(Stroke. 1997;28:291-296.)
© 1997 American Heart Association, Inc.
Articles |
Asymptomatic Carotid Endarterectomy
Patient and Surgeon Selection
the Department of Surgery (M.J.M., G.G.N., S.A.N.) and the Department of Community Health and Health Studies (J.F.R.), Lehigh Valley Hospital, Allentown, Pa.
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Abstract |
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 Top Abstract IntroductionSubjects and MethodsResultsDiscussionReferences |
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Background and Purpose The applicability of prospective carotid endarterectomy protocols to the general population has been questioned. Outcomes for asymptomatic patients undergoing carotid endarterectomy were compared with the results of the Asymptomatic Carotid Atherosclerosis Study (ACAS) patients treated concurrently at our institution.
Methods Asymptomatic patients undergoing carotid endarterectomies (n=277) from 1987 to 1993 (ACAS enrollment period) were reviewed. Primary end points were mortality, myocardial infarction, and stroke. Five subgroups were studied: (1) ACAS surgical patients; (2) ACAS-eligible patients not enrolled and ACAS surgeons; (3) ACAS-eligible patients not enrolled and non-ACAS surgeons; (4) ACAS-ineligible patients and ACAS surgeons; and (5) ACAS-ineligible patients and non-ACAS surgeons.
Results ACAS-eligible patients were younger (P=.014), had more severe carotid stenosis (P=.001), and had lower incidences of pulmonary (P=.015) and renal (P=.008) diseases compared with ineligible patients. Patient selection (ACAS eligibility) significantly improved outcomes for mortality (P=.014) and myocardial infarction (P=.006). Length of stay favored ACAS-eligible patients (P=.004). ACAS surgeons operated on more severely stenotic carotid lesions (P=.005) and on patients with a lower incidence of coronary artery disease (P=.007). There was no difference in outcomes between ACAS and non-ACAS surgeons.
Conclusions Patient selection was a significant factor in determining outcome. With strict adherence to ACAS enrollment guidelines, the conclusions of ACAS appear applicable to patients seen at our institution with asymptomatic carotid stenosis.
Key Words: carotid endarterectomy • carotid stenosis • treatment outcome
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Introduction |
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TopAbstractIntroductionSubjects and MethodsResultsDiscussionReferences |
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Carotid endarterectomy is a commonly performed vascular surgical procedure in the United States, with approximately 100 000 being performed annually.1 2 The appropriateness of carotid surgery has been examined,3 and guidelines have been developed for selecting patients who should undergo this operation with regard to the degree of their carotid disease, as well as comorbid disease processes.4 5 6 Recent publications have advocated the use of CEA for asymptomatic disease,7 8 9 and ongoing studies are addressing this issue.10 The ACAS concluded that in patients with
60% diameter stenosis of their internal carotid arteries, a combined medical and surgical approach was superior to medical therapy alone when comparing rates of stroke and mortality.7 The stroke/mortality rate was 11.0% for patients in the medical arm of the study compared with 5.1% for patients in the surgical arm of the protocol. However, the applicability of ACAS and other prospective carotid protocols to the general population has been questioned.2 Patient selection has been shown to be of paramount importance.4 11 12 13 14 15 16 17 18 Selection criteria for enrollment in ACAS required patients to be between the ages of 40 and 79 years and exhibit no factors that would produce significant morbidity and mortality within the follow-up period.19 The purpose of this study was to compare the outcomes of asymptomatic patients undergoing CEA with those of ACAS patients treated concurrently at our institution. We also attempted to determine the influence of ACAS eligibility and surgeon selection on outcome.
