Carotid Endarterectomy for Asymptomatic Carotid Stenosis: a Ten-year Experience with 120 Procedures in a Fellowship Training Program Robert J. Anderson, MD, Robert W. Hobson II, MD, Frank T. Padberg, Jr, MD, Joseph P. Pecoraro, MD, Robert D. DeGroote, MD, Zafar Jamil, MD, Bing C. Lee, MD, Gary B. Breitbart, MD, Charles D. Franco, MD, N e w a r k , N e w Jersey
Performance of carotid endarterectomy for asymptomatic carotid stenosis has been restricted during recent years because of concern of reported complications in as high as 10-15% of patients, as well as limited long-term data on stroke protection. During the last 10 years, we have studied immediate and long-term results of carotid endarterectomy for asymptomatic disease in 120 patients. Operations were performed by a clinical vascular fellow with a staff surgeon in attendance in 113 (94%) cases with the remainder performed by the staff surgeon. Patients' mean age was 66 years; 82% were men. Risk factors included hypertension (56%), smoking (52%), coronary artery disease (32%), diabetes (24%), and hypercholesterolemia (6%). Arteriographic severity of stenoses was 80-99% in 74%, 60-79% in 22%, and 40-59% in 4% of cases. Postoperative complications included two transient neurological events (1.7%). No permanent strokes or deaths occurred. Using the life table method, cumulative stroke rate was 4.5% for ipsilateral events and 7.3% for contralateral events, confirming the high degree of stroke protection afforded by carotid endarterectomy in this population. Since these results were accomplished in a fellowship training program, we regard adequacy of this experience as the most influential factor in accomplishing this record. Surgeons who are unable to achieve comparable results should consider abandonment of the procedure or an extended period of additional train ing. (Ann Vasc Surg 1991 ;5:111-115). KEY WORDS: Carotid endarterectomy; carotid stenosis; vascular fellowship training programs.
The performance of carotid endarterectomy for asymptomatic carotid stenosis remains controver-
sial. This arises from the lack of prospective randomized data to determine the efficacy of best medical therapy versus similar therapy plus carotid endarterectomy. Ongoing studies [1,2] will address this difficult question, but until then reasonable clinical recommendations for the management of asymptomatic carotid stenosis must be formulated. Morbidity and mortality figures should be audited regularly [3] in this group of highly selected patients. We believe the immediate and long-term results of operation are dependent upon the techni-
From the Section of Vascular Sar~,ery, UMDNJ-New Jersey Medical School, Newark, New Jersey. Presented at the Fifteenth Annual Meeting ~f the Peripheral Vascular Surgery Society, June 2, 1990, Los Angeles, CaliJornia. Reprint requests: Robert W. Hobson H, MD, UMDNJNew Jersey Medical School, 185 South Orange Avenue, MSB G-532 Newark, New Jersey 07103-2757.
lll
112
CAROTID E N D A R T E R E C T O M Y FOR A S Y M P T O M A T I C STENOS1S
cal skill of the surgeon and the perioperative management of the patient. Technical perfection in the performance of the operation and adequacy of surgical training are important factors in achieving acceptably low complication rates. Techniques employed and results obtained in a vascular fellowship program will be presented.
