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From the Department of Surgery (T.S.H., T.C.F., J.M.S.), University of
Florida College of Medicine; the Department of Surgery (T.C.F.), Gainesville
Veterans Administration Medical Center; and the Department of Health Policy
and Epidemiology (K.G.W., J.K.C., D.A.D.) of the University of Florida College
of Medicine, Gainesville, Fla; and the Duke University School of Medicine
(K.G.W.), Durham, NC.
Correspondence to Thomas S. Huber, MD, PhD, Section of Vascular Surgery, Department of Surgery, PO Box 100286, University of Florida College of Medicine, Gainesville, FL 32610-0286. E-mail Huber{at}surgery.ufl.edu
Methods—Patients undergoing CEA (ICD-9-CM 38.12) in nonfederal
Florida hospitals were identified from the discharge database. Data
were analyzed by federal fiscal year (FY, October 1 through
September 30), comparing the years following the Advisory (FY95-FY96)
to the preceding 3 years (FY92-FY94).
Results—There was a 68.3% increase in the number of CEAs during
FY95-FY96 (mean FY92-FY94, 7 343; mean FY95-FY96, 12 356). This
exceeded increases in total hospital discharges (4.5%), surgical
discharges (2.2%), and the state's population (4.7%). The increase
in CEAs spanned all patient demographic groups (gender, race, and age),
although the magnitude was not consistent (range, 57.8%
increase for 55 to 64 age group; 92.9% increase for >84 age group).
Concomitantly, there was a significant decrease in mortality (1.2%
versus 0.8%), cardiac complication rate (ICD-9-CM 997.1, 4.1% versus
3.0%) and percentage of patients discharged >7 days postoperatively
(8.9% versus 4.9%). Mean length of stay declined 28% (5.8 versus 4.1
days), and mean adjusted charges declined 7% ($19 456 versus
$18 055). Although the average case was less costly, the increased
volume resulted in an estimated $56 million increase in annual hospital
payments.
Conclusions—The dramatic increase in the number of CEAs performed
in the state of Florida after release of the ACAS Clinical Advisory
suggests a causal relationship and mandates further cost-effectiveness
analyses.
Despite the continuing controversy concerning the results of the ACAS,
it appears that release of these results may have significantly
affected practice patterns. Huber et al14
recently reported a 43.4% increase in the volume of CEAs throughout
the Veterans Affairs Medical Centers during the federal FY (October 1
through September 30) following release of the ACAS Clinical Advisory
(September 28, 1994). This was seen despite a system-wide decrease in
the number of surgical procedures and the number of inpatient
admissions. Furthermore, the increase spanned almost all categories of
health care providers (ie, surgeon type, hospital classification,
geographic region). However, these results cannot be extrapolated
outside Veterans Affairs Medical Centers because the patient
populations and resources are not necessarily comparable. Indeed,
98.6% of the CEAs examined in that study were performed in male
veterans. The current study was designed to retrospectively examine the
effect of the release of the ACAS results on the volume of CEAs
performed in all nonfederal Florida hospitals using the state hospital
discharge database.
A total of 46 741 CEAs were performed in nonfederal Florida hospitals
during the 5 FYs analyzed. The number of CEAs performed during
each FY was expressed as a rate per hospital discharges, per surgical
discharges, and per the state population. The numbers of hospital and
surgical discharges were obtained from the AHCA database; the latter
was based on "surgical" DRGs (HCFA). The estimated state population
was obtained from the Bureau of Economic and Business Research at the
University of Florida and was based on the US Census data. The
incidence of CEA per the state population was calculated for each FY
using population estimates for the corresponding calendar year.
The volume of CEAs was analyzed by demographic group, RMS and
SIS categories, and hospital. The number of CEAs and the population
rate were broken down by age group, gender, and race. The patient
demographics in the AHCA database were obtained by self-report or
observation at the time of hospital admission and were complete in all
abstracts. Patient race was initially classified in the AHCA database
as either "black," "white," or "other," with "black
Hispanic" and "white Hispanic" groups classified as "black"
and "white," respectively. Because of the small number (1% to 2%)
of patients falling in the "other" category and because of the
heterogeneity of this group, the race analysis
was ultimately performed only on those patients classified as
"black" or "white." Similar race classifications were obtained
from the state population database. Patient classification by race was
not available in the discharge abstracts for FY92. The distribution of
CEA cases by RMS and SIS categories was examined for trends in
case-mix.
