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Risk factors in a community experience with carotid endarterectomy
Risk factors in a community experience with carotid endarterectomy Drew L. Kirshner, MD, Monica S. O'Brien, MS, R N , and John J. Ricotta, MD,
Rochester, N.Y. Experience with 1035 carotid endarterectomies in a single community over a 2-year period was analyzed. Twenty-two surgeons working in six hospitals were involved. All surgeons had fifll-time or part-time appointments at the University of Rochester, 18 had special interest in vasoalar surgery, and eight had obtained a ce~ificate of qualification in vasoalar surgery. Mortality rate was 1.4% (14 deaths), with additional permanent, nonfatal, neurologic morbidity of 3.4%. Mortality and morbidity were independent of surgeon, caseload, or hospital. Age and prior history of myocardial infarction influenced the incidence of postoperative myocardial infarction but not the incidence of death or neurologic morbidity. Factors that increased the risk of postoperative death or neurologic compfication included hypertension; contralateral carotid disease as manifested by stroke, endarterectomy, or occlusion; whether the patient was a woman; and symptoms of crescendo ischemia. Lack of preoperative neurologic symptoms was correlated with decreased risk of myocardial infarction and neurologic complications. Overall mortality and neurologic morbidity associated with operation for "asymptomatic stenosis" was 3.1% (seven of 222 cases). However, the incidence of contralateral carotid disease was high in the patients in the asymptomatic group (60%), and all complications in this group occurred in patients with prior contralateral carotid endarterectomy or occlusion (p < 0.05). (J VAse StlRG 1989;10:178-86.)
Carotid endarterectomy (CEA) for treatment of patients with cerebrovascular disease has recently come under intense scrutiny. Reports of tmacceptable mortality and morbidity 1-3 and frequent performance of the operation in patients showing no symptoms4 have led to condemnation of the procedure by several prominent authors, s-7There has been strong suggestion that community-wide experience with this procedure is considerably inferior to reports from specialty institutions. A community-wide audit of all CEAs performed over a 2-year period in a moderate-sized metropolitan community was undertaken to address these issues. PATIENTS A N D M E T H O D S In preparation for this audit a code sheet for CEA was developed by the Rochester Vascular Society. This form provided for recording of demographic data, risk factors, indications for operation, angiographic information, morbidity, and mortality. With From the RochesterVascular Society. Supported by a grant from the RochesterArea Foundation. Presented at the Thirty-sixth Scientific Meeting of the North American Chapter, International Society for Cardiovascular Surgery, Chicago, Ill., June 14-15, 1988. Reprint requests: Iohn J. Ricotta, MD, Millard Fillmore Hospitals, 3 Gates Circle, Buffalo,NY 14209. 178
this instrument hospital records of all patients who underwent CEA from Jan. 1, 1984, to Dec. 31, 1985, in the six acute care hospitals of Rochester, N.Y., were reviewed by a physician not involved in the evaluation or treatment of these patients. Operations of carotid subclavian bypass and external CEA were excluded. Office records of the participating surgeons were checked to avoid any inadvertent exclusion of data. In-hospital data were gathered primarily from a thorough review of the hospital records, including angiographic reports and physicians' and nurses' notes. Confidentiality was ensured by providing each physician and hospital with an identification number known only to the physician-reviewer. Data were entered on an IBM PC (IBM Corp., Purchase, N.Y.) and transferred to a VAX 2000 mainframe computer for final statistical analysis. The object of the audit was to record practice patterns, find variations between surgeons, and identify risk factors in the performance of CEA. Analysis of data was done by the Division of Biostatistics at the University of Rochester (C. Cox) by means of chi-square analysis and multiple logistic regression models, as appropriate. In these analyses a stepwise logistic regression analysis was done with a stopping option of approximate statistical significance atp > 0.10. The results are ex-
Volume 10 Number 2 August 1989
Community experiencewith carotid endarterectomy 179
5 (0%) 4-
(3.4°/<
Number of 3. Surgeons 2-
(5.6%) (4%)
113.9%)*
(9.2%)
74.~>/o)(0%)
(2%) (15%11
1-
6
~,
[ I+ ol Io,
~
~
E
,-
"7,
~
~
¢7,
Number of Cases * Includes one surgeon with 16.3% morbidity
Fig. 1. Distribution of caseload by surgeon, with operative neurologic morbidity. Figure depicts the distribution of surgeons (y-axis) by caseload (x-axis) for the 2-year study period. Each surgeon is represented by a single square. Neurologic morbidity by case load is shown in parentheses above each column. There was no statistically significant relationship between number of cases per surgeon and neurologic morbidity. Although morbidity was highest in the 41 to 50 and 71 to 80 case groups, this was the result of only two surgeons' experience and was not statistically different from the rest of the group. pressed as an "odds ratio" for each endpoint. This is the ratio of the odds for endpoint occurrence where the risk factor is present to the odds for endpoint occurrence if the risk factor is absent. For example, an odds ratio of 3.0 means that the odds of a response when the risk factor is present are three times the odds of a response if that risk factor is absent, s Some definition of terms is warranted. Delineation of historic risk factors was straightforward (hypertension, myocardial infarction, prior contralateral endarterectomy, or stroke). Initial symptoms were divided into hemispheric transient ischemic events (including amaurosis fugax), nonhemispheric events as defined by the report of the Joint Committee on the Extracranial Circulation, 9 stroke with functional recovery, deficit with resolution within 30 days, crescendo transient ischemic attacks with no fixed deficit at the time of operation, and stroke in evolution where a deficit was present at the time of surgery. There were three categories of patients showing no symptoms (bruit, stenosis, ulcer) that were not mutually exclusive. In the analysis placement of a patient in any one of these categories was sufficient to classify them as asymptomatic. Type of angiogram and the degree of stenosis (as recorded on the angiography report) were recorded. When the report was un-
available or vague, the angiogram results were reviewed. When measured, severe stenosis was >80% in diameter, whereas moderate stenosis was 50% to 80% in diameter. Postoperative neurologic deficits were classified as transient (<24 hours), resolved (<30 days), or permanent. These determinations were made by review of follow-up office records. Major deficits interfered with employment or daily activities; minor deficits did not. A major neurologic deficit with subsequent death was considered a fatal stroke, Myocardial infarction was documented by changes in the electrocardiographic tracings or cardiac enzymes. Cranial nerve deficits were identified by review of the hospital record.