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Subjects and Methods |
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TopAbstractIntroductionSubjects and MethodsResultsDiscussionReferences |
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The charts of asymptomatic patients undergoing CEA at our community hospital during the ACAS enrollment period were reviewed. Data were collected prospectively from ACAS surgical patients and retrospectively from the medical records of non-ACAS patients. ACAS ineligibility was defined by exclusion criteria established by the Executive Committee for ACAS, including age <40 or >79 years, as well as carotid stenosis <60%. Other criteria were cerebral vascular events in the distribution of the study artery or vertebral basilar symptoms referable to the contralateral cerebral hemisphere and other significant neurological diseases. Patients with cardiovascular conditions, including congestive heart failure, unstable angina, uncontrolled atrial fibrillation, and severe valvular heart disease, were also excluded. Other reasons for exclusion were cancer, uncontrolled diabetes, renal insufficiency, respiratory insufficiency, hepatic disease, and uncontrolled hypertension. In addition, patients who had previous major surgery within 30 days, contraindications to aspirin, or anticoagulation were excluded. Patients with serious complicating conditions that would limit participation or produce disability or death within 5 years and those patients undergoing surgical procedures combined with their CEA were also excluded from the protocol.7 19
Five subgroups were studied: (1) ACAS-protocol surgical patients at our hospital, (2) ACAS-eligible patients but not enrolled in the protocol and operated on by ACAS participating surgeons, (3) ACAS-eligible patients but not enrolled and operated on by non-ACAS participating surgeons, (4) ACAS-ineligible patients operated on by ACAS participating surgeons, and (5) ACAS-ineligible patients operated on by non-ACAS participating surgeons. The ACAS-eligible patients (groups 2 and 3) were excluded from the ACAS protocol because of patient refusal to participate or lack of physician referral to the study physician/investigator.
Data collected consisted of demographics, comorbid diseases, risk factors for atherosclerotic disease, length of stay, and surgeon. Smokers were defined as patients who were currently smoking. Diagnoses of hypertension, cancer, and diabetes were noted from the patient's history, physical examination, and laboratory data. The presence of CAD was based on a history of angina pectoris, a previous MI, congestive heart failure, coronary intervention, or electrocardiographic interpretation of prior or current ischemic events. Chronic obstructive pulmonary disease was defined by history or chest radiograph establishing a diagnosis of chronic obstructive pulmonary disease or emphysema. Renal disease was defined as a serum creatinine level >1.5 mg/dL. Cholesterol values were recorded with respect to levels being greater or less than 200 mg/dL.
The percentage of carotid stenosis was determined from the arteriograms by following the guidelines recommended for ACAS.19 The equation used was (1-MRL/DL)x100, where MRL is the minimal residual lumen (the highest degree of narrowing in the common or internal carotid artery) and DL is the distal lumen in the internal carotid artery that is measured across parallel segments in the most proximal site of no disease.19 The two types of arteriograms used over the study time period were conventional cut films and digital subtraction films using arterial injections. The angiograms of the ACAS-protocol patients (group 1) were read by the study program coordinator and an unbiased radiologist or neurologist. The angiograms of patients in groups 2 through 5 were reviewed by the first author (M.J.M.) using the above methodology without knowledge of the results of prior readings.
A surgeon was considered an ACAS surgeon if he was enrolled in the ACAS protocol during the time when the CEA was performed. There were four ACAS surgeons during the entire study interval. Twelve surgeons were included in the non-ACAS group, but three from this group entered ACAS during the study interval.
Primary end points examined during hospital stay were mortality, MI, and stroke. Stroke was defined as a neurological deficit lasting >24 hours. Stroke findings were recorded with respect to the distribution of flow of the operated artery. MI was defined as findings on electrocardiography as read by a cardiologist or elevated creatine kinase levels with myocardial band fractions >5%. Length of stay and reoperations for postoperative bleeding or question of thrombosis were recorded as secondary end points. Length of stay was determined for the 243 patients undergoing CEA only. For this calculation, the 34 patients who underwent subsequent coronary artery bypass or other major surgery during the same admission were excluded.
Statistical analysis was performed using 
2 or Fisher's exact test for categorical variables. An ANOVA was used for continuous variables.