Mortality and complications were determined from the discharge abstract
using the discharge status, diagnosis codes, and length of stay.
Mortality was defined as in-hospital mortality (discharge status=20).
Postoperative central nervous system and cardiovascular
complications were determined using the ICD-9-CM codes 997.0 to 997.09
(postoperative central nervous system complication) and 997.1
(postoperative cardiac complication), respectively. Postoperative
length of stay >7 days was defined as "long" and used as an
indirect measure of poor outcome.18 Mortality
rates and complication rates were analyzed by year, age,
gender, and race.
The hospital charges (in dollars) for the inpatient admission in which
the patient underwent CEA were obtained from the discharge abstract.
Hospital payments were estimated based on the ratios of charges to
payments for the various payors. The following payment (collection)
rate assumptions were used: Medicare traditional, 70%; Medicare HMO,
67%; Medicaid traditional, 60%; Medicaid HMO, 58%; commercial
traditional, 85%; commercial HMO, 72%; commercial PPO, 80%;
Workers' Compensation, 70%; Champus, 67%; other state/local
government, 45%; Veterans Affairs, 70%;
self-pay/charity/underinsured, 15%; and other, 50%. These rates were
believed to provide a reasonable estimation of payment rates (D.A.D.,
unpublished data, 1998) for inpatient hospital services in Florida
during the study period. Data were not collected on a statewide basis
for items such as professional fees and outpatient services or for
indirect costs, such as lost work time for patients or family care
providers. All charge data were adjusted to FY96 using a 4% annual
rate of inflation.
The rate of CEA, the breakdown of the RMS and SIS groups, and the
mortality and complication rates were compared per year and per
demographic group as appropriate using
The volume of CEAs done after the Clinical Advisory increased for all
age groups (range, 57.8% [increase for age 55 to 64] to 92.9%
[increase for age >84]), for both genders (male, 65.9%; female,
71.6%), and for both races analyzed (white, 62.9%; black,
58.6%) (Table 2
There was a significant decrease in the procedural complication rate
concurrent with the increased number of CEAs done during FY95-FY96
(Table 4
Analysis of the overall data set (FY92-FY96) revealed that CEA
was performed most frequently in men (58.3%), whites (97.9%,
FY93-FY96), and patients between 65 and 74 years (44.7%), although the
rate per 10 000 population was highest in the 75 to 84 age group
(34.1) (Table 5
The temporal relationship between the release of the Clinical Advisory
and the increased procedural volume suggests a casual relationship.
Unfortunately, a more definitive relationship cannot be established
from the database because data on the indications for the CEA (ie,
asymptomatic carotid stenosis,
symptomatic carotid stenosis) were not available.
Interestingly, the volume increase corresponded to release of the
Clinical Advisory rather than publication of the complete study 7
months later (May 10, 1995).5 However, the
Clinical Advisory and the results of the trial both were widely
disseminated throughout the medical and lay literature. The observed
increase is unlikely to be spurious or coincidental in light of the
severe scrutiny applied to CEA historically19 20
and the fact that the increased volume was sustained throughout both
FY95 and FY96. There are other potential explanations for the increase,
including a belated response to the reports of the other
symptomatic and asymptomatic CEA trials.
However, the symptomatic trials1 2 3
were published earlier in the decade and have been well accepted as
reflected by position statements from the American Heart
Association21 and the Society of Vascular
Surgery/International Society for Cardiovascular
Surgery.22 Furthermore, the volume was fairly
constant during the 3 years before the release of the Clinical
Advisory, and the ACAS was the first multicenter prospective trial to
report that CEA reduced the incidence of ipsilateral stroke for
asymptomatic stenosis.