Surgeon characteristics During this 24-month period, 1035 CEAs were performed in the Rochester community (population base approximately 700,000). Twenty-two surgeons were involved in these cases: one neurosurgeon and 21 general surgeons. Eighteen surgeons were members of the Rochester Vascular Society (Appendix), and eight surgeons had obtained the certificate of qualification in vascular surgery. All surgeons had appointments at the University of Rochester School of Medicine and Dentistry. Caseload varied signifi-
5ournal of VASCULAR SURGERY
180 Kirshner, O'Brien, and Ricotta
Table I. Patient demographics and risk factors (N = 1035) Age Sex Hypertension Myocardial infarction Contralateral stroke Contralateral endarterectomy Ipsflateral stroke Ipsilateral endarterectomy
cantly among surgeons (2 to 261 cases), with a mean caseload of 47 for the 24-month period (Fig. 1). However, only live surgeons treated fewer than 10 patients during this period. Five of the six hospitals were involved in the surgical residency program of the University of Rochester School of Medicine and Dentistry: one parent hospital, and four affiliated hospitals. The remaining hospital did not have house staff. Patient characteristics The demographic characteristics of the patient population and associated risk factors are as follows: hypertension was common in this population (61.6%), and prior myocardial infarction was present in 21.6%. A significant proportion of these patients (almost one fifth Of the patient population) had diffuse extxacranial disease as evidenced by prior contralateral endarterectomy; history of contralateral clinical cerebral infarction was present in 9% of the population (Table I). Findings Indications for surgery and angiographic findings are presented in Tables II and III. Transient ischemia was the most common indication for surgery, followed by lesions ipsilateral to an asymptomatic hemisphere, nonhemispheric symptoms, and stroke with minimal or no residual symptoms. Of the 222 patients with asymptomatic lesions, 215 had moderate to severe stenosis (>50% diameter) determined from angiographic images and noninvasive testing. Angiography was the standard method of evaluating the extracranial circulation and was used in 96.8% of the total group. Intraarterial studies were used ha 678 (65.5%), whereas intravenous digital subtraction angiography alone or in combination with noninvasive testing was used in 321 (31.3%). Endarterectomy was performed without angiography in 36' patients (3.2%). Most patients were operated on for moderate to severe disease. Eighty-three percent of patients had stenoses >50% in diameter, and 50% of
67.8 -+ 8.9 yrs (34-89 yrs) 44.9% F, 55.1% M 638 (61.6%) 223 (21.6%) 95 (9.18%) 194 (18.7%) 175 (16.9) 3
lesions were interpreted as severe (i.e., >80% stenosis). Intraoperative techniques varied with the surgeon involved. Shunts were placed in 257 patients (24.8%). In one hospital selective shunting was used based on monitoring by electroencephalograph, whereas a variety of angiographic and clinical criteria (including stump pressures) were used by surgeons in the other hospitals, and some surgeons placed shunts routinely. Endarterectomies were closed with a patch of vein or prosthetic material in 743 patients (71.8%), and this was a function of surgeon preference. Reoperation was performed in 10 patients who ~uffered bleeding (0.9%), and eight patients (0.8%) underwent reexploration for postoperation carotid occlusion. RESULTS
Morbidity and mortality Perioperative morbidity and mortality are presented in Tables IV and V. Death within 30 days of surgery occurred after 14 operations (1.4%); most deaths occurred after major stroke. Whereas myocardial infarction occurred in 23 patients (2.2%), it was rarely fatal (two cases or 0.2%). In two patients showing no symptoms CEA was performed without: complication; the patients subsequently died after unrelated vascular procedures performed during the same hospitalization. Some perioperativc neurologic morbidity occurred in 69 patients (6.8%). Death or permanent neurologic deficit occurred after CEA in 45 operations (4.4%). Complications were most frequent in patients with crescendo ischemia (7/27 or 25.9%) followed by patients with strokes (13/119 ), and they were lowest in the asymptomatic group of patients (6/222 or 2.6%). Suggestion of a postoperative cranial nerve deficit was noted on review of the charts in 146 cases (14.1%), although most of these problems were transient. The most common deficit was ipsilateral tongue deviation (cranial nerve XII), which occurred
Volume 10 Number2 August 1989
Community experiencewith carotid endarterectomy 181
Table II. Indications for surgery in 1035 patients Transient hemispheric ischemia Reversible neurologic deficit Stroke Nonhemispheric ischemic Asymptomatic* Crescendo ischemiaJTotal
Table III. Angiographic findings Categories* 454 (43.9% 21 (2.0%) 119 (11.5% 192 (18.6% 222 (21.4%) 27 (2.6) 1035 (100%)
Normal Mild without ulcer Mild with ulcer Moderate Severe Occluded Total
7 66 79 331 500 16 999
(0.7%) (6.6%) (7.9%) (33.1%) (50.0%) (1.6%) (96.5%)
*Includes asymptomatic stenosis, ulcer, or bruit. tlncludes 25 crescendo transient ischemic attacks and two crescendo strokes in evolution.
*Generally: mild; <50%; moderate, 50%-79%; severe, 80%99%.
in 92 cases (8.9%) and uniformly resolved before discharge. Facial asymmetry indicating neuropraxia of the marginal mandibular branch of the facial nerve (cranial nerve V) was seen in 37 cases (3.6%). Although this was usually transient, it often persisted for several weeks. Other symptoms that might possibly represent cranial nerve deficits but could be due to other factors were hoarseness (cranial nerve X) in 14 cases and dysphasia (cranial nerve IX) inl three cases. Unfortunately, examination by mirror of the pharynx and larynx was not routinely used in these cases. Such deficits also resolved over a period lasting from days to weeks, whereas short-term problems with cranial nerves were not infrequent, this did not represent a major source of permanent morbidity.
Table IV. Perioperative mortality after CEA (1035 cases)
Influence of surgeon/hospital on patient selection and operative results Although the number of operations performed by each surgeon varied widely in this review, we were unable to document differences between surgeons in terms of case selection or perioperative complicaAons. Nine of the 22 surgeons reported major postoperative neurologic deficits (frequency 0.8% to 5.6%) in their patients. Minor perioperative stroke was reported in the experience of 13 surgeons. The reported frequency of minor deficit after CEA ranged from 2.0% to 6.7%, except that one surgeon reported complications in 43 cases that included six minor deficits (14.0%) and one major deficit (2.3%). During this 2-year period six surgeons performed CEA that produced no neurologic complications. Five of these surgeons performed < 10 CEAs, and the sixth performed 92 CEAs that resulted in no complications (Fig. 1). Since each surgeon concentrated his practice in a single hospital, data on indications, angiographic findings, and neurologic morbidity are presented by hospital in Tables VI and VII. These data show that
No. of cases Percent
Fatal stroke Myocardialinfarction After CABG~ (sameadmission) After AAAt repair (sameadmission) Within 30 days of discharge Total
9 2 1 1 1~' 14
0.9% 0.2% 0.1% 0.1% 0.1% 1.4%
*CABG, coronaryartery bypassgrafting. ?AAA, abdominalaortic aneuysm. indications for surgery were similar throughout the community, and that most patients operated on had >50% diameter reduction documented by angiography. No significant differences were demonstrable between hospitals in any of the parameters described in Tables VI and VII.
Influence of patient characteristics A multiple stepwise logistic regression analysis was used to determine factors that might affect the outcome of CEA. Potential predictors such as age, sex, hypertension, myocardial infarction, initial symptoms, and contralateral carotid disease (marked by prior contralateral stroke, CEA, or occlusion) were tested against outcome. Several outcomes had to be grouped in categories to attain sufficient numbers. Categories included overall mortality; myocardial infarction (fatal and nonfatal); overall neurologic morbidity (fatal, permanent, and transient); major stroke (fatal and nonfatal); and minor deficits (permanent and transient). These data are presented in Table V I I I . Mortality was increased in patients with a history of hypertension, evidence of contralateral carotid disease, and describing symptoms of prior stroke or crescendo ischemia. Postoperative myocardial infarction was more frequent in older patients, women,
Journal of VASCULAR SURGERY
182 Kirshner, O'Brien, and Ricotta
Table V. Perioperative neurologic complications by surgical indication Indications
Fatal stroke (%)
No.
Hemispheric transient isch454 emic attack Reversible neurologic deficit 21 Crecendo ischemia 27 Stroke 119 Nonhemispheric 192 Asymptomatic 222 Total 1035
Nonfatal major stroke Nonfatal minor stroke Resolved deficit (%) (%) <30 D (%)
1 (0.2)
1 (0.2)
15 (3.3)
0 (0.0) 3 (11.1) 3 (2.5) 1 (0.5) 1 (0.6) 9 (0.9)
0 (0.0) 0 (0.0) 1 (0.9) 2 (1.1) 2 (0.8) 6 (0.6)
0 (0.0) 1 (3.7) 4 (3.4) 7 (3.7) 3 (1.4) 30 (2.9)
8 (0.9) 2 3 5 6 O 24
(9.5) (11.1) (4.2) (3.1) (0.0) (2.4)
Total (%)
25 (5.5%) 2 (9.5%) 7 (25.9%) 13 (11.0%) 16 (8.3%) 6 (2.9%) 69 (6.8%)
Table VI. Patient selection and angiographic findings by hospital Hospital Indications
A
B
C
D
Transient ischemic attack 76 (42.5%) 47 (42.0%) 121 (51.5%) 51 (45.5%) 4 (2.2%) 2 (1.8°/6) 7 (3.0%) 4 (3.6%) Reversible neurologic deficit 2 (1.1%) 5 (4.5%) 4 (1.7%) 2 (1.8%) Crescendo ischemia 23 (12.8%) 8 (7.I%) 29 (I2.3%) 7 (6.3%) Stroke 42 (23.5%) 22 (19.6%) 21 (8.9%) 24 (21.4%) Nonhemispheric Asymptomatic 32 (17.9%) 28 (25.0%) 53 (22.6%) 24 (21.4%) 179 112 235 112 Total (1035) Angiographic stenosis >50% 145 (81.0%) 102 (91.1%) 197 (83.8%)
and patients with a prior history of myocardial infarction. Interestingly, hypertension alone was not a risk factor for postoperative myocardial infarction. Patients showing no symptoms had a significantly decreased incidence of myocardial infarction compared to those operated on for symptomatic disease. Some sort of neurologic morbidity was to be expected more frequently in women or those with a history of hypertension, stroke, contralateral disease, or crescendo ischemic events. A history of myocardial infarction did not correlate with occurrence of a postoperative neurologic event unless there was associated preoperative hypertension. The likelihood of postoperative neurologic events was decreased in patients without neurologic symptoms. Major stroke was more frequent in patients with hypertension, contralateral disease, and symptoms of crescendo ischemia. Occurrence of postoperative minor stroke was not influenced by hypertension but was more common in women and in patients with a history of ipsilateral stroke, contralateral disease, or crescendo ischemia. Of all the risk factors, crescendo ischemia, contralateral disease, and hypertension were most predictive of increased morbidity and mortality; whereas lack of neurologic symptoms was a strong predictor of improved outcome.