MATERIALS AND METHODS From January 1979 to January 1989 512 carotid endarterectomies were performed at our institution. One-hundred twenty patients underwent carotid endarterectomy for asymptomatic disease. All patients denied history of amaurosis fugax, transient ischemic attacks, stroke, or other lateralizing neurological events. None of the patients had symptoms of vertebrobasilar insufficiency or other nonspecific neurologic complaints. All patients were evaluated by a neurologist prior to operation. Preoperative and postoperative noninvasive techniques employed to evaluate these patients included ocular pneumoplethysmography (OPG-Gee*), realtime B-mode ultrasonography, and Doppler spectrum analysis. Prior to 1980, OPG-Gee was used exclusively. The OPG-Gee was considered abnormal if the ophthalmic artery/brachial artery systolic pressure index was < 0.66 or if the difference between ophthalmic artery pressures was -> 5 mmHg. A real-time spectrum analyzer* and 5 mHz continuous-wave Doppler velocimeter (Model D-10~) were used for spectral analysis with the studies interpreted relative to the peak systolic frequency. As previously reported from this laboratory [4], peak frequencies greater than 8 kHz were consistent with a hemodynamically significant stenosis. Frequencies between 5 and 8 kHz were considered significant only if the OPG-Gee was also positive. Real-time B-mode ultrasonography** was performed with a 4 or 8 MHz scanning probe in two longitudinal planes, anterolateral and posterior to the artery, and in a transverse or cross-sectional plane. Images also were interpreted for irregular, thrombogenic, or ulcerative disease. The hemodynamic significance of carotid stenoses were determined by the results of spectrum analysis or OPG-Gee. All patients had biplanar arteriography prior to carotid endarterectomy. Arteriograms were analyzed for percentage of stenosis and surface irregularity using the reporting standards for cerebrovascular disease published by the Ad Hoc Committee of the Society for Vascular Surgery [5]. *Manufactured by Electrodiagnostic Instruments, Burbank, CA. *Manufactured by Angioscan II, Unigon, Inc., Mt. Vernon, NY. '~Medasonics, Mountain View, CA. **Manufactured by Biosound, Bio-Dynamics, Inc., Indianapolis, IN.
ANNALS OF VASCULAR SURGERY
Technical details of carotid endarterectomy were performed meticulously and contributed to the results of this series. First, arterial lines were utilized in all patients for measurement of arterial pressure and control of hypo- or hypertensive changes during induction of anesthesia, throughout the operation, and postoperatively. Second, a careful anatomic dissection of the artery was accomplished with visualization and protection of cranial nerves. Third, a routine shunt was used in all cases with rehearsal of its placement prior to its operative use. Fourth, adequate distal control of the internal carotid artery allowed direct visualization of the endpoint of endarterectomy. This was mandatory and precluded unrecognized intimal flaps which, if present, indicated use of tacking sutures. Finally, the completed endarterectomy surface was freed of smooth muscle fibers or "stringers" to preclude embolization of debris. Irrigation of the endarterectomized artery with heparinized saline assisted with the identification of this material. Although primary closure of the arteriotomy was done in most cases, patch angioplasty has been used increasingly in recent years. The hand-held continuous wave Doppler was used for qualitative assessment of the endarterectomy site. Audible abnormalities or visualized vascular irregularities indicated selective use of operative arteriography. Immediate postoperative neurologic assessment of the patient in the operating room was performed upon completion of the procedure. Control of perioperative blood pressure in an intensive care unit setting was routinely performed. Following carotid endarterectomy, all patients were seen approximately one week after discharge, at three and six months postoperatively, and every six months thereafter. Endpoints in this study were defined as a focal neurologic deficit lasting more than 24 hours (ie, a stroke) or death. On each follow-up visit, all patients were questioned with regard to neurologic symptoms and underwent noninvasive studies. Analysis of hospital records or interviews with family members or with patients' primary physicians were employed in the follow-up of all interval patients deaths.
RESULTS Of the 120 patients undergoing carotid endarterectomy, 98 (82%) were men and 22 (18%) were women. The average age in this series was 65.6 years with a range of 51 to 86 years. There were 112 (93%) Caucasian patients, five (4%) African-American, and three (3%) Hispanic. Risk factors in this patient population are presented in Table I. Arteriographic evaluation of all patients was performed prior to carotid endarterectomy and assessment of percentage of stenosis was 80-99% in 74%, 60-79% in 22%, and 40-59% in 4% of patients. Restenosis was observed in the postoperative pe-
VOLUME 5 N o 2 - 1991
CAROTID E N D A R T E R E C T O M Y FOR A S Y M P T O M A T I C STENOSIS
TABLE I.--Patient risk factors
% WITHOUT
113
IPSILATERAL STROKE
120
No. of patients 67 63 39 29 7
Risk factors Hypertension Smoking Coronary artery disease Diabetes Hypercholesterolemia
Percent 56 53 33 24 6
100
80
120
01 81 7[ 63 58 51 42 37 27 21 [2
8
8
8
7
3
3
3
2
60
40
20
riod which was clinically asymptomatic. These data are reviewed in Figure 1 using life table analysis. No perioperative strokes or deaths were observed. There were, however, two (1.7%) transient neurological events in this series. One occurred four hours after surgery and consisted of a right hemiparesis which resolved over one hour. The other was an episode of amaurosis fugax. The most c o m m o n perioperative complication was cranial nerve injury in six patients of which two were permanent. Both involved the vagus nerve and resulted in hoarseness. Long-term stroke protection in this group of patients was significant as outlined in Figures 2, 3, and 4 which demonstrate ipsilateral, contralateral, and overall stroke rates using life table analysis. Overall survival in this population was 79% at six years postoperatively and is shown in Figure 5.