The observed trends for CEA in Florida are consistent with the
43.4% increase of CEAs in Veterans Affairs Medical Centers after
release of the ACAS Clinical Advisory14 and
likely reflect changes in practice patterns throughout the country. The
rate of CEA reported in the current study for FYs 1992 and 1993 are
comparable to those reported for the corresponding calendar years by
Gillum23 using data from the National Hospital
Discharge Survey. Admittedly, there are regional variations in the
utilization of healthcare services.24
Interestingly, Goldstein et al25 reported that
the availability of CEA was the lowest in the South relative to the
Central, Northeast, and West in a national survey of stroke prevention
practices. Thus, it is conceivable that the increase in procedural
volume after ACAS was even greater in the other geographic regions.
The morbidity and mortality rates reported in the study are
consistent with those from multicenter carotid
endarterectomy trials.1 2 3 4 5
This is somewhat surprising in that these figures include results of
every CEA performed in nonfederal hospitals in Florida regardless of
indication, including those performed concomitant with other procedures
(eg, coronary artery bypass grafting). However, these data must
be interpreted with caution and should not be used to draw inference
about the safety of CEA statewide. The AHCA database is an
administrative one that was adapted to answer a specific clinical
question. The abstracts that make up the database include a finite
number of diagnostic and procedural codes and are generated
retrospectively by trained medical coders. The clinical application of
the database is limited by several factors including the inability to
distinguish whether a medical condition (eg, stroke) was preexisting or
a postoperative complication, the accuracy and completeness of the
retrospective coding, and the inability to link the procedural
admission to earlier admissions (complications) that may have been part
of the diagnostic evaluation.26 An
attempt to reduce the former limitation was made by using the ICD-9-CM
code for postoperative central nervous system complication, but even
this is subject to reporting and coding errors. Interestingly, Rothwell
et al27 systematically reviewed all the published
series of CEA performed for symptomatic stenosis
since 1980 and found that the stroke and/or mortality rates varied with
the methods and the authorship of the study, with the highest rates
(7.7%) reported in those studies in which the patients were examined
by a neurologist postoperatively and the lowest rates (2.3%) reported
in studies with a single author affiliated with a department of
surgery. Additionally, the postoperative mortality rate reported here
includes only the deaths that occurred during the admission in which
the CEA was performed rather than the customary 30-day mortality rate.
It is unlikely, however, that the 30-day mortality rate would differ
significantly from these rates because the majority of the
complications and deaths after CEA occur in the immediate postoperative
period, ie, during the same hospital
admission.28
Despite these inherent limitations, several additional features of the
observed mortality and morbidity rates merit further comment. First,
there was a decrease in the mortality and complication rates
concomitant with the increased procedural volume after the Clinical
Advisory. A possible explanation for this observation is an increase in
the number of procedures performed on asymptomatic
patients. This is supported by the observed shift in case-mix to the
lower mortality and lower resource utilization categories, together
with the fact that the mortality and complication rates in ACAS were
lower than those reported from the multicenter symptomatic
trials. Furthermore, a lower complication rate was reported for CEAs
for asymptomatic stenosis in a review of literature
on symptomatic and asymptomatic CEA series that
were performed either by the same surgeon or at the same
institution.29 Interestingly, a comparable
decrease in the mortality and morbidity was not seen in the Veterans
Affairs Medical Centers after release of the Clinical
Advisory.14 Second, the central nervous system
complication rate was significantly higher in women. Admittedly, the
clinical significance of the small difference is uncertain. However,
this observation is consistent with the ACAS trends in which
the risk reduction for CEA was less in women because the
perioperative complication rate was twofold higher. The
authors of the ACAS have commented on these findings, saying there were
too few women in the study and that outcome differences by gender were
not part of the experimental design.11 Third, the
rates of mortality and percentage of patients with postoperative
lengths of stay >7 days were significantly greater in blacks. The
explanation for this observation is not obvious from the data, but may
be related to an increased number of comorbid conditions. Finally,
postoperative length of stay >7 days was used as an indirect marker
for poor outcome after CEA.18 30 Admittedly, the
postoperative length of stay is subject to multiple forces
unrelated to surgical outcome, including economic pressures,
preexisting medical conditions, and social situation that potentially
confound the interpretation of the data. Interestingly, Mitchell et
al31 have reported that physician claims for
postoperative head CT, head MRI, or surgical exploration of the neck
may provide better markers for complications after CEA.