E
F
21 (42.0%) 138 (39.8%) 1 (2.0%) 3 (0.9%) 1 (2.0%) 13 (3.7%) 5 (10.0%) 47 (13.5%) 13 (26.0%) 70 (20.2%) 9 (18.0%) 76 (21.9%) 50 347
Total and %
454 (43.9%) 21 (2.0%) 27 (2.6%) 119 (11.5%) 192 (18.6%) 222 (21.4%)
97 (86.6%) 46 (92.0%) 274 (79.0%) 861 (83.2%)
Findings in patients with asymptomatic disease The ability of CEA to improve quality of life in patients with asymptomatic carotid disease has come under intense scrutiny in recent years. As a consequence, an in-depth analysis of the asymptomatic population was undertaken. In the 2 years encompassed by this audit, 222 CEAs were performed for "asymptomatic" carotid stenosis. A procedure was classified as asymptomatic if the patient had no known neurologic events related to the ipsilater£" hemisphere and gave no history of nonhemispheric symptoms. Thus patients with contralateral CEA, contralateral stroke, or occlusion were listed as asymptomatic if ipsilateral neurologic symptoms did not precede CEA. In contrast, patients with nonlocalizing symptoms ("drop" attacks, ataxia, uniparesis, cranial nerve dysfunction) were not considered asymptomatic but were assigned to the nonhemispheric category. No distinction was made between patients with no prior history of any cerebrovascular symptoms and those with an asymptomatic cerebral hemisphere. Computerized tomography was not routinely used to evaluate these patients. With few exceptions, CEA was performed in these patients classified as asymptomatic only when severe bifurcation disease was present. Disease was
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Community experience with carotid endarterectomy
183
Table VII. Neurologic mortality/morbidity by hospital
No. of cases Neurologic mortality Nonfatal stroke Temporary neurologic deficit Total
0 10 2 12
A
B
C
D
E
F
179
112
235
112
50
347
(0%) (5.6%) (1.1%) (6.7%)
1 2 4 7
(0.9%) (1.8%) (3.6%) (6.3%)
3 7 6 16
(1.3%) (2.6%) (2.5%) (6.4%)
0 1 2 3
(0%) (0.9%) (1.8%) (2.7%)
0 0 0 0
(0%) (0%) (0%) (0%)
5 16 10 31
(1.1%) (4.6%) (2.2%) (7.7%)
Table VIII. Effect of risk factors on morbidity and mortality by odds ratio All death Age Men Hypertension Prior myocardial in . farction Contralateral disease Asymptomatic Crescendo ischemia
. -7.302 . 5.5022 -23.90 ~ 2
All stroke .
. 0.53 **~ 5.302 .
Major stroke .
. 2.30 ~ 0.26 ~ 6.40 ~ 2
Minor stroke
21/£yocardial infarction
. -4.0022 .
0.42 ~22 --
1.102 0.492 -2.802.
6.10222 0.072~** 5.40 **2
2.00 ~2 0.310*2 4.1022~
-0.33 ~ --
2p < .1; ~ p < .05; ~2~p < .01.
classified as severe (>80% diameter stenosis) in 61% of patients or moderate stcnosis (50% to 80%) in 33% of patients. Twelve patients (5.4%) had mild stenosis (<50%), and in six of these there was angiographic evidence of ulceration. Hypertension was present in 152 patients (68.5%), which was typical of the study population as a whole. Severe or symptomatic contralateral carotid disease was a frequent finding in this group of patients classified as asymptomatic. Twenty-seven patients had angiographic evidence of contralateral internal carotid occlusion, and 65 additional patients showed eidence of severe contralateral stenosis. Thus 92 patients (41%) had anatomic evidence of severe bilateral bifurcation disease. Symptoms of cerebrovascular disease in the contralateral hemisphere were frequent in these patients inthe asymptomatic group. One hundred fifteen patients (52%) had contralateral disease severe enough to warrant CEA or to manifest itself as contralateral cerebral infarction, and 64% had a history of either contralateral stroke, CEA, or occlusion (Table IX). This is of special importance when one remembers that presence of contralateral disease was a significant risk factor for postoperative neurologic deficit. There were three deaths (1.4%) after operation in these 222 patients. One patient died after a major stroke, and two died after a second major cardiovascular procedure (one abdominal aortic aneurysm, one
coronary artery bypass grafting). There were two nonfatal myocardial infarctions (1.8%). Neurologic morbidity occurred in six patients (2.7%) in the asymptomatic group (three major strokes and three minor strokes). Of the six patients who experienced neurologic complications after operation, three had severe ipsilateral stenosis at the time of their asymptomatic CEA, two had evidence of moderate disease, and one had mild disease with ulceration. The frequency of neurologic complications was strikingly related to the presence of severe or symptomatic contralateral disease. All six neurologic complications occurred in patients with evidence of severe contralateral disease. Contralateral CEA had been performed for severe contralateral disease in five patients, and the sixth patient had suffered a contralateral stroke associated with occlusion of the internal carotid artery on that side (Table X). Thus the neurologic complication rate in patients with severe or symptomatic contralateral bifurcation disease was 6 of 138 (4.3%), whereas none of the 92 patients without symptoms or contralateral disease suffered postoperative neurologic complications (Fisher exact test p = 0.047). DISCUSSION Carotid endarterectomy has become the most common peripheral vascular operation performed in the United States and one of the most common of
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Kirshner, O'Brien, and Ricorta
Table IX. Severe or symptomatic contralateral bifurcation in patients classified as asymptomatic (222 patients) ~ Contralateral occlusion
27 patients
Contralateral severe stenosis Contralateral endarterectomy
65 patients 95 patients*
Patients with either contralateral stroke, endarterectomy or occlusion Patients with neither contralateral stroke, endarterectomy or occlusion
18 patients had neither stroke nor endarterectomy on the side of occlusion 13 patients had both contralateral stroke and endarterectomy
134 patients (61%) 88 patients (39%)
*Some categories overlap.
all general surgical operations. As such it has deservedly come under close scrutiny by members of the medical community both in the United States and internationally.17 Currently two multicentered studies are underway to evaluate the efficacy of this procedure. This concern has been heightened by reports of complication rates, which appear to exceed the potential benefit of the operation? -3 Although series from "centers of excellence" have reported acceptably low morbidity and mortality, ~°14 other reports of community-wide practice have suggested that this operation is overused and may be dangerous)-3,s Some authors have suggested that their resuits may be related to hospital sizez3 and that the performance of CEA be prohibited or at least restricted to "centers of excellence" where sufficient volume of procedures are performed to ensure good results; these results are carefully documented) ,s,6,1s This audit was undertaken by the Rochester Vascular Society to address several questions related to the concerns'stated herein: (1) the frequency of CEA in a moderate-sized community, (2) indications for performing the procedure, (3) presence o f demonstrable differences in indications or results within the community and possible relation to caseload or academic affiliation, and (4) particular factors that might influence outcome of carotid surgery. Finally, because of the current controversy surrounding the treatment of patients with asymptomatic disease, special attention was paid to this group of patients. Although the format of this audit (i.e., a retrospective chart review) can be criticized, it does provide easy access to a large number of procedures, and its limitations are minimized when it is focused on events in the hospital. Use of a single physicianreviewer, not involved in the care of these patients, eliminated most physician reporting bias. Complete review of the hospital records, including notes of nurses, house staff, and consultants, was undertaken to identify as many complications as possible. AI-
though it would have been preferable to have each patient examined before and after by a disinterested qualified third party, we feel that the major hard endpoints such as stroke, myocardial infarction, and death should be accurately identified by our review~ The major weakness of this review appears to be in the interpretation ofangiographic data, since in most cases information was gathered from the official radiology report, and the angiogram was not reviewed separately. Although the angiographic categories must be interpreted broadly, they are probably representative of the extent of disease. In the Rochester community most CEAs were performed by surgeons with a special interest in vascular disease. Not all of these physicians had extra training in vascular surgery, although with few exceptions, vascular surgery comprised a significant proportion of their practice, and eight had been awarded the certificate of competence in vascular surgery. Only five surgeons performed fewer than 10 CEAs during the study period, and more than half of the surgeons performed more than 30 such procedures during their 2-year period. All surgeons ha:" full-time or part-time appointments in the university's department of surgery, and all had participated in the teaching of surgical residents. Indications for surgery seemed t~lit accepted national standards, with transient ischemic attacks the most common stimulus to CEA. Asymptomatic stenosis was the indication for surgery in 22% of the cases, which is somewhat less than that reported by others. 4 Some type of contrast angiography was used in 96% of patients. Although one third of patients studied in 1984 and 1985 had an intravenous digital subtraction study, the popularity of this technique has decreased significantly in subsequent years. Most patients had angiographic stenosis of at least moderate or severe degree ipsilateral to the side of operation, and this was particularly true in the asymptomatic group. Thus although a significant n u m b ~
Volume 10 Number 2 August 1989
Community experiencewith carotid endarterectomy 185
Table X. Summary of six patients classified as asymptomatic with neurologic complications
Patient
Complication
Contralateral endarterectomy
1 2 3 4 5 6
Major stroke Minor stroke Minor stroke Minor stroke Resolved deficit Transient ischemic attack
Yes Yes Yes No Yes Yes
Contr alateral stroke
Status of contralateral ~ artery
Status ipsilateral ~ artery
No No No Yes Yes No
Severe Severe Occluded Occluded Severe Severe
Minor with ulcer Moderate Moderate Severe Severe Severe
~Refers to degree of stenosis in the artery at the time it was operated on.