DISCUSSION The performance of carotid endarterectomy in patients with asymptomatic carotid stenosis is still very controversial and will likely remain so until the prospective randomized series [1,2] are completed. H o w e v e r , carotid endarterectomy can be used effectively for stroke prophylaxis. Data from several clinical series are reviewed in Tables II and Ill in % WITHOUT
RECURRENCE
i
i
i
i
i
i
r
i
i
i
r
r
10
20
30
40
50
60
70
80
90
100
110
120
140
Fig. 2. Ipsilateral stroke rate in asymptomatic patients undergoing carotid endarterectomy using life table analysis.
which the results of surgical therapy versus nonoperative treatment are compared, respectively. Long-term stroke protection has been accomplished in the current series with an ipsilateral cumulative stroke rate of 4.5%, which was comparable to data reported by one group [8]. The advantages of surgical therapy, however, are only realized if the combined operative mortality and stroke rates are minimized (-< 3%) [10]. However, some authors [i 1,12] have reported combined morbidity and mortality of 10.8% to as high as 21.1%. Although the etiology of such high complication rates is uncertain, several factors may contribute to these results. Lack of adequate training in the management of these patients as well as poor patient selection for the operation may have been among the contributing factors. Krupski and associates [13] reported that the results of carotid endarterectomy in a resident training program were comparable to those from fully trained % WITHOUT
~
130
MONTHS
12o[
120
100
--
0
CONTRALATERAL
STROKE
100
L 80
80
07
77
55
t20
01
81
7t
63
58 5L
42
32
22 2t
~2
8
8
8
7
3
3
3
2
~ 48
.
42
t:,O
3[
.
.
.
.
. 60'
28 21
17 o
5
5
5
5
40
2
2
2
I
40
20
20
0
r
i
i
i
i
10
20
30
40
50
i
O0
i
i
i
70
80
90
i
i
i
i
i
100
110
120
130
140
MONTHS
Fig. 1. Recurrent stenosis rate following carotid endarterectomy in asymptomatic patients using life table analysis9
0
_
i
i
i
i
10
20
30
40
_1
50
i
i
i
h
i
I
i
60
70
80
90
100
110
120
/
~
130
140
MONTHS Fig. 3. Contralateral stroke rate in asymptomatic patients undergoing carotid endarterectomy using life table analysis.
A N N A L S OF VASCULAR SURGERY
CAROTID E N D A R T E R E C T O M Y FOR ASYMPTOMA77C STENOSIS
114
% SURVIVAL
% WITHOUT STROKE
120
[2C
100 20
80
ql
81 71 53
58
51
42
37
27
21
[2
8
8
8
7
3
3
3
12o
8C
2
q i
83
72
b4
5 ~ 0 5 3 ~ 43
60
6C
40
4C
20
2s
0
I
r
I
I
I
I
I
I
I
I
10
20
30
40
50
60
70
80
90
100
~
130
0
140
28
23
9
...............................
