rates of recurrence was intrinsic to the design of the study.
Patients were scheduled for periodic follow-up examination with
Doppler assessment of the operated carotid bifurcation performed in
validated laboratories and measured against machine-specific cut
points, which would find the occurrence or recurrence of
hemodynamically significant stenosis in the
operated artery.14 This method of prospective
evaluation is in contrast to other reports in the literature, which
rely on retrospective data as documented with noninvasive testing in
the absence of validation of the test equipment.
The 30-day surgical morbidity and mortality associated with CEA in ACAS
has been previously carefully analyzed and reported. The
combined mortality and neurological stroke morbidity of patients
undergoing CEA was 1.5%.18 19 The present
study has demonstrated that the incidence of recurrent stenosis
as measured with a Doppler cut point with 95% PPV was 12.7%.
However, evaluation of patients within the immediate postoperative
interval indicated that the incidence of postoperative stenosis
was 4.1%. Clearly, this is not recurrence but
represents incomplete CEA, perhaps best defined as residual
disease.
The next time interval set in this study was from 3 to 18 months after
operation. In this interval the incidence of recurrent carotid
stenosis as documented by Doppler data with a 95% PPV was
7.6%. This almost certainly represents the incidence of
recurrent carotid stenosis due to myointimal hyperplasia.
The final time interval, defined within the study as 18 to 60 months,
showed a recurrent carotid stenosis rate of 1.9% with a
Doppler scenario of 95% PPV. In the final time interval we examine
the incidence of recurrent carotid stenosis probably due to
recurrent atherosclerosis. In absolute terms, 75
patients were documented to have either occurrent or recurrent carotid
stenosis with 95% PPV. Eight patients underwent repeated CEA,
7 of which were done for asymptomatic lesions. Therefore,
the incidence of recurrent carotid stenosis in the ACAS
patients was quite low, and the number of patients actually undergoing
repeated CEA was quite small.
Risk factor analysis for recurrent carotid stenosis
failed to document any particular characteristic that was associated
with a high incidence of recurrence. Previous reports have
suggested that female sex, hyperlipidemia, and
continued cigarette smoking were associated with an increased incidence
of recurrence compared with patients who did not have those
factors.5 20 21 22 We were unable to confirm
this, possibly because of insufficient sample size to reach statistical
significance.
Finally, an analysis of technical factors revealed that those
patients whose arteriotomies were closed with patch angioplasty had a
statistically significant lowering of the incidence of recurrent
carotid stenosis compared with those patients undergoing
primary arterial closure. When a Doppler cut point with
95% PPV for the presence of a hemodynamically
significant stenosis was used, the overall incidence of
recurrent carotid stenosis in patients closed with patch
angioplasty was 4.52% compared with an incidence of recurrent carotid
stenosis of 16.97% in patients undergoing primary
arterial closure. This difference was significant at a
P value of <0.001. In subset analysis, this
difference was apparent at all 3 time intervals. Thus, the percentage
of patients with occurrent or residual carotid stenosis, as
documented by an abnormal Doppler study within the first 90 days of
operation, was 1.1% in patients with patch closure compared with 5.7%
in patients with primary closure. At the time interval 30 days to 18
months, the incidence of true recurrent carotid stenosis in
patients undergoing patch angioplasty closure was 3.1% compared with
10.2% in patients with primary closure. Finally, in the third time
interval, 18 months to 5 years, the incidence of recurrent carotid
stenosis in patients whose arteriotomy was closed with a patch
as documented by a Doppler cut point with a 95% PPV was 0.56%
compared with 2.8% in patients with primary closure.
The benefit of patch angioplasty closure has been consistently
debated in the literature. Some studies have failed to show a
difference, while other studies have showed a marked difference in
favor of patch closure.6 8 9 10 11 12 23 24 25 Others have
suggested that the apparent benefit of patch angioplasty is most
readily seen in the previously defined high-risk groups, which
comprised patients with small arteries, female sex, or continued use of
tobacco.5 26
This present report suggests that patch angioplasty is beneficial
to all groups since we were unable to demonstrate any specific risk
factor that was associated with a higher incidence of recurrent carotid
stenosis. Specifically, female sex, continued use of tobacco,
and other factors, including hyperlipidemia, were not
associated with an increased risk of recurrent stenosis in this
study. However, all patients had a lower recurrence rate when
patch angioplasty was used as opposed to primary closure, even after
simultaneous adjustment for age, sex, and other
covariables. While some studies involving individual institutions
or single surgeons have failed to show a difference between patch
angioplasty and primary closure, it is clear that ACAS, which is a
multicenter study involving multiple surgeons, provides important data
in favor of patch angioplasty that is more generally applicable to the
surgical community as a whole.