of CEAs were performed in this time period, the indications for surgery do not seem excessively liberal. The audit could not show significant difference between surgeons or hospitals related to indications .:or surgery, use of angiography, morbidity, or mortality. Whereas some variation was found between individuals, the low incidence of complications and small numbers of cases precluded any conclusions of statistical significance. Indeed, it may be impossible to ever prove this point definitively because of the low overall frequency of complications after this procedure. However, it was encouraging to note that only one surgeon reported a neurologic complication rate >10% (16.3%). This surgeon contributed 42 cases (4.1%) to the overall group. The lowest hospital complication rates were in the two hospitals with the fewest procedures. It is impossible to determine whether this was a result of patient selection or a random event. Conclusions must be limited, but these results imply that absolute caseload and hospital or academic affiliation are of secondary importance once a basic familiarity with the management of vas'~ alar disease is demonstrated, a point that has been made by other authors. 4'16 Caseload varied widely (mean: 47 cases over 2 years); only five surgeons performed fewer than 18 CEAs during the 2-year audit period, and only eight performed <12 CEAs per year. A number of factors appear to affect expected outcome after CEA. Some of these, such as hypertension, history of myocardial infarction, and lack of ipsilateral neurologic symptoms, have been noted before. The increased risk of stroke in women is not easily explained, but it might be due to a particular pattern of vascular disease or the size of the internal carotid artery. This required further study, especially in light of the poorer results of antiplatelet agents in this subgroups The finding that advanced age correlated with myocardial infarction but not with death ~r neurologic morbidity confirms prior reports38
The striking effect of contralateral disease on subsequent neurologic complications was of particular interest. Individuals with a history of contralateral CEA, stroke, or occlusion were three times as likely to have a postoperative neurologic event as those with no such evidence of contralateral disease. This was of particular importance in evaluating our asymptomatic group. The overall mortality and neurologic morbidity in the asymptomatic group was 3.5% and was initially quite disturbing. However, further analysis showed that two of three deaths occurred in patients with subsequent vascular surgery. This is a high-risk group and considerable controversy exists about the value of prophylactic CEA in these patients. 19,2° Although mortality might be assigned to the subsequent vascular procedure, we felt this was not appropriate since the prophylactic CEA had failed to achieve its ultimate goal. In addition, 60% of patients classified as asymptomatic had evidence of severe contralateral disease, which has been shown in our overall group to be a predictor of postoperative neurologic complications. Indeed, all the postoperative complications in patients with no symptoms occurred in those with evidence of contralateral disease. It appears that the patient with no symptoms is often one with severe cerebrovascular disease, sometimes more severe than in those patients with symptoms. Our data suggest that different outcomes might be expected in patients classified as asymptomatic based on the severity of their contralateral carotid disease. This is not to say that CEA should not be performed in this group, but the results of this study serve to emphasize the fact that patients with bilateral disease are at increased risk. Green et al.ll noted an increased frequency of electroencephalographic changes at the time of CEA in patients with bilateral disease, and Hertzer et al21,22 have suggested that patients with bilateral disease are at increased risk when monitored without operation. Indeed, our complication rate of 3.5% may be acceptable when
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Kirshner, O'Brien, and Ricotta
prophylactic C E A is performed o n an asymptomatic hemisphere in patients with bilateral carotid disease, but this remains to be proved. O u r data confirm other reports and indicate that C E A can be performed safely by surgeons with a basic familiarity with cerebrovascular disease.~6,23 N o influence o f caseload could be f o u n d o n results alt h o u g h m o s t surgeons performed > 12 cases per year. Mortality and neurologic morbidity are influenced by a n u m b e r o f factors, m o s t especially hypertension and contralateral carotid disease. Future reports o n the o u t c o m e o f patients with carotid disease should take these factors into account. Comparisons o f surgical and nonsurgical therapy m u s t be stratified for these risk factors if meaningful conclusions are to be drawn.
REFERENCES 1. Easton JD, Sherman DG. Stroke and mortality rate in carotid endarterectomy: 228 consecutive operations. Stroke 1977; 8:565-8. 2. Cafferata HT, Gainey MD. Carotid endarterectomy in the community hospital: a continuing controversy. J Cardiovasc Surg (Torino) 1986;4:557-60. 3. BrottT, Thalinger K. The practice of carotid endarterectomy in a large metropolitan area. Stroke 1977;15:950-5. 4. Kempczinski RF, Brott TG, LaBurta RJ. The influence of surgical specialty and caseload on the results of carotid endarterectomy. J VASe SURG 1986;3:911-6. 5. Dyken ML, Pokras R. The performance on endarterectomy for disease of the extracranial arteries of the head. Stroke 1984;15:948-50. 6. Barnett HJM, PlumF, WaltonJN. Carotidendarterectomy-an expression of concern. Stroke 1984; 15:941-3. 7. Kuller LH, Sutton KC. Carotid artery bruit: is it safe and effective to auscultate the neck? Stroke 1984;15:944-7. 8. McCullagh P, Nelder JA. Generalized linear models. London: Chaplin and Hall, 1983. 9. Fields WS, Maslenikov V, Meyer JS, Haas WK, Remington RD, MacDonald M. Joint study of extracranial occlusion. V. Progress report of prognosis following surgery on nonsurgical treatment for transient cerebral ischemic attacks and cervical carotid artery lesions. JAMA 1970;211:1993-2003. 10. Allen GS, Preziosi TJ. Carotid endarterectomy: a prospective
study of its efficacyand safety. Medicine 1981;60:298-309. 11. Green RM, Messick VvT,Ricotta JJ, et al. Benefits, shortcomhags and costs of EEG monitoring. Ann Surg 1985;201:78592. 12. Baker WH, Littooy FN, Hayes AC, et al. Carotid endarterectomy without a shunt: the control series. J VAsc SURG 1984;1:50-8. 13. Thompson JE. Carotid endarterectomy 1982--the state of the art. Br J Surg 1983;70;371-60. 14. Ftde NC, Sun& TM, Robertson JT, Peerless SJ, Shields CB. Multicenter retrospective review of results and complications of carotid endarterectomy ha 1981. Stroke 1986;17:370-6. 15. Luft HS, Bunker JP, Euthoren AC. Should operations be regionalized. The empirical relations betwcen surgical volume and mortality. New Engl J Med 1979;301:1364-9. 16. Hertzer NR, Ave[loneJC, Farrell CJ, et al. The risk of vascular surgery in a metropolitan community. J VAsc SURG 1984; 1:13-21. 17. Canadian cooperative study group: a randomized trial of aspirin and sulfinpyrazone in threatened stroke. New Engl J Med 1978;299:53-9. ,~'-~ 18. Ouriel K, Penn TE, Ricotta JJ, May AG, Green RM, DeWeese JA. Carotid endarterectomy in the elderly patient. Surg Gynecol Obstet 1986;162:334-6. 19. Barnes RW, Nix ML, Sansonetti D, Turley DG, Goldman MR. Late outcomes of untreated asymptomatic carotid disease following cardiovascular operations. J V ~ c SUV,G 1985;2:843-9. 20. Ennix CL Jr, Lawrie GM, Morris GC, et al. Improved restdts of carotid endarterectomy in patients with symptomatic coronary disease: an analysis of 1546 consecutive carotid operations. Stroke 1979;10:122-5.