Analysis of the entire data set revealed that there was a
marked disparity in the rate of CEAs between blacks and whites. This
observation is consistent with previous reports from several
national databases including Medicare,32 National
Hospital Discharge Survey,23 and Veterans Affairs
Medical Centers.33 In addition, these
observations parallel the racial disparities reported for other major
cardiovascular procedures.34 35 36
Although these observations suggest a potential racial bias, Horner et
al37 have identified three other plausible
explanations associated with the diagnosis and treatment of
cerebrovascular disease that may explain the disparity: differences in
clinical factors such as location and extent of disease, comorbid
conditions, and operative risk; differences in economic status and the
ability to pay; and differences in patients' decisions to use
diagnostic and therapeutic procedures. Furthermore, Yatsu
et al38 recently identified a genetic variation
among blacks that appears to identify individuals with significant
carotid artery stenosis, and Oddone et
al33 reported that socioeconomic class and access
to care do not completely explain the racial differences in the rates
of cerebral arteriography and CEA in the Veterans Affairs system.
The dramatic increase in the volume of CEAs and the concomitant
significant increase in the estimated hospital payments raise the issue
of whether CEA is cost-effective in patients with
asymptomatic stenoses. The authors of ACAS
concluded that CEA was beneficial for select asymptomatic
patients, but stated that 19 CEAs would be necessary to prevent one
stroke over 5 years. Kuntz and Kent39 developed a
Markov decision analysis model based on the NASCET and ACAS
trials to examine the cost-effectiveness of CEA and reported that it
was cost-effective (cost-effective threshold, $50 000/QALYS) for
symptomatic ($4100/QALYS) but not for
asymptomatic ($52 700/QALYS) lesions. However, CEA for
asymptomatic stenoses became cost-effective in
their model when several of the baseline assumptions were changed (ie,
the risk of untreated patients doubled or the cost of CEA halved).
Cronenwett et al40 used a similar decision
analysis model and reported that CEA was cost-effective
($8000/QALYS) for the typical asymptomatic patient in ACAS;
however, the cost-effectiveness for CEA in asymptomatic
patients was adversely affected by an increase in patient age, an
increase in perioperative stroke rate, and a decrease
in the medical stroke risk. An increase in the patient age (decrease in
life expectancy) had the most dramatic impact in their model, with the
$50 000/QALYS threshold occurring at approximately 75 years of age.
The total number of CEAs performed in patients aged >75 years in the
current study is remarkable in light of this finding. Admittedly, the
specific indications for the procedures in this age group were not
available, but it is likely that a significant proportion, particularly
after the ACAS Advisory, were performed for asymptomatic
stenosis.
In conclusion, the dramatic increase in the number of CEAs performed
throughout the state of Florida after release of the ACAS Clinical
Advisory suggests a causal relationship. The estimated increase in
hospital payments concomitant with the increased volume mandates
further cost-effectiveness analysis, particularly in view of
the limited reported benefit of CEA in asymptomatic
patients.
Received February 5, 1998;
revision received March 26, 1998;
accepted March 26, 1998.
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© 1998 American Heart Association, Inc.
Original Contributions
Effect of the Asymptomatic Carotid Atherosclerosis Study on Carotid Endarterectomy in Florida
Abstract
Top
Abstract
Introduction
Methods
Results
Discussion
References
Background and Purpose—The value of
carotid endarterectomy (CEA) has been defined by
several recent multicenter trials. The clinical effect of these trials
remains undetermined since the Asymptomatic Carotid
Atherosclerosis Study (ACAS) Clinical Advisory (dated
September 28, 1994).
Key Words: carotid arteries • carotid endarterectomy • cerebrovascular disorders • epidemiology • stroke prevention
Introduction
Top
Abstract
Introduction
Methods
Results
Discussion
References
The value of CEA for
both symptomatic and asymptomatic carotid
artery stenoses has been defined by several recent multicenter
trials.1 2 3 4 5 NASCET (1991)1
reported that CEA resulted in a 17% absolute risk reduction for any
ipsilateral stroke compared with best medical management for
stenosis >70%. Similar benefits for symptomatic
stenoses were reported in ECST (1991)2
and VACSG/symptomatic (1991)3 despite
different methodologies, end points, and
formats.6 In contrast, the reported benefit of
CEA for asymptomatic stenoses is less clear.