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Results |
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TopAbstractIntroductionSubjects and MethodsResultsDiscussionReferences |
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Of 1101 CEAs performed from December 1987 through October 1993, 93% were available for review. There were 277 asymptomatic patients included in this study. Eligibility for ACAS was determined for each patient according to the guidelines recommended by the Executive Committee for ACAS.19 There were 158 patients deemed eligible for ACAS and 119 ineligible for the ACAS protocol. Group 1 contained 54 patients, group 2 had 75 patients, group 3 had 29 patients, group 4 had 72 patients, and group 5 had 47 patients. Reasons for exclusion from ACAS were recorded (Table 1
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There were 166 men (59.9%) in the study, and 67 patients (24.2%) used tobacco. CAD was present in 131 patients (47.3%), and 185 patients (66.8%) were hypertensive. Pulmonary disease was diagnosed preoperatively in 26 patients (9.4%), and 20 patients (7.2%) had renal insufficiency. Diabetes mellitus was present in 85 patients (30.7%), and 201 patients (72.6%) had hypercholesterolemia. Sex, tobacco usage, CAD, hypertension, pulmonary disease, renal disease, diabetes mellitus, and hypercholesterolemia were not significantly different among the individual groups.
The groups were then segregated on the basis of ACAS eligibility or the surgeon performing the operative procedure (ACAS participating versus non-ACAS participating), and the data were evaluated for any significant differences (Table 2). The ACAS-protocol patients differed from all the other groups only in that they had a more severe degree of carotid stenosis. The ACAS-eligible patients were younger and had a more severe degree of carotid stenosis than the ineligible patients. They also had lower incidences of pulmonary and renal diseases. The ACAS surgeons operated on more severely stenotic carotid lesions and on patients with a lower incidence of CAD.
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For the 277 procedures, the overall the mortality rate was 1.8% (5 patients), the MI rate was 3.2% (9 patients), and the stroke rate was 1.1% (3 patients). The mortalities occurred after CEA in 3 patients and after carotid surgery with subsequent coronary artery bypass in 2 patients. Of the 9 MIs, 8 were diagnosed immediately after carotid surgery, whereas 1 occurred after CEA and subsequent open heart surgery for valve replacement. All 3 strokes were diagnosed after CEA. Two of the strokes were bilateral, and the other was a contralateral hemispheric stroke to the side of the surgery.
The primary and secondary outcomes are tabulated in Table 3. Overall, when the 223 asymptomatic CEAs performed at our institution outside the ACAS protocol were compared with the 54 CEAs performed at our hospital as part of the ACAS protocol, there was no difference in primary end points. However, ACAS-eligible patients had significantly lower mortality and MI rates than ACAS-ineligible patients. The mortality rate was 0% in groups 1, 2, and 3 (ACAS-eligible patients) compared with 5.6% (4 patients) in group 4 and 2.1% (1 patient) in group 5 (ACAS-ineligible patients). The rate of MI was 0% in groups 1 and 2 and 3.4% (1 patient) in group 3 (ACAS-eligible patients) compared with 8.3% (6 patients) in group 4 and 4.3% (2 patients) in group 5 (ACAS-ineligible patients). The length of stay was the only secondary end point that was statistically significant when comparing the ACAS-eligible groups to the ineligible groups (P<.004). In addition, when comparing groups 1, 2, and 3 (ACAS-eligible patients) to groups 4 and 5 (ACAS-ineligible patients), there was no sex difference (P=.506).
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ACAS surgeons' results for primary and secondary end points did not differ from non-ACAS surgeons' results when the data were analyzed on the basis of status of the surgeon at the time the CEA was performed (Table 3
). Because three surgeons became ACAS surgeons midway through the protocol, the data were also evaluated to determine whether a surgeon's participation in ACAS at any time affected outcomes. The surgeons were assigned to one of two groups defined as never-ACAS surgeons or ACAS surgeons, and their results were compared. Again, there was no difference in outcome regarding the incidence of mortality, MI, stroke, or reoperation. Patients operated on by ACAS surgeons (n=236) had a 1.7% mortality rate (4 patients), 3.0% MI rate (7 patients), and 0.8% stroke rate (2 patients). Patients operated on by never-ACAS surgeons (n=41) had a 2.4% mortality rate (1 patient), a 4.9% MI rate (2 patients), and a 2.4% stroke rate (1 patient).