APPENDIX Members of The Rochester Vascular Society: John Ricotta, MD, James DeWeese, MD, Richard Green, MD, Ethan Welch, MD, Joseph Geary, MD, William Fiore, MD, Robert Caldwell, MD, Carl Andrus, MD, Brendon Brady, MD, Jerry Svoboda, MD, Sadegh Danesh, MD, Robert McCormick, MD, Thomas Penn, MD, Robert R i ~ ers, MD, William Newman, MD, Kenneth Ouriel, MD;' Malur Balaji, MD, Robert George, MD, Tulsi Dass, MD, Theodore Hirokawa, MD, Marvin Lederman, MD, T. K. Oates, MD, John Lyon, MD, Wheelock Southgate, MD, John Porter, MD.
Rochester, N.Y. Experience with 1035 carotid endarterectomies in a single community over a 2-year period was analyzed. Twenty-two surgeons working in six hospitals were involved. All surgeons had fifll-time or part-time appointments at the University of Rochester, 18 had special interest in vasoalar surgery, and eight had obtained a ce~ificate of qualification in vasoalar surgery. Mortality rate was 1.4% (14 deaths), with additional permanent, nonfatal, neurologic morbidity of 3.4%. Mortality and morbidity were independent of surgeon, caseload, or hospital. Age and prior history of myocardial infarction influenced the incidence of postoperative myocardial infarction but not the incidence of death or neurologic morbidity. Factors that increased the risk of postoperative death or neurologic compfication included hypertension; contralateral carotid disease as manifested by stroke, endarterectomy, or occlusion; whether the patient was a woman; and symptoms of crescendo ischemia. Lack of preoperative neurologic symptoms was correlated with decreased risk of myocardial infarction and neurologic complications. Overall mortality and neurologic morbidity associated with operation for "asymptomatic stenosis" was 3.1% (seven of 222 cases). However, the incidence of contralateral carotid disease was high in the patients in the asymptomatic group (60%), and all complications in this group occurred in patients with prior contralateral carotid endarterectomy or occlusion (p < 0.05). (J VAse StlRG 1989;10:178-86.)
Carotid endarterectomy (CEA) for treatment of patients with cerebrovascular disease has recently come under intense scrutiny. Reports of tmacceptable mortality and morbidity 1-3 and frequent performance of the operation in patients showing no symptoms4 have led to condemnation of the procedure by several prominent authors, s-7There has been strong suggestion that community-wide experience with this procedure is considerably inferior to reports from specialty institutions. A community-wide audit of all CEAs performed over a 2-year period in a moderate-sized metropolitan community was undertaken to address these issues. PATIENTS A N D M E T H O D S In preparation for this audit a code sheet for CEA was developed by the Rochester Vascular Society. This form provided for recording of demographic data, risk factors, indications for operation, angiographic information, morbidity, and mortality. With From the RochesterVascular Society. Supported by a grant from the RochesterArea Foundation. Presented at the Thirty-sixth Scientific Meeting of the North American Chapter, International Society for Cardiovascular Surgery, Chicago, Ill., June 14-15, 1988. Reprint requests: Iohn J. Ricotta, MD, Millard Fillmore Hospitals, 3 Gates Circle, Buffalo,NY 14209. 178
this instrument hospital records of all patients who underwent CEA from Jan. 1, 1984, to Dec. 31, 1985, in the six acute care hospitals of Rochester, N.Y., were reviewed by a physician not involved in the evaluation or treatment of these patients. Operations of carotid subclavian bypass and external CEA were excluded. Office records of the participating surgeons were checked to avoid any inadvertent exclusion of data. In-hospital data were gathered primarily from a thorough review of the hospital records, including angiographic reports and physicians' and nurses' notes. Confidentiality was ensured by providing each physician and hospital with an identification number known only to the physician-reviewer. Data were entered on an IBM PC (IBM Corp., Purchase, N.Y.) and transferred to a VAX 2000 mainframe computer for final statistical analysis. The object of the audit was to record practice patterns, find variations between surgeons, and identify risk factors in the performance of CEA. Analysis of data was done by the Division of Biostatistics at the University of Rochester (C. Cox) by means of chi-square analysis and multiple logistic regression models, as appropriate. In these analyses a stepwise logistic regression analysis was done with a stopping option of approximate statistical significance atp > 0.10. The results are ex-
Volume 10 Number 2 August 1989
Community experiencewith carotid endarterectomy 179
5 (0%) 4-
(3.4°/<
Number of 3. Surgeons 2-
(5.6%) (4%)
113.9%)*
(9.2%)
74.~>/o)(0%)
(2%) (15%11
1-
6
~,
[ I+ ol Io,
~
~
E
,-
"7,
~
~
¢7,
Number of Cases * Includes one surgeon with 16.3% morbidity
Fig. 1. Distribution of caseload by surgeon, with operative neurologic morbidity. Figure depicts the distribution of surgeons (y-axis) by caseload (x-axis) for the 2-year study period. Each surgeon is represented by a single square. Neurologic morbidity by case load is shown in parentheses above each column. There was no statistically significant relationship between number of cases per surgeon and neurologic morbidity. Although morbidity was highest in the 41 to 50 and 71 to 80 case groups, this was the result of only two surgeons' experience and was not statistically different from the rest of the group. pressed as an "odds ratio" for each endpoint. This is the ratio of the odds for endpoint occurrence where the risk factor is present to the odds for endpoint occurrence if the risk factor is absent. For example, an odds ratio of 3.0 means that the odds of a response when the risk factor is present are three times the odds of a response if that risk factor is absent, s Some definition of terms is warranted. Delineation of historic risk factors was straightforward (hypertension, myocardial infarction, prior contralateral endarterectomy, or stroke). Initial symptoms were divided into hemispheric transient ischemic events (including amaurosis fugax), nonhemispheric events as defined by the report of the Joint Committee on the Extracranial Circulation, 9 stroke with functional recovery, deficit with resolution within 30 days, crescendo transient ischemic attacks with no fixed deficit at the time of operation, and stroke in evolution where a deficit was present at the time of surgery. There were three categories of patients showing no symptoms (bruit, stenosis, ulcer) that were not mutually exclusive. In the analysis placement of a patient in any one of these categories was sufficient to classify them as asymptomatic. Type of angiogram and the degree of stenosis (as recorded on the angiography report) were recorded. When the report was un-
available or vague, the angiogram results were reviewed. When measured, severe stenosis was >80% in diameter, whereas moderate stenosis was 50% to 80% in diameter. Postoperative neurologic deficits were classified as transient (<24 hours), resolved (<30 days), or permanent. These determinations were made by review of follow-up office records. Major deficits interfered with employment or daily activities; minor deficits did not. A major neurologic deficit with subsequent death was considered a fatal stroke, Myocardial infarction was documented by changes in the electrocardiographic tracings or cardiac enzymes. Cranial nerve deficits were identified by review of the hospital record.