7
7
12
I
110 120
38
7
I
I
I
I
I
I
I
I
I
I0
20
30
40
50
60
70
80
90
6
3
I 9
100
3
3
2
I
I
r
ll0
120
130
140
MONTHS
MONTHS
Fig, 4. Overall stroke rate in asymptomatic patients undergoing carotid endarterect0my using life table analysis,
Fig, 5. Overall survival in asymptomatic patients undergoing carotid endarterectomy using life table analysis,
private vascular surgeons, underscoring the importance of Surgical training. In reviewing the first phase operative results in the Veteran's Administration (VA) cooperative clinical trial on asymptomatic carotid stenosis, Towne and colleagues [14] reported a combined stroke and death rate of 4.3%, which was derived from teaching services at university-affiliated VA hospitals. Our own results confirm the value of a supervised training program in a series of 120 operations unaccompanied by stroke or death in patients. These results are continued in the form of long-term ipsilateral stroke protection. Furthermore, surgeons having graduated from approved programs have demonstrated an ability to maintain these low complication rates [15]. Continued and frequent performance of the operation is also important in obtaining low perioperative morbidity and
mortality rates. Rubin and coworkers [16], in reviewing results from a metropolitan community, have recently reported a statistically significant decrease in the incidence of stroke after carotid endarterectomy when performed by surgeons whose clinical practice exceeded five carotid endarterectomies per year. Thus, adequacy of training as well as a continued interest and experience in carotid endarterectomy yields superior results.
CONCLUSIONS Carotid endarterectomy performed on patients with asymptomatic carotid stenosis is a safe and effective operation in this clinical series. Analysis of
TABLE II.mlncidence of stroke in patients undergoing carotid endarterectomy for asymptomatic carotid artery stenoses
Investigator
No. of patients
Perioperative stroke (%)
Thompson [6] Hertzer [7] Moneta [8] Caracci [9] Current series
132 95 56 79 120
1.2 3.4 1.8 2.5 0
Operative mortality (%)
Mean follow-up (mo.)
Ipsilateral (%)
55.1 38 24 21 36
--* --* 4 0 4.5
0 1.1 1.8 1.3 0
Contralateral (%) --* --* 16 0 7.3
Total (%) 5.8 8.4 21.8 2.5 11.8
*Data not reported
TABLE IIl.--Incidence of stroke in patients with nonoperative
carotid artery stenoses
Investigator
No, of patients
Thompson [6] Hertzer [7] Moneta [8] Caracci [9]
138 195 73 62
*Not reported
Mean follow-up (mo.) 1week-124months 33 24 21
management of asymptomatic
Ipsilateral
Contralateral
Total
(%) --* --* 19% 18%
(%) --* --* --* --*
(%) 17.4% 12.8% 19% 18%
VOLUME 5 No 2 - 1991
CAROTID ENDARTERECTOMY FOR AS YMPTOMAT1C STENOSIS
our results suggests that low morbidity can be achieved in a vascular fellowship program. This underscores our opinion that technical proficiency with performance of the operative procedure is of major importance. Routine clinical audits of results with carotid endarterectomy are recommended.
REFERENCES I. Veterans Administration Cooperative Study. Role of carotid endarterectomy in asymptomatic carotid stenosis. Stroke 1986;17:534-539. 2. The Asymptomatic Carotid Atherosclerosis Study Group. Study design for randomized prospective trial of carotid endarterectomy for asymptomatic atherosclerosis. Stroke 1989 ;20: 844-849. 3. HOBSON RW II, TOWNE J. Carotid endarterectomy for asymptomatic carotid stenosis. Stroke 1989;20:575-576. 4. DE GROOTE RD, LYNCH TG, JAMIL Z, et al. Carotid restenosis: long-term noninvasive follow-up after carotid endarterectomy. Stroke 1987;18:1031-1036. 5. Subcommittee on Reporting Standards for Cerebrovascular Disease, Ad Hoc Committee on Reporting Standards. Society for Vascular Surgery/North American Chapter, International Society for Cardiovascular Surgery. Suggested standards for reports dealing with cerebrovascular disease. J Vasc Surg 1988;8:721-729. 6. THOMPSON JE, PATMAN RD, TALKINGTON CM. Asymptomatic carotid bruit: long-term outcome of patients having endarterectomy compared with unoperated controls. Ann Surg 1978,188:308-316.