Received May 26, 1998;
revision received July 22, 1998;
accepted July 22, 1998.
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5.
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6.
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© 1998 American Heart Association, Inc.
Original Contributions
Recurrent Carotid Stenosis
Results of the Asymptomatic Carotid Atherosclerosis Study
![]()
Abstract
Top
Abstract
Introduction
Subjects and Methods
Results
Discussion
References
Background and PurposeWe sought
to determine the incidence of recurrent carotid stenosis in
patients in the Asymptomatic Carotid
Atherosclerosis Study (ACAS) who had undergone carotid
endarterectomy and were prospectively followed with
Doppler ultrasound for up to 5 years.
60%) based up
angiogram-validated Doppler data, with a 90% and a 95% positive
predictive value, as well as information concerning the technologists'
interpretation of percent stenosis. These 3
parameters are reported for each of 3 time intervals:
within 3 months of operation (residual disease), between 3 and 18
months (early restenoses), and between 18 and 60 months (late
restenosis).
Key Words: angioplasty carotid endarterectomy carotid stenosis prospective studies
![]()
Introduction
Top
Abstract
Introduction
Subjects and Methods
Results
Discussion
References
Carotid endarterectomy (CEA) is now a
proven treatment for the prevention of stroke in both
asymptomatic and symptomatic patients with
hemodynamically significant
stenoses.1 2 3 4 The intermediate and
long-term durability of the procedure may be affected by the incidence
of recurrent carotid stenosis due to either myointimal
hyperplasia or recurrent atherosclerosis. The incidence
of recurrence has been quite variable, ranging from <2.0%
to as much as 30%.5 6 7 8 9 10 11 12 However, most reports
have been retrospective analyses. The Asymptomatic
Carotid Atherosclerosis Study (ACAS) had as one of its
primary objectives to define the true incidence and consequence of
recurrent carotid stenosis after CEA.13
Thus, data acquisition concerning recurrence is prospective and
is made possible by the use of preoperative and follow-up Doppler
ultrasound studies in validated laboratories. Machine-specific cut
points were defined, yielding information with both 90% and 95%
positive predictive value (PPV) concerning stenoses of
60%.14 15 16 The follow-up protocols also
provide for surveillance of recurrent symptoms and the need, if any,
for reoperation as a result of recurrent carotid stenosis. The
objective of this report will be to document the true incidence of
restenosis and frequency of reoperation secondary to recurrent
carotid stenosis. In addition, we have analyzed risk
factors, including technical considerations, that may correlate with
recurrent stenosis.
![]()
Subjects and Methods
Top
Abstract
Introduction
Subjects and Methods
Results
Discussion
References
Participation in ACAS required that each institution have the
individual Doppler instruments in their vascular laboratories
validated by a single group of experts in ultrasound, biostatistics,
and arteriography. This was accomplished by submitting 50 consecutive
angiograms from patients with carotid stenoses together with
the corresponding Doppler velocity data. These data made it
possible to assign machine-specific Doppler cut points for both
90% and 95% PPV to correlate with a diameter-reducing
stenosis of
60%. The variability of Doppler cut points
among participating institutions has previously been
reported.17 However, the cut point
consistency for individual institutions has been validated,
thus emphasizing the importance of an individual institution to
establish and validate its own Doppler data as criteria for
diagnosing hemodynamically significant carotid
stenosis. The 95% PPV Doppler cut point was used as a
single entry criterion for patients in ACAS, whereas the 90% PPV
Doppler-specific cut point was used in combination with a positive
Gee-oculopneumoplethysmography study for patient entry. All
patients randomized to the surgical arm of the study also had a carotid
angiogram confirming that a lesion of
60% stenosis was
present. Therefore, a preoperative Doppler value confirmed by
angiography was available for each patient. After CEA, all patients
were required to have a follow-up Doppler study within 3 months of
operation, every 6 months thereafter for the next 2 years, then
annually for years 3 through 5.13 14 If a
patient's Doppler data failed to normalize after CEA, we defined
that as residual disease or incomplete CEA. Recurrent carotid
stenosis was diagnosed for patients whose Doppler data
returned to normal after CEA but who, during the course of follow-up,
developed a Doppler velocity profile that reached or exceeded the
machine-specific cut point for patients at that institution. This would
indicate that the patient had developed a recurrent diameter-reducing
stenosis of
60%.
2 statistic.