The clinical characteristics and outcomes were further analyzed by then comparing the individual groups (1 through 5) on the basis of patient eligibility for ACAS and surgeon participation in the ACAS protocol as illustrated for outcomes in Table 4.
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With regard to clinical characteristics, the ACAS-eligible patients operated on by the ACAS surgeons were younger than the ACAS-ineligible patients operated on by the ACAS surgeons (66.5±0.6 years versus 69.5±0.9 years, P=.004), but there was no difference in the age of patients operated on by the non-ACAS surgeons. The ACAS-eligible patients had a higher degree of carotid stenosis compared with the ineligible patients whether operated on by either ACAS surgeons (70.7% versus 63%, P=.001) or non-ACAS surgeons (67.4% versus 58.5%, P=.002). The ACAS-eligible patients operated on by ACAS surgeons had a lower incidence of pulmonary disease compared with their ineligible patients (5.4% versus 15.3%, P=.019), but this difference in patient selection was not seen for the non-ACAS surgeons. The ACAS-eligible patients showed a trend toward a lower incidence of renal disease whether operated on by ACAS surgeons (3.9% versus 12.5%, P=.055) or non-ACAS surgeons (0% versus 12.8%, P=.053).
The incidence of CAD was higher in the ACAS-ineligible patients operated on by non-ACAS surgeons compared with ACAS surgeons (63.8% versus 44.4%, P=.039), but it was not different for ACAS-eligible patients. The clinical characteristics of age, degree of stenosis, and incidences of pulmonary and renal diseases for the ACAS-eligible and -ineligible patients selected for surgery were not affected by participation of the surgeon in ACAS.
ACAS-ineligible patients had higher mortality and MI rates when they were operated on by ACAS surgeons. This difference was not seen for the non-ACAS surgeons (Table 4).
With regard to training, we had surgeons from approved residencies in general vascular surgery (n=2), vascular fellowships (n=6), and cardiothoracic residencies (n=8). There were no differences in outcome in any primary end points between these three groups. Similarly, the volume of cases performed by each surgeon was not related to the outcome with regard to end points. Our data do not allow us to identify any individual, group, or volume of cases that would lead to superior surgical results.
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Discussion |
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TopAbstractIntroductionSubjects and MethodsResultsDiscussionReferences |
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Postoperative morbidity and mortality rates for patients undergoing CEA are being increasingly scrutinized, with emphasis on improved outcomes.20 Patient selection is an important factor in determining outcome from CEA.21 Moore et al4 recommended that only "good risk" asymptomatic patients should undergo CEA. We concur with the recommendations of the American Heart Association that the perioperative stroke/mortality rate for asymptomatic carotid artery surgery should be less than 3%.
Outcomes of symptomatic patients undergoing CEA may be affected by preoperative clinical variables including age, hypertension, and angina pectoris.17 Musser et al16 and Ombrellaro et al14 showed that patients in Goldman classes III and IV have increased risk for adverse cardiac events after CEA.
The conclusions of the ACAS protocol have been closely examined and questioned.2 22 23 24 Statements by the ACAS Executive Committee following publication of the data stressed the importance of patient selection and the use of clinical judgment.25 26
The purpose of this study was to help define the role of patient and surgeon selection on postoperative morbidity and mortality at our institution, as well as to compare outcomes for patients enrolled in ACAS with outcomes in those not enrolled. Patient selection was determined by eligibility for the ACAS protocol, and surgeon selection was by certification to participate in ACAS. Outcomes evaluated were death, MI, and stroke as primary end points and reoperations and length of stay as secondary end points.