Surgeon characteristics During this 24-month period, 1035 CEAs were performed in the Rochester community (population base approximately 700,000). Twenty-two surgeons were involved in these cases: one neurosurgeon and 21 general surgeons. Eighteen surgeons were members of the Rochester Vascular Society (Appendix), and eight surgeons had obtained the certificate of qualification in vascular surgery. All surgeons had appointments at the University of Rochester School of Medicine and Dentistry. Caseload varied signifi-
5ournal of VASCULAR SURGERY
180 Kirshner, O'Brien, and Ricotta
Table I. Patient demographics and risk factors (N = 1035) Age Sex Hypertension Myocardial infarction Contralateral stroke Contralateral endarterectomy Ipsflateral stroke Ipsilateral endarterectomy
cantly among surgeons (2 to 261 cases), with a mean caseload of 47 for the 24-month period (Fig. 1). However, only live surgeons treated fewer than 10 patients during this period. Five of the six hospitals were involved in the surgical residency program of the University of Rochester School of Medicine and Dentistry: one parent hospital, and four affiliated hospitals. The remaining hospital did not have house staff. Patient characteristics The demographic characteristics of the patient population and associated risk factors are as follows: hypertension was common in this population (61.6%), and prior myocardial infarction was present in 21.6%. A significant proportion of these patients (almost one fifth Of the patient population) had diffuse extxacranial disease as evidenced by prior contralateral endarterectomy; history of contralateral clinical cerebral infarction was present in 9% of the population (Table I). Findings Indications for surgery and angiographic findings are presented in Tables II and III. Transient ischemia was the most common indication for surgery, followed by lesions ipsilateral to an asymptomatic hemisphere, nonhemispheric symptoms, and stroke with minimal or no residual symptoms. Of the 222 patients with asymptomatic lesions, 215 had moderate to severe stenosis (>50% diameter) determined from angiographic images and noninvasive testing. Angiography was the standard method of evaluating the extracranial circulation and was used in 96.8% of the total group. Intraarterial studies were used ha 678 (65.5%), whereas intravenous digital subtraction angiography alone or in combination with noninvasive testing was used in 321 (31.3%). Endarterectomy was performed without angiography in 36' patients (3.2%). Most patients were operated on for moderate to severe disease. Eighty-three percent of patients had stenoses >50% in diameter, and 50% of
67.8 -+ 8.9 yrs (34-89 yrs) 44.9% F, 55.1% M 638 (61.6%) 223 (21.6%) 95 (9.18%) 194 (18.7%) 175 (16.9) 3
lesions were interpreted as severe (i.e., >80% stenosis). Intraoperative techniques varied with the surgeon involved. Shunts were placed in 257 patients (24.8%). In one hospital selective shunting was used based on monitoring by electroencephalograph, whereas a variety of angiographic and clinical criteria (including stump pressures) were used by surgeons in the other hospitals, and some surgeons placed shunts routinely. Endarterectomies were closed with a patch of vein or prosthetic material in 743 patients (71.8%), and this was a function of surgeon preference. Reoperation was performed in 10 patients who ~uffered bleeding (0.9%), and eight patients (0.8%) underwent reexploration for postoperation carotid occlusion. RESULTS
Morbidity and mortality Perioperative morbidity and mortality are presented in Tables IV and V. Death within 30 days of surgery occurred after 14 operations (1.4%); most deaths occurred after major stroke. Whereas myocardial infarction occurred in 23 patients (2.2%), it was rarely fatal (two cases or 0.2%). In two patients showing no symptoms CEA was performed without: complication; the patients subsequently died after unrelated vascular procedures performed during the same hospitalization. Some perioperativc neurologic morbidity occurred in 69 patients (6.8%). Death or permanent neurologic deficit occurred after CEA in 45 operations (4.4%). Complications were most frequent in patients with crescendo ischemia (7/27 or 25.9%) followed by patients with strokes (13/119 ), and they were lowest in the asymptomatic group of patients (6/222 or 2.6%). Suggestion of a postoperative cranial nerve deficit was noted on review of the charts in 146 cases (14.1%), although most of these problems were transient. The most common deficit was ipsilateral tongue deviation (cranial nerve XII), which occurred
Volume 10 Number2 August 1989
Community experiencewith carotid endarterectomy 181
Table II. Indications for surgery in 1035 patients Transient hemispheric ischemia Reversible neurologic deficit Stroke Nonhemispheric ischemic Asymptomatic* Crescendo ischemiaJTotal
Table III. Angiographic findings Categories* 454 (43.9% 21 (2.0%) 119 (11.5% 192 (18.6% 222 (21.4%) 27 (2.6) 1035 (100%)
Normal Mild without ulcer Mild with ulcer Moderate Severe Occluded Total
7 66 79 331 500 16 999
(0.7%) (6.6%) (7.9%) (33.1%) (50.0%) (1.6%) (96.5%)
*Includes asymptomatic stenosis, ulcer, or bruit. tlncludes 25 crescendo transient ischemic attacks and two crescendo strokes in evolution.
*Generally: mild; <50%; moderate, 50%-79%; severe, 80%99%.
in 92 cases (8.9%) and uniformly resolved before discharge. Facial asymmetry indicating neuropraxia of the marginal mandibular branch of the facial nerve (cranial nerve V) was seen in 37 cases (3.6%). Although this was usually transient, it often persisted for several weeks. Other symptoms that might possibly represent cranial nerve deficits but could be due to other factors were hoarseness (cranial nerve X) in 14 cases and dysphasia (cranial nerve IX) inl three cases. Unfortunately, examination by mirror of the pharynx and larynx was not routinely used in these cases. Such deficits also resolved over a period lasting from days to weeks, whereas short-term problems with cranial nerves were not infrequent, this did not represent a major source of permanent morbidity.
Table IV. Perioperative mortality after CEA (1035 cases)
Influence of surgeon/hospital on patient selection and operative results Although the number of operations performed by each surgeon varied widely in this review, we were unable to document differences between surgeons in terms of case selection or perioperative complicaAons. Nine of the 22 surgeons reported major postoperative neurologic deficits (frequency 0.8% to 5.6%) in their patients. Minor perioperative stroke was reported in the experience of 13 surgeons. The reported frequency of minor deficit after CEA ranged from 2.0% to 6.7%, except that one surgeon reported complications in 43 cases that included six minor deficits (14.0%) and one major deficit (2.3%). During this 2-year period six surgeons performed CEA that produced no neurologic complications. Five of these surgeons performed < 10 CEAs, and the sixth performed 92 CEAs that resulted in no complications (Fig. 1). Since each surgeon concentrated his practice in a single hospital, data on indications, angiographic findings, and neurologic morbidity are presented by hospital in Tables VI and VII. These data show that
No. of cases Percent
Fatal stroke Myocardialinfarction After CABG~ (sameadmission) After AAAt repair (sameadmission) Within 30 days of discharge Total
9 2 1 1 1~' 14
0.9% 0.2% 0.1% 0.1% 0.1% 1.4%
*CABG, coronaryartery bypassgrafting. ?AAA, abdominalaortic aneuysm. indications for surgery were similar throughout the community, and that most patients operated on had >50% diameter reduction documented by angiography. No significant differences were demonstrable between hospitals in any of the parameters described in Tables VI and VII.
Influence of patient characteristics A multiple stepwise logistic regression analysis was used to determine factors that might affect the outcome of CEA. Potential predictors such as age, sex, hypertension, myocardial infarction, initial symptoms, and contralateral carotid disease (marked by prior contralateral stroke, CEA, or occlusion) were tested against outcome. Several outcomes had to be grouped in categories to attain sufficient numbers. Categories included overall mortality; myocardial infarction (fatal and nonfatal); overall neurologic morbidity (fatal, permanent, and transient); major stroke (fatal and nonfatal); and minor deficits (permanent and transient). These data are presented in Table V I I I . Mortality was increased in patients with a history of hypertension, evidence of contralateral carotid disease, and describing symptoms of prior stroke or crescendo ischemia. Postoperative myocardial infarction was more frequent in older patients, women,
Journal of VASCULAR SURGERY
182 Kirshner, O'Brien, and Ricotta
Table V. Perioperative neurologic complications by surgical indication Indications
Fatal stroke (%)
No.
Hemispheric transient isch454 emic attack Reversible neurologic deficit 21 Crecendo ischemia 27 Stroke 119 Nonhemispheric 192 Asymptomatic 222 Total 1035
Nonfatal major stroke Nonfatal minor stroke Resolved deficit (%) (%) <30 D (%)
1 (0.2)
1 (0.2)
15 (3.3)
0 (0.0) 3 (11.1) 3 (2.5) 1 (0.5) 1 (0.6) 9 (0.9)
0 (0.0) 0 (0.0) 1 (0.9) 2 (1.1) 2 (0.8) 6 (0.6)
0 (0.0) 1 (3.7) 4 (3.4) 7 (3.7) 3 (1.4) 30 (2.9)
8 (0.9) 2 3 5 6 O 24
(9.5) (11.1) (4.2) (3.1) (0.0) (2.4)
Total (%)
25 (5.5%) 2 (9.5%) 7 (25.9%) 13 (11.0%) 16 (8.3%) 6 (2.9%) 69 (6.8%)
Table VI. Patient selection and angiographic findings by hospital Hospital Indications
A
B
C
D
Transient ischemic attack 76 (42.5%) 47 (42.0%) 121 (51.5%) 51 (45.5%) 4 (2.2%) 2 (1.8°/6) 7 (3.0%) 4 (3.6%) Reversible neurologic deficit 2 (1.1%) 5 (4.5%) 4 (1.7%) 2 (1.8%) Crescendo ischemia 23 (12.8%) 8 (7.I%) 29 (I2.3%) 7 (6.3%) Stroke 42 (23.5%) 22 (19.6%) 21 (8.9%) 24 (21.4%) Nonhemispheric Asymptomatic 32 (17.9%) 28 (25.0%) 53 (22.6%) 24 (21.4%) 179 112 235 112 Total (1035) Angiographic stenosis >50% 145 (81.0%) 102 (91.1%) 197 (83.8%)
and patients with a prior history of myocardial infarction. Interestingly, hypertension alone was not a risk factor for postoperative myocardial infarction. Patients showing no symptoms had a significantly decreased incidence of myocardial infarction compared to those operated on for symptomatic disease. Some sort of neurologic morbidity was to be expected more frequently in women or those with a history of hypertension, stroke, contralateral disease, or crescendo ischemic events. A history of myocardial infarction did not correlate with occurrence of a postoperative neurologic event unless there was associated preoperative hypertension. The likelihood of postoperative neurologic events was decreased in patients without neurologic symptoms. Major stroke was more frequent in patients with hypertension, contralateral disease, and symptoms of crescendo ischemia. Occurrence of postoperative minor stroke was not influenced by hypertension but was more common in women and in patients with a history of ipsilateral stroke, contralateral disease, or crescendo ischemia. Of all the risk factors, crescendo ischemia, contralateral disease, and hypertension were most predictive of increased morbidity and mortality; whereas lack of neurologic symptoms was a strong predictor of improved outcome.