VACS/asymptomatic (1993)4 reported
that CEA resulted in a 12.6% risk reduction for ipsilateral
neurological events at 4 years for stenosis >50%, but there
was no significant benefit when transient ischemic attacks were
excluded as end points. ACAS (1995)5 reported
that CEA resulted in an estimated 5.9% absolute risk reduction over 5
years for ipsilateral stroke for stenosis >60%, but the
results of the ACAS and the role of CEA for asymptomatic
stenosis have been passionately debated in the
literature.7 8 9 10 11 12 13 ACAS has been criticized on
multiple points, including an overall stoke risk reduction of only 1%
per year, no significant benefit for CEA for preventing disabling
strokes, a minimal benefit of CEA in women, the failure of the degree
of carotid stenosis to correlate with stroke risk, and the use
of noninvasive testing to quantify stenosis.
Methods
Top
Abstract
Introduction
Methods
Results
Discussion
References
Data were obtained from the Florida AHCA database for all
patients undergoing CEA during federal FYs 1992 through 1996 (FY,
October 1 through September 30) using the
ICD-9-CM15 procedure code for CEA, 38.12. All
CEAs performed in Florida were identified regardless of the indication
or whether they were performed concomitant with another procedure. The
AHCA database contains an abstract record for each inpatient
hospitalization for the 202 nonfederal, general, acute-care hospitals
in the state. These records contain up to 10 diagnosis and 10
procedure codes (3 and 2, respectively, for the first quarter of FY92),
along with the DRG, charges, length of stay, source and type of
admission, discharge status, attending physician, surgeon for principal
procedure, and patient demographics (eg, age, race, gender, zip code).
Each discharge was characterized by the RMS and the SIS from 3M Health
Information System's APR-DRG Logic (All Patient Refined DRG Grouper,
Version 12.0 for Multiple Virtual System, 3M Health Information
Services, Wallington, Conn, 1995).16 17 The RMS
and SIS are separate 4-point scales that reflect the risk of
in-hospital mortality and resource demand, respectively (1=least,
4=greatest). The DRGs are a patient classification scheme that provides
a means of relating the type of patients a hospital treats (ie,
case-mix) to the costs incurred by the hospital. There are currently
three major versions of the DRG in use. The basic DRGs are used by the
federal HCFA for hospital payment for Medicare beneficiaries. The
all-patient DRGs are an expansion of the basic DRGs to be more
representative of non-Medicare populations. The
all-patient refined DRGs incorporate into the all-patient DRGs the
complexity (SIS) and risk of mortality (RMS) subclasses based on
complications and comorbidities. 
2
analysis. All data analyses were performed using SAS
Version 6.11 (SAS Institute Inc) running under AIX Version 4.2 on an
IBM RS/6000–59H computer (International Business Machines Co).
Results
Top
Abstract
Introduction
Methods
Results
Discussion
References
There was a 68.3% increase in the total number of CEAs performed
throughout the state of Florida during the two FYs following release of
the ACAS Clinical Advisory compared with the average of the preceding 3
years (Table 1
). The rates of CEA per surgical discharges
(P=0.001), per hospital discharges (P=0.001), and
per the state population (P=0.001) were all significantly
higher during FY95-FY96 than during FY92-FY94, with the magnitude of
the increase ranging from 60.5% to 64.6% (Table 1). The number of
CEAs performed per quarter increased during the first quarter of FY95
(immediately after release of the Clinical Advisory) and was sustained
throughout FY95-FY96 (see the Figure). Analysis of the
procedural volume per hospital demonstrated that there was an increase
in CEAs after ACAS throughout all regions of the state. The mean
increase in the volume of CEAs during FY95-FY96 compared with FY92-FY94
among the 170 hospitals performing at least one CEA during FY92-FY94
was 85.1% (median increase, 57.7%), whereas the mean increase among
the 99 higher volume hospitals (>20 CEAs during FY92) was 72.0%
(median increase, 61.7%).