m m m
115
7. HERTZER NR, FLANAGAN RA Jr, O'HARA PJ, et al. Surgical versus nonoperative treatment of asymptomatic carotid stenosis. Ann Surg 1986;204:163-171. 8. MONETA GL, TAYLOR DC, NICHOLLS SC, et al. Operative versus nonoperative management of asymptomatic high grade internal carotid artery stenosis: improved results with endarterectomy. Stroke 1987;18:1005-1010. 9. CARACCI BF, ZUKOWSKI AJ, HURLEY JJ, et al. Asymptomatic severe carotid stenosis. J Vasc Surg 1989;9: 361-366. 10. CALLOW AD, CAPLAN LR, CORRELL JW, et al. Carotid endarterectomy: what is the current status? Am J Med 1988:85:835-838. 11. BROTT T, THALINGER K. The practice of carotid endarterectomy in a large metropolitan area. Stroke 1984;15:950955. 12. EASTON JD, SHERMAN DG. Stroke and mortality rate in carotid endarterectomy: 228 consecutive operations. Stroke 1977:8: 565-568. 13. KRUPSKI WC, EFFENEY DJ, GOLDSTONE J, et al. Carotid endarterectomy in a metropolitan community: comparison of results from three institutions. Surgery 1985;98: 492499. 14. TOWNE JB, WEISS DG, HOBSON RW If. First phase report of Cooperative Veterans Administration asymptomatic carotid stenosis study--operative morbidity and mortality. J Vase Surg 1990;1l:252-259. 15. BAKER WH, LITTOOY FN, GREISLER HP, et al. Carotid endarterectomy in private practice by fellowship-trained surgeons. Letter to the Editor. Stroke 1987;18:957958. 16. RUBIN JR, PITLUK HC, KING TA, et al. Carotid endarterectomy in a metropolitan community: the early results after 8,535 operations, d Vasc Surg 1988;7:256-260.
Performance of carotid endarterectomy for asymptomatic carotid stenosis has been restricted during recent years because of concern of reported complications in as high as 10-15% of patients, as well as limited long-term data on stroke protection. During the last 10 years, we have studied immediate and long-term results of carotid endarterectomy for asymptomatic disease in 120 patients. Operations were performed by a clinical vascular fellow with a staff surgeon in attendance in 113 (94%) cases with the remainder performed by the staff surgeon. Patients' mean age was 66 years; 82% were men. Risk factors included hypertension (56%), smoking (52%), coronary artery disease (32%), diabetes (24%), and hypercholesterolemia (6%). Arteriographic severity of stenoses was 80-99% in 74%, 60-79% in 22%, and 40-59% in 4% of cases. Postoperative complications included two transient neurological events (1.7%). No permanent strokes or deaths occurred. Using the life table method, cumulative stroke rate was 4.5% for ipsilateral events and 7.3% for contralateral events, confirming the high degree of stroke protection afforded by carotid endarterectomy in this population. Since these results were accomplished in a fellowship training program, we regard adequacy of this experience as the most influential factor in accomplishing this record. Surgeons who are unable to achieve comparable results should consider abandonment of the procedure or an extended period of additional train ing. (Ann Vasc Surg 1991 ;5:111-115). KEY WORDS: Carotid endarterectomy; carotid stenosis; vascular fellowship training programs.