Of the clinical characteristics evaluated, the one significant difference between the patients enrolled in ACAS and the 233 patients outside the protocol was the increased severity of carotid stenosis in the ACAS-enrolled group (P<.001). The ACAS-eligible patients (groups 1, 2, and 3) had less comorbid disease and were younger (Table 2). The presence of more advanced age and increased frequency of pulmonary and renal diseases may have contributed to the poorer outcomes noted in the ACAS-ineligible patients. They also had a lesser degree of carotid stenosis. This suggests that the rigorous joint evaluation required by the ACAS protocol selected patients with more advanced carotid disease and fewer comorbid conditions. It also emphasizes the need for careful, conservative patient selection if the ACAS results are to be reproduced in the general population of patients with asymptomatic carotid stenosis.
When the clinical characteristics were segregated on the basis of the surgeon performing the procedure (Table 2), the non-ACAS surgeons selected patients with a lesser degree of carotid stenosis (P=.005) and operated on patients with a higher incidence of CAD (P=.007). This reinforces the value of joint evaluation by medical and surgical specialists in patient selection for this procedure.
With further analysis of clinical characteristics regarding ACAS patient eligibility and surgeon participation in ACAS, it is evident that the ACAS surgeons' eligible patients had fewer comorbid diseases (pulmonary and renal), were younger, and had a greater degree of carotid artery stenosis than their ineligible patients. These selection characteristics most likely contributed to the poorer outcomes for the ineligible patients (Table 4). The non-ACAS surgeons' ineligible patients had a significantly higher incidence of CAD (P=.039). This may be attributed to the fact that 28 of these patients had been selected for carotid surgery before planned coronary artery bypass surgery during the same hospital admission.
In the present study of 277 patients, there was an overall mortality rate of 1.8%, an MI rate of 3.2%, and a stroke rate of 1.1%. This is similar to previously reported data and suggests that in our community hospital, CEA for patients with asymptomatic stenosis can be performed with excellent outcomes similar to those of the ACAS protocol.27 28 29
We found a significant influence of ACAS eligibility on postoperative rates of mortality and MI (Table 3). The mortality and MI rates were both lower in the ACAS-eligible patients. There were no mortalities in the ACAS-eligible patients compared with 5 deaths in the ineligible patients (P=.014). Similarly, the ACAS-eligible patients had only 1 MI (0.6%) compared with the ACAS-ineligible patients who incurred 8 (6.7%, P=.006). This increase in adverse end points for ACAS-ineligible patients emphasizes the necessity for careful patient selection.
The data for each primary end point were also analyzed by combining the individual groups on the basis of ACAS eligibility and surgeon participation in ACAS (Table 4). ACAS surgeons had an increased operative mortality rate when they operated on ACAS-ineligible patients compared with ACAS-eligible patients (5.6% versus 0%, P=.016), but there was no difference for non-ACAS surgeons. In addition, ACAS surgeons had an increased MI rate when they operated on ACAS-ineligible patients compared with ACAS-eligible patients (8.3% versus 0%, P=.002), but again there was no difference for non-ACAS surgeons. Finally, there was no difference in stroke rate for the ACAS-eligible and -ineligible patients whether operated on by ACAS or non-ACAS surgeons. This outcome analysis again confirms the importance of patient selection. The ACAS surgeons' eligible patients had fewer comorbid diseases, were younger, and subsequently had more favorable outcomes with regard to mortality and MI compared with the ineligible patients. In contrast, the non-ACAS surgeons' patients were similar except for one additional comorbid disease in the ineligible patients, but their outcomes were similar for both the eligible and ineligible patients. Neither volume of cases nor surgeon training had any effect on the primary end points of mortality, MI, or stroke. This finding is similar to results reported by Kempczinski et al.30
It appears that at our institution, uniform criteria in patient selection were not used by the physicians, and the outcomes for those patients not meeting the ACAS enrollment criteria were therefore poorer (Table 3). It is now our policy to select asymptomatic patients for CEA only when they meet the guidelines of the ACAS protocol. Patients should be selected for asymptomatic CEA only if they meet the ACAS criteria for lesion stenosis and absence of comorbid diseases that would have excluded them from the original ACAS protocol.