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Table 1. Total Number and Rate of
CEA
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Figure 1. The quarterly volume of CEAs is shown for FYs 1992 through
1996. The date the ACAS Clinical Advisory was released (September 28,
1994) is indicated by the arrow. ). The magnitude of the increase was consistent
across gender (P=0.07) and race (P=0.71) but was
significantly different among age groups (P=0.001), with the
greatest percentage of increase occurring in the two oldest age groups
(75 to 84 years, 75.8%; >84 years, 92.9%). In addition, there was a
significant shift (P=0.001) in the CEA case-mix after
release of the Clinical Advisory, as reflected by the distribution of
patients among the SIS and RMS (Table 3). The net effect appeared to be
a shift toward the lower classifications for both indices, although the
absolute magnitude of the changes were small.
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Table 2. Number and Rate1
of CEA by Demographic
Group
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Table 3. Breakdown of CEA by Risk of Mortality Scale and
Severity of Illness Scale ). The operative mortality rate decreased from 1.2% to 0.8%
(FY92-FY94 versus FY95-FY96, P=0.001), the mean cardiac
complication rate decreased from 4.1% to 3.0% (P=0.001),
and the percentage of patients with postoperative lengths of stay >7
days decreased from 8.9% to 4.9% (P=0.001). Furthermore,
the mean length of stay declined by 28% (5.8 versus 4.1 days) and the
mean adjusted hospital charges per CEA decreased 7% ($19 456 versus
18 055) after release of the Clinical Advisory. The annual
hospital payments for CEA during FY92-FY94 was $100.3 million, and for
FY95-FY96 it was $156.0 million. Despite a lower cost per case, the
increase in volume of CEA procedures resulted in an estimated $55.7
million yearly increase in hospital payments, exclusive of professional
fees (surgeons, anesthesiologists, radiologists, etc).
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Table 4. Postoperative Mortality and Complication Rates
(%) ). In addition, the central nervous system complication
rate (1.2% versus 0.9%, P=0.003) was significantly higher
in women, but the cardiac complication rate (3.1% versus 3.8%,
P<0.001) was lower. The operative mortality rate (2.0%
versus 0.9%, P<0.001), and the percentage of patients with
postoperative lengths of stay >7 days (12.9% versus 6.8%,
P<0.001) were both significantly greater in blacks, while
the central nervous system complication rate trended toward
significance (1.6% versus 1.0%, P=0.08). Furthermore, the
mortality rate, cardiac complication rate, and percentage of patients
with postoperative lengths of stay >7 days were significantly
different (P<0.001) among the age groups, generally
increasing with age.
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Table 5. Overall (FY92-FY96) CEA Breakdown with Mortality and
Complication Rates by Demographic
Group
Discussion
Top
Abstract
Introduction
Methods
Results
Discussion
References
There was a dramatic, sustained increase in the volume of CEAs
performed in nonfederal hospitals throughout Florida immediately after
release of the ACAS Clinical Advisory on September 28, 1994. The
increase could not be explained by increases in hospital discharges,
surgical discharges, or the state's population. The increased volume
of CEAs was seen throughout all geographic regions of the state and
spanned all patient demographic groups. Concomitantly, there was a
decrease in the procedure-associated in-hospital mortality and
complication rates and a shift in case-mix toward a lower overall
severity.
Selected Abbreviations and Acronyms
ACAS
=
Asymptomatic Carotid Atherosclerosis Study
AHCA
=
Agency for Health Care Administration
CEA
=
carotid endarterectomy
DRG
=
diagnosis related group
ECST
=
European Carotid Surgery Trial
FY
=
fiscal year
HCFA
=
Health Care Financing Administration
HMO
=
Health Maintenance Organization
ICD-9-CM
=
International Classification of Diseases, Ninth Revision,
Clinical Modification
NASCET
=
North American Symptomatic Carotid
Endarterectomy Trial
PPO
=
preferred provider organization
QALYS
=
quality-adjusted life years saved
RMS
=
Risk of Mortality Scale
SIS
=
Severity of Illness Scale
VACSG
=
Veterans Affairs Cooperative Study Group
References
Top
Abstract
Introduction
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;325:445–453.[Abstract]
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