The performance of carotid endarterectomy for asymptomatic carotid stenosis remains controver-
sial. This arises from the lack of prospective randomized data to determine the efficacy of best medical therapy versus similar therapy plus carotid endarterectomy. Ongoing studies [1,2] will address this difficult question, but until then reasonable clinical recommendations for the management of asymptomatic carotid stenosis must be formulated. Morbidity and mortality figures should be audited regularly [3] in this group of highly selected patients. We believe the immediate and long-term results of operation are dependent upon the techni-
From the Section of Vascular Sar~,ery, UMDNJ-New Jersey Medical School, Newark, New Jersey. Presented at the Fifteenth Annual Meeting ~f the Peripheral Vascular Surgery Society, June 2, 1990, Los Angeles, CaliJornia. Reprint requests: Robert W. Hobson H, MD, UMDNJNew Jersey Medical School, 185 South Orange Avenue, MSB G-532 Newark, New Jersey 07103-2757.
lll
112
CAROTID E N D A R T E R E C T O M Y FOR A S Y M P T O M A T I C STENOS1S
cal skill of the surgeon and the perioperative management of the patient. Technical perfection in the performance of the operation and adequacy of surgical training are important factors in achieving acceptably low complication rates. Techniques employed and results obtained in a vascular fellowship program will be presented.
MATERIALS AND METHODS From January 1979 to January 1989 512 carotid endarterectomies were performed at our institution. One-hundred twenty patients underwent carotid endarterectomy for asymptomatic disease. All patients denied history of amaurosis fugax, transient ischemic attacks, stroke, or other lateralizing neurological events. None of the patients had symptoms of vertebrobasilar insufficiency or other nonspecific neurologic complaints. All patients were evaluated by a neurologist prior to operation. Preoperative and postoperative noninvasive techniques employed to evaluate these patients included ocular pneumoplethysmography (OPG-Gee*), realtime B-mode ultrasonography, and Doppler spectrum analysis. Prior to 1980, OPG-Gee was used exclusively. The OPG-Gee was considered abnormal if the ophthalmic artery/brachial artery systolic pressure index was < 0.66 or if the difference between ophthalmic artery pressures was -> 5 mmHg. A real-time spectrum analyzer* and 5 mHz continuous-wave Doppler velocimeter (Model D-10~) were used for spectral analysis with the studies interpreted relative to the peak systolic frequency. As previously reported from this laboratory [4], peak frequencies greater than 8 kHz were consistent with a hemodynamically significant stenosis. Frequencies between 5 and 8 kHz were considered significant only if the OPG-Gee was also positive. Real-time B-mode ultrasonography** was performed with a 4 or 8 MHz scanning probe in two longitudinal planes, anterolateral and posterior to the artery, and in a transverse or cross-sectional plane. Images also were interpreted for irregular, thrombogenic, or ulcerative disease. The hemodynamic significance of carotid stenoses were determined by the results of spectrum analysis or OPG-Gee. All patients had biplanar arteriography prior to carotid endarterectomy. Arteriograms were analyzed for percentage of stenosis and surface irregularity using the reporting standards for cerebrovascular disease published by the Ad Hoc Committee of the Society for Vascular Surgery [5]. *Manufactured by Electrodiagnostic Instruments, Burbank, CA. *Manufactured by Angioscan II, Unigon, Inc., Mt. Vernon, NY. '~Medasonics, Mountain View, CA. **Manufactured by Biosound, Bio-Dynamics, Inc., Indianapolis, IN.
ANNALS OF VASCULAR SURGERY
Technical details of carotid endarterectomy were performed meticulously and contributed to the results of this series. First, arterial lines were utilized in all patients for measurement of arterial pressure and control of hypo- or hypertensive changes during induction of anesthesia, throughout the operation, and postoperatively. Second, a careful anatomic dissection of the artery was accomplished with visualization and protection of cranial nerves. Third, a routine shunt was used in all cases with rehearsal of its placement prior to its operative use. Fourth, adequate distal control of the internal carotid artery allowed direct visualization of the endpoint of endarterectomy. This was mandatory and precluded unrecognized intimal flaps which, if present, indicated use of tacking sutures. Finally, the completed endarterectomy surface was freed of smooth muscle fibers or "stringers" to preclude embolization of debris. Irrigation of the endarterectomized artery with heparinized saline assisted with the identification of this material. Although primary closure of the arteriotomy was done in most cases, patch angioplasty has been used increasingly in recent years. The hand-held continuous wave Doppler was used for qualitative assessment of the endarterectomy site. Audible abnormalities or visualized vascular irregularities indicated selective use of operative arteriography. Immediate postoperative neurologic assessment of the patient in the operating room was performed upon completion of the procedure. Control of perioperative blood pressure in an intensive care unit setting was routinely performed. Following carotid endarterectomy, all patients were seen approximately one week after discharge, at three and six months postoperatively, and every six months thereafter. Endpoints in this study were defined as a focal neurologic deficit lasting more than 24 hours (ie, a stroke) or death. On each follow-up visit, all patients were questioned with regard to neurologic symptoms and underwent noninvasive studies. Analysis of hospital records or interviews with family members or with patients' primary physicians were employed in the follow-up of all interval patients deaths.