Others have recommended that asymptomatic patients with severe lesions (>75% or 80% reduction diameter stenosis) should undergo surgical repair, since many of these patients will eventually become symptomatic despite the fact that patient selection was not as stringent as that used in the ACAS protocol. If surgery is recommended, the results must yield a stroke/mortality rate <3% to justify surgical intervention. We have no experience with the use of balloon angioplasty-stenting for carotid lesions, and this procedure should be used only as part of prospective protocols until long-term results become available. It is our hope that use of the ACAS guidelines for patient selection will improve outcomes and allow the ACAS conclusions to be valid for all of our patients.
The secondary end point of length of stay was noted to be longer in the ACAS-ineligible patients (Table 3), and since the ineligible patients had more comorbid disease (Table 2), this may have contributed to the longer hospitalization. The rate of reoperation was not statistically significant in any of the comparisons.
The influence of surgeon selection on outcome seems obvious but is controversial.31 Guidelines have been adopted for hospital privileges in vascular surgery.32 Criteria for eligibility to become an ACAS surgeon included a stroke/mortality rate <3% in the prior 50 cases performed, with a minimum of 12 CEAs performed annually.33 In our study, surgeon selection on the basis of ACAS participation did not affect outcomes measured (Tables 3 and 4). This finding may have several possible explanations. Our study design compared data obtained concurrently as part of a carefully structured ACAS research protocol (54 patients) with data collected retrospectively from hospital records (223 patients). It is likely that except for the mortalities, the frequency of MI and stroke was underrecognized in the retrospective group. This would improve the observed results for the patients operated on outside the ACAS protocol. There were 147 procedures by ACAS surgeons, and all the procedures by the non-ACAS surgeons were performed outside the ACAS protocol and evaluated retrospectively. In addition, no attempt was made to determine whether non-ACAS surgeons were eligible to become ACAS surgeons. Three non-ACAS surgeons did become ACAS surgeons midway into the protocol, and their patients were assigned to the group that the surgeon was part of at the time of the operative procedure. Finally, if all the surgeons at our institution had achieved equal expertise, there would be no difference in outcome based on surgeon selection. Data analysis segregating the patients on the basis of ACAS surgeon versus never-ACAS surgeon also showed no difference in primary end points. This suggests uniformity of surgeon expertise.
The percentage of patients who reached end points was low (mortality, 1.8%; MI, 3.2%; and stroke, 1.1%). Due to the sample size, the low percentage of end points reached, and the subanalyses of the data, the power of the statistical analysis may be weakened.
Patient selection for CEA using criteria for ACAS eligibility had a significant impact on the rates of mortality and MI. Deviations from the ACAS eligibility criteria resulted in higher morbidity and mortality. Our data support the use of CEA in asymptomatic patients if the criteria for enrollment in the ACAS protocol are met. Patients not eligible for ACAS had higher morbidity and mortality rates, and the extrapolation of the ACAS recommendations to these patients is not warranted.
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Selected Abbreviations and Acronyms |
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Acknowledgments |
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The authors wish to thank Joan E. Longenecker, RN, BA, for her assistance with data collection.
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Footnotes |
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Reprint requests to Gary G. Nicholas, MD, Department of Surgery, Lehigh Valley Hospital, Cedar Crest and I-78, PO Box 689, Allentown, PA 18105-1556. E-mail gary.nicholas@lvh.com.
Presented in part as a poster at the 1996 Joint Annual Meeting of the North American Chapter of the International Society for Cardiovascular Surgery and the Society for Vascular Surgery, Chicago, Ill, June 9-12, 1996.
Received September 3, 1996; revision received November 7, 1996; accepted November 19, 1996.
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References |
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TopAbstractIntroductionSubjects and MethodsResultsDiscussionReferences |
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Barnett HJM, Eliasziw M, Meldrum HE, Taylor DW. Do the facts and figures warrant a 10-fold increase in the performance of carotid endarterectomy on asymptomatic patients? Neurology. 1996;46:603-608.
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