E
F
21 (42.0%) 138 (39.8%) 1 (2.0%) 3 (0.9%) 1 (2.0%) 13 (3.7%) 5 (10.0%) 47 (13.5%) 13 (26.0%) 70 (20.2%) 9 (18.0%) 76 (21.9%) 50 347
Total and %
454 (43.9%) 21 (2.0%) 27 (2.6%) 119 (11.5%) 192 (18.6%) 222 (21.4%)
97 (86.6%) 46 (92.0%) 274 (79.0%) 861 (83.2%)
Findings in patients with asymptomatic disease The ability of CEA to improve quality of life in patients with asymptomatic carotid disease has come under intense scrutiny in recent years. As a consequence, an in-depth analysis of the asymptomatic population was undertaken. In the 2 years encompassed by this audit, 222 CEAs were performed for "asymptomatic" carotid stenosis. A procedure was classified as asymptomatic if the patient had no known neurologic events related to the ipsilater£" hemisphere and gave no history of nonhemispheric symptoms. Thus patients with contralateral CEA, contralateral stroke, or occlusion were listed as asymptomatic if ipsilateral neurologic symptoms did not precede CEA. In contrast, patients with nonlocalizing symptoms ("drop" attacks, ataxia, uniparesis, cranial nerve dysfunction) were not considered asymptomatic but were assigned to the nonhemispheric category. No distinction was made between patients with no prior history of any cerebrovascular symptoms and those with an asymptomatic cerebral hemisphere. Computerized tomography was not routinely used to evaluate these patients. With few exceptions, CEA was performed in these patients classified as asymptomatic only when severe bifurcation disease was present. Disease was
Volume 10 Number 2 August 1989
Community experience with carotid endarterectomy
183
Table VII. Neurologic mortality/morbidity by hospital
No. of cases Neurologic mortality Nonfatal stroke Temporary neurologic deficit Total
0 10 2 12
A
B
C
D
E
F
179
112
235
112
50
347
(0%) (5.6%) (1.1%) (6.7%)
1 2 4 7
(0.9%) (1.8%) (3.6%) (6.3%)
3 7 6 16
(1.3%) (2.6%) (2.5%) (6.4%)
0 1 2 3
(0%) (0.9%) (1.8%) (2.7%)
0 0 0 0
(0%) (0%) (0%) (0%)
5 16 10 31
(1.1%) (4.6%) (2.2%) (7.7%)
Table VIII. Effect of risk factors on morbidity and mortality by odds ratio All death Age Men Hypertension Prior myocardial in . farction Contralateral disease Asymptomatic Crescendo ischemia
. -7.302 . 5.5022 -23.90 ~ 2
All stroke .
. 0.53 **~ 5.302 .
Major stroke .
. 2.30 ~ 0.26 ~ 6.40 ~ 2
Minor stroke
21/£yocardial infarction
. -4.0022 .
0.42 ~22 --
1.102 0.492 -2.802.
6.10222 0.072~** 5.40 **2
2.00 ~2 0.310*2 4.1022~
-0.33 ~ --
2p < .1; ~ p < .05; ~2~p < .01.
classified as severe (>80% diameter stenosis) in 61% of patients or moderate stcnosis (50% to 80%) in 33% of patients. Twelve patients (5.4%) had mild stenosis (<50%), and in six of these there was angiographic evidence of ulceration. Hypertension was present in 152 patients (68.5%), which was typical of the study population as a whole. Severe or symptomatic contralateral carotid disease was a frequent finding in this group of patients classified as asymptomatic. Twenty-seven patients had angiographic evidence of contralateral internal carotid occlusion, and 65 additional patients showed eidence of severe contralateral stenosis. Thus 92 patients (41%) had anatomic evidence of severe bilateral bifurcation disease. Symptoms of cerebrovascular disease in the contralateral hemisphere were frequent in these patients inthe asymptomatic group. One hundred fifteen patients (52%) had contralateral disease severe enough to warrant CEA or to manifest itself as contralateral cerebral infarction, and 64% had a history of either contralateral stroke, CEA, or occlusion (Table IX). This is of special importance when one remembers that presence of contralateral disease was a significant risk factor for postoperative neurologic deficit. There were three deaths (1.4%) after operation in these 222 patients. One patient died after a major stroke, and two died after a second major cardiovascular procedure (one abdominal aortic aneurysm, one
coronary artery bypass grafting). There were two nonfatal myocardial infarctions (1.8%). Neurologic morbidity occurred in six patients (2.7%) in the asymptomatic group (three major strokes and three minor strokes). Of the six patients who experienced neurologic complications after operation, three had severe ipsilateral stenosis at the time of their asymptomatic CEA, two had evidence of moderate disease, and one had mild disease with ulceration. The frequency of neurologic complications was strikingly related to the presence of severe or symptomatic contralateral disease. All six neurologic complications occurred in patients with evidence of severe contralateral disease. Contralateral CEA had been performed for severe contralateral disease in five patients, and the sixth patient had suffered a contralateral stroke associated with occlusion of the internal carotid artery on that side (Table X). Thus the neurologic complication rate in patients with severe or symptomatic contralateral bifurcation disease was 6 of 138 (4.3%), whereas none of the 92 patients without symptoms or contralateral disease suffered postoperative neurologic complications (Fisher exact test p = 0.047). DISCUSSION Carotid endarterectomy has become the most common peripheral vascular operation performed in the United States and one of the most common of
184
journal of VASCULAR SURGERY
Kirshner, O'Brien, and Ricorta
Table IX. Severe or symptomatic contralateral bifurcation in patients classified as asymptomatic (222 patients) ~ Contralateral occlusion
27 patients
Contralateral severe stenosis Contralateral endarterectomy
65 patients 95 patients*
Patients with either contralateral stroke, endarterectomy or occlusion Patients with neither contralateral stroke, endarterectomy or occlusion
18 patients had neither stroke nor endarterectomy on the side of occlusion 13 patients had both contralateral stroke and endarterectomy
134 patients (61%) 88 patients (39%)
*Some categories overlap.