In this formulation the statistic is based on an underlying Poisson
distribution. Furthermore, for categorical variables we compared
the difference in the probability of recurrent stenosis by
Kaplan-Meier (product-limit) survival analysis for patients
with and without a specified characteristic. Here, survival refers to
nonrecurrence of stenosis. Statistical significance was
tested with the log-rank statistic. After determining
univariate associations of factors with recurrent
stenosis, we performed multivariate
analysis to determine independence of associations. For
analysis of proportions, we used logistic regression to
calculate the odds ratio and a 95% CI of developing recurrent
stenosis for each factor identified from the
univariate analysis as potentially predictive,
first controlling for age and sex only and then, in
multivariate mode, simultaneously
controlling for all potential predictors. Similarly, for rates, we used
proportional hazard regression to calculate the rate ratio or risk
ratio and the 95% PPV confidence level of developing recurrent
stenosis for each factor identified from the
univariate analysis as potentially predictive,
controlling for age and sex, and then, in a separate model for all
factors, simultaneously controlling for all potential
predictors.
![]()
Results
Top
Abstract
Introduction
Subjects and Methods
Results
Discussion
References
Eight hundred twenty-five patients were randomized to the surgical
arm of the study. Of these, 724 were prepared to proceed with
operation. Four patients suffered a major stroke as a result of
preoperative angiography and did not proceed with surgery. Therefore,
720 patients actually underwent CEA. Six hundred sixty-seven patients
completed sufficient follow-up to evaluate recurrent stenosis
on the basis of technician estimate: 645 on the basis of 90% PPV and
591 on the basis of 95% PPV.
summarizes information
concerning patients who were randomized to the surgical arm and met
criteria for stenoses
60%. In addition, the table provides
information concerning patients who received
1 follow-up Doppler
study.
View this table:
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Table 1. Number of ACAS Patients Randomized to Surgery,
Receiving Surgery, and Having Doppler Measurements on
ACAS-Validated Doppler Machine
provides overall data concerning
the combination of residual and recurrent stenosis for all time
intervals. The incidence ranged from 12.7% to 20.4% depending on the
criterion used.
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[in a new window]
Table 2. Number and Percentage of Patients With Recurrent
Stenosis at Overall Follow-Up for 2 PPV Scenarios and Estimate
of Stenosis by Doppler Technician
summarizes the number and
percentage of patients with residual or recurrent carotid
stenosis as a function of the follow-up interval and expresses
them for two PPV scenarios and the best estimate of stenosis by
the Doppler technician. The incidence of residual carotid
stenosis, incompletely treated by operation, ranged from 4.1%
to 6.5% depending on the criterion used. The second time interval,
which ranges from 3 to 18 months after operation, expresses the
incidence of true, early recurrent carotid stenosis, that is,
patients who normalized after operation but developed a
hemodynamically significant recurrence during
this interval. This ranged from 7.6% to 11.4% depending on the
criterion used. The final time interval, ranging from 18 to 60 months,
includes patients whose Doppler data normalized after operation and
who remained normal until this time interval. The percentage of late
recurrent stenosis ranged from 1.9% to 4.9% depending on the
criterion used.
View this table:
[in a new window]
Table 3. Number and Percentage with Residual and Recurrent
Stenosis, by Follow-Up Period, for 2 PPV Scenarios and Estimate
of Stenosis by Doppler Technician
presents the
proportion of recurrent stenosis for known risk factors
previously reported to be associated with recurrent carotid
stenosis. Of the 15 potential risk factors tested, only the use
of patch angioplasty made a statistically significant difference in the
incidence of recurrent carotid stenosis. At 95% PPV, 16.7% of
patients without a patch experienced recurrent carotid
stenosis, whereas only 4.6% of patients with patch angioplasty
closure experienced the same problem (P<0.001). Other
previously reported factors related to recurrent carotid
stenosis, including continued smoking, female sex, and
hyperlipidemia, failed to show statistical
significance.
View this table:
[in a new window]
Table 4. Percentage of Surgical Group Patients With Recurrent
Stenosis, by Characteristic, for 2 PPV Scenarios and Estimate
of Stenosis by Doppler Technician
shows a similar
analysis, but for probability of recurrent carotid
stenosis; a Kaplan-Meier statistical analysis compares
patients with and without selected characteristics. Comparisons are
made for 2 PPV scenarios and an estimate of stenosis by the
Doppler technician. None of the traditional factors showed a
statistically significant effect on the incidence of recurrent carotid
stenosis. Additionally, Table 5
examines technical features
associated with CEA, including the use of patch closure, intraluminal
shunt, and the placement of tacking sutures at the distal end point. In
this instance, 2 factors emerge that demonstrate a statistically
significant impact on recurrent carotid stenosis. The use of
patch angioplasty closure reduced the overall risk of recurrent carotid
stenosis from 21.2% to 7.1% in the 90% PPV category, from
16.7% to 4.6% in the 95% PPV category, and from 27.4% to 8.2% in
the Doppler technician's best estimate category. The P
value for significance of difference was <0.001. The use of distal
tacking sutures also appeared to have a trend toward reduction of
recurrent carotid stenosis. However, this only reached
statistical significance in the 95% PPV category. It did not have
statistically significant difference in the 90% PPV category or in the
best estimate of stenosis by the Doppler technician. The
use of a shunt had no effect on recurrent stenosis.