all general surgical operations. As such it has deservedly come under close scrutiny by members of the medical community both in the United States and internationally.17 Currently two multicentered studies are underway to evaluate the efficacy of this procedure. This concern has been heightened by reports of complication rates, which appear to exceed the potential benefit of the operation? -3 Although series from "centers of excellence" have reported acceptably low morbidity and mortality, ~°14 other reports of community-wide practice have suggested that this operation is overused and may be dangerous)-3,s Some authors have suggested that their resuits may be related to hospital sizez3 and that the performance of CEA be prohibited or at least restricted to "centers of excellence" where sufficient volume of procedures are performed to ensure good results; these results are carefully documented) ,s,6,1s This audit was undertaken by the Rochester Vascular Society to address several questions related to the concerns'stated herein: (1) the frequency of CEA in a moderate-sized community, (2) indications for performing the procedure, (3) presence o f demonstrable differences in indications or results within the community and possible relation to caseload or academic affiliation, and (4) particular factors that might influence outcome of carotid surgery. Finally, because of the current controversy surrounding the treatment of patients with asymptomatic disease, special attention was paid to this group of patients. Although the format of this audit (i.e., a retrospective chart review) can be criticized, it does provide easy access to a large number of procedures, and its limitations are minimized when it is focused on events in the hospital. Use of a single physicianreviewer, not involved in the care of these patients, eliminated most physician reporting bias. Complete review of the hospital records, including notes of nurses, house staff, and consultants, was undertaken to identify as many complications as possible. AI-
though it would have been preferable to have each patient examined before and after by a disinterested qualified third party, we feel that the major hard endpoints such as stroke, myocardial infarction, and death should be accurately identified by our review~ The major weakness of this review appears to be in the interpretation ofangiographic data, since in most cases information was gathered from the official radiology report, and the angiogram was not reviewed separately. Although the angiographic categories must be interpreted broadly, they are probably representative of the extent of disease. In the Rochester community most CEAs were performed by surgeons with a special interest in vascular disease. Not all of these physicians had extra training in vascular surgery, although with few exceptions, vascular surgery comprised a significant proportion of their practice, and eight had been awarded the certificate of competence in vascular surgery. Only five surgeons performed fewer than 10 CEAs during the study period, and more than half of the surgeons performed more than 30 such procedures during their 2-year period. All surgeons ha:" full-time or part-time appointments in the university's department of surgery, and all had participated in the teaching of surgical residents. Indications for surgery seemed t~lit accepted national standards, with transient ischemic attacks the most common stimulus to CEA. Asymptomatic stenosis was the indication for surgery in 22% of the cases, which is somewhat less than that reported by others. 4 Some type of contrast angiography was used in 96% of patients. Although one third of patients studied in 1984 and 1985 had an intravenous digital subtraction study, the popularity of this technique has decreased significantly in subsequent years. Most patients had angiographic stenosis of at least moderate or severe degree ipsilateral to the side of operation, and this was particularly true in the asymptomatic group. Thus although a significant n u m b ~
Volume 10 Number 2 August 1989
Community experiencewith carotid endarterectomy 185
Table X. Summary of six patients classified as asymptomatic with neurologic complications
Patient
Complication
Contralateral endarterectomy
1 2 3 4 5 6
Major stroke Minor stroke Minor stroke Minor stroke Resolved deficit Transient ischemic attack
Yes Yes Yes No Yes Yes
Contr alateral stroke
Status of contralateral ~ artery
Status ipsilateral ~ artery
No No No Yes Yes No
Severe Severe Occluded Occluded Severe Severe
Minor with ulcer Moderate Moderate Severe Severe Severe
~Refers to degree of stenosis in the artery at the time it was operated on.
of CEAs were performed in this time period, the indications for surgery do not seem excessively liberal. The audit could not show significant difference between surgeons or hospitals related to indications .:or surgery, use of angiography, morbidity, or mortality. Whereas some variation was found between individuals, the low incidence of complications and small numbers of cases precluded any conclusions of statistical significance. Indeed, it may be impossible to ever prove this point definitively because of the low overall frequency of complications after this procedure. However, it was encouraging to note that only one surgeon reported a neurologic complication rate >10% (16.3%). This surgeon contributed 42 cases (4.1%) to the overall group. The lowest hospital complication rates were in the two hospitals with the fewest procedures. It is impossible to determine whether this was a result of patient selection or a random event. Conclusions must be limited, but these results imply that absolute caseload and hospital or academic affiliation are of secondary importance once a basic familiarity with the management of vas'~ alar disease is demonstrated, a point that has been made by other authors. 4'16 Caseload varied widely (mean: 47 cases over 2 years); only five surgeons performed fewer than 18 CEAs during the 2-year audit period, and only eight performed <12 CEAs per year. A number of factors appear to affect expected outcome after CEA. Some of these, such as hypertension, history of myocardial infarction, and lack of ipsilateral neurologic symptoms, have been noted before. The increased risk of stroke in women is not easily explained, but it might be due to a particular pattern of vascular disease or the size of the internal carotid artery. This required further study, especially in light of the poorer results of antiplatelet agents in this subgroups The finding that advanced age correlated with myocardial infarction but not with death ~r neurologic morbidity confirms prior reports38
The striking effect of contralateral disease on subsequent neurologic complications was of particular interest. Individuals with a history of contralateral CEA, stroke, or occlusion were three times as likely to have a postoperative neurologic event as those with no such evidence of contralateral disease. This was of particular importance in evaluating our asymptomatic group. The overall mortality and neurologic morbidity in the asymptomatic group was 3.5% and was initially quite disturbing. However, further analysis showed that two of three deaths occurred in patients with subsequent vascular surgery. This is a high-risk group and considerable controversy exists about the value of prophylactic CEA in these patients. 19,2° Although mortality might be assigned to the subsequent vascular procedure, we felt this was not appropriate since the prophylactic CEA had failed to achieve its ultimate goal. In addition, 60% of patients classified as asymptomatic had evidence of severe contralateral disease, which has been shown in our overall group to be a predictor of postoperative neurologic complications. Indeed, all the postoperative complications in patients with no symptoms occurred in those with evidence of contralateral disease. It appears that the patient with no symptoms is often one with severe cerebrovascular disease, sometimes more severe than in those patients with symptoms. Our data suggest that different outcomes might be expected in patients classified as asymptomatic based on the severity of their contralateral carotid disease. This is not to say that CEA should not be performed in this group, but the results of this study serve to emphasize the fact that patients with bilateral disease are at increased risk. Green et al.ll noted an increased frequency of electroencephalographic changes at the time of CEA in patients with bilateral disease, and Hertzer et al21,22 have suggested that patients with bilateral disease are at increased risk when monitored without operation. Indeed, our complication rate of 3.5% may be acceptable when
186
Journal of VASCULAR SURGERY
Kirshner, O'Brien, and Ricotta
prophylactic C E A is performed o n an asymptomatic hemisphere in patients with bilateral carotid disease, but this remains to be proved. O u r data confirm other reports and indicate that C E A can be performed safely by surgeons with a basic familiarity with cerebrovascular disease.~6,23 N o influence o f caseload could be f o u n d o n results alt h o u g h m o s t surgeons performed > 12 cases per year. Mortality and neurologic morbidity are influenced by a n u m b e r o f factors, m o s t especially hypertension and contralateral carotid disease. Future reports o n the o u t c o m e o f patients with carotid disease should take these factors into account. Comparisons o f surgical and nonsurgical therapy m u s t be stratified for these risk factors if meaningful conclusions are to be drawn.
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study of its efficacyand safety. Medicine 1981;60:298-309. 11. Green RM, Messick VvT,Ricotta JJ, et al. Benefits, shortcomhags and costs of EEG monitoring. Ann Surg 1985;201:78592. 12. Baker WH, Littooy FN, Hayes AC, et al. Carotid endarterectomy without a shunt: the control series. J VAsc SURG 1984;1:50-8. 13. Thompson JE. Carotid endarterectomy 1982--the state of the art. Br J Surg 1983;70;371-60. 14. Ftde NC, Sun& TM, Robertson JT, Peerless SJ, Shields CB. Multicenter retrospective review of results and complications of carotid endarterectomy ha 1981. Stroke 1986;17:370-6. 15. Luft HS, Bunker JP, Euthoren AC. Should operations be regionalized. The empirical relations betwcen surgical volume and mortality. New Engl J Med 1979;301:1364-9. 16. Hertzer NR, Ave[loneJC, Farrell CJ, et al. The risk of vascular surgery in a metropolitan community. J VAsc SURG 1984; 1:13-21. 17. Canadian cooperative study group: a randomized trial of aspirin and sulfinpyrazone in threatened stroke. New Engl J Med 1978;299:53-9. ,~'-~ 18. Ouriel K, Penn TE, Ricotta JJ, May AG, Green RM, DeWeese JA. Carotid endarterectomy in the elderly patient. Surg Gynecol Obstet 1986;162:334-6. 19. Barnes RW, Nix ML, Sansonetti D, Turley DG, Goldman MR. Late outcomes of untreated asymptomatic carotid disease following cardiovascular operations. J V ~ c SUV,G 1985;2:843-9. 20. Ennix CL Jr, Lawrie GM, Morris GC, et al. Improved restdts of carotid endarterectomy in patients with symptomatic coronary disease: an analysis of 1546 consecutive carotid operations. Stroke 1979;10:122-5.
APPENDIX Members of The Rochester Vascular Society: John Ricotta, MD, James DeWeese, MD, Richard Green, MD, Ethan Welch, MD, Joseph Geary, MD, William Fiore, MD, Robert Caldwell, MD, Carl Andrus, MD, Brendon Brady, MD, Jerry Svoboda, MD, Sadegh Danesh, MD, Robert McCormick, MD, Thomas Penn, MD, Robert R i ~ ers, MD, William Newman, MD, Kenneth Ouriel, MD;' Malur Balaji, MD, Robert George, MD, Tulsi Dass, MD, Theodore Hirokawa, MD, Marvin Lederman, MD, T. K. Oates, MD, John Lyon, MD, Wheelock Southgate, MD, John Porter, MD.