View this table:
[in a new window]
Table 5. Probability of Recurrence of
Stenosis and Relative Risk, Comparing Patients With and Without
Selected Characteristics for 2 PPV Scenarios and Estimate of
Stenosis by Doppler Technician
is a Kaplan-Meier
representation of the overall probability of
nonrecurrence of stenosis after surgery at 95% PPV.
This includes all time intervals including residual as well as
recurrent carotid stenosis. Figure 2
is a Kaplan-Meier
representation for the initial time interval within the first
90 days at 95% PPV. This is specific for residual disease. Figure 3
is a Kaplan-Meier curve that examines
the time interval between 90 days and 18 months for the
parameter of recurrent carotid stenosis with 95%
PPV. Figure 4
examines the final time
interval of 18 months to 5 years with respect to the
parameter of recurrent carotid stenosis at 95%
PPV. Figure 5
examines the probability of
nonrecurrence of stenosis after CEA and compares the
outcome of patients undergoing patch angioplasty with those who had CEA
and primary closure. This is the only factor that showed a highly
statistically significant difference in favor of the patch angioplasty,
and that difference is evident in the curve separations.

View larger version (11K):
[in a new window]
Figure 1. Kaplan-Meier curve documents the probability of
nonrecurrence of stenosis after operation at 95% PPV.
This represents both residual and recurrent disease.

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[in a new window]
Figure 2. Kaplan-Meier curve documents the probability of
nonrecurrent stenosis within the first 90 days after operation
at 95% PPV. This represents residual disease.

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[in a new window]
Figure 3. Kaplan-Meier curve documents the probability of
nonrecurrent carotid stenosis in the interval 90 days to 18
months after operation at 95% PPV. This is true recurrence,
probably due to myointimal hyperplasia.

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[in a new window]
Figure 4. Kaplan-Meier curve documents the probability of
nonrecurrent stenosis in the interval between 18 months and 5
years at 95% PPV. This represents the development of a new
lesion, probably atherosclerosis.

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[in a new window]
Figure 5. Kaplan-Meier curve compares the probability of
nonrecurrent stenosis after operation and compares the
incidence in patients in whom the arteriotomy was closed with a patch
angioplasty with the incidence in those undergoing primary
arterial closure. This summarizes the experience in all
time intervals and demonstrates a statistically significant difference
in favor of patch closure.
examines the impact of recurrent
carotid stenosis with respect to subsequent neurological end
points in the form of ipsilateral stroke. Although a higher percentage
of patients with recurrent stenosis experienced a stroke
compared with those without, the P value fails to show a
strong association between recurrent carotid stenosis and
subsequent ipsilateral stroke, possibly because the number of stroke
events is small and the study is potentially statistically underpowered
to demonstrate a clear relationship.
View this table:
[in a new window]
Table 6. Rate of Recurrent Stenosis vs Ipsilateral
Stroke for 2 Doppler Scenarios
![]()
Discussion
Top
Abstract
Introduction
Subjects and Methods
Results
Discussion
References
ACAS has proven that CEA plus best medical management for patients
with stenoses
60% resulted in fewer fatal and nonfatal
strokes than a corresponding group of patients treated with best
medical management alone. There was a 5.9% absolute risk reduction and
a 53% relative risk reduction in favor of
operation.4 The continuing benefit to patients
undergoing CEA will in part be related to the durability of the
operation, as evidenced by the incidence of recurrent carotid
stenosis and whether those patients who suffer
recurrence develop symptoms and the need for further surgical
repair.
![]()
Acknowledgments
This study was supported by the National Institutes of Health
(National Institute of Neurological Disorders and Stroke grant
NS22611).
![]()
Footnotes
Presented at the 23rd International Joint Conference on Stroke and Cerebral Circulation, February 57, 1998, Orlando, Fla.
![]()
References
Top
Abstract
Introduction
Subjects and Methods
Results
Discussion
References
1.
North American Symptomatic
Carotid Endarterectomy Trial Collaborators.
Beneficial effect of carotid endarterectomy in
symptomatic patients with high-grade carotid
stenosis. N Engl J Med. 1991;325:445453.[Abstract]
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