RESULTS Of the 120 patients undergoing carotid endarterectomy, 98 (82%) were men and 22 (18%) were women. The average age in this series was 65.6 years with a range of 51 to 86 years. There were 112 (93%) Caucasian patients, five (4%) African-American, and three (3%) Hispanic. Risk factors in this patient population are presented in Table I. Arteriographic evaluation of all patients was performed prior to carotid endarterectomy and assessment of percentage of stenosis was 80-99% in 74%, 60-79% in 22%, and 40-59% in 4% of patients. Restenosis was observed in the postoperative pe-
VOLUME 5 N o 2 - 1991
CAROTID E N D A R T E R E C T O M Y FOR A S Y M P T O M A T I C STENOSIS
TABLE I.--Patient risk factors
% WITHOUT
113
IPSILATERAL STROKE
120
No. of patients 67 63 39 29 7
Risk factors Hypertension Smoking Coronary artery disease Diabetes Hypercholesterolemia
Percent 56 53 33 24 6
100
80
120
01 81 7[ 63 58 51 42 37 27 21 [2
8
8
8
7
3
3
3
2
60
40
20
riod which was clinically asymptomatic. These data are reviewed in Figure 1 using life table analysis. No perioperative strokes or deaths were observed. There were, however, two (1.7%) transient neurological events in this series. One occurred four hours after surgery and consisted of a right hemiparesis which resolved over one hour. The other was an episode of amaurosis fugax. The most c o m m o n perioperative complication was cranial nerve injury in six patients of which two were permanent. Both involved the vagus nerve and resulted in hoarseness. Long-term stroke protection in this group of patients was significant as outlined in Figures 2, 3, and 4 which demonstrate ipsilateral, contralateral, and overall stroke rates using life table analysis. Overall survival in this population was 79% at six years postoperatively and is shown in Figure 5.
DISCUSSION The performance of carotid endarterectomy in patients with asymptomatic carotid stenosis is still very controversial and will likely remain so until the prospective randomized series [1,2] are completed. H o w e v e r , carotid endarterectomy can be used effectively for stroke prophylaxis. Data from several clinical series are reviewed in Tables II and Ill in % WITHOUT
RECURRENCE
i
i
i
i
i
i
r
i
i
i
r
r
10
20
30
40
50
60
70
80
90
100
110
120
140
Fig. 2. Ipsilateral stroke rate in asymptomatic patients undergoing carotid endarterectomy using life table analysis.
which the results of surgical therapy versus nonoperative treatment are compared, respectively. Long-term stroke protection has been accomplished in the current series with an ipsilateral cumulative stroke rate of 4.5%, which was comparable to data reported by one group [8]. The advantages of surgical therapy, however, are only realized if the combined operative mortality and stroke rates are minimized (-< 3%) [10]. However, some authors [i 1,12] have reported combined morbidity and mortality of 10.8% to as high as 21.1%. Although the etiology of such high complication rates is uncertain, several factors may contribute to these results. Lack of adequate training in the management of these patients as well as poor patient selection for the operation may have been among the contributing factors. Krupski and associates [13] reported that the results of carotid endarterectomy in a resident training program were comparable to those from fully trained % WITHOUT
~
130
MONTHS
12o[
120
100
--
0
CONTRALATERAL
STROKE
100
L 80
80
07
77
55
t20
01
81
7t
63
58 5L
42
32
22 2t
~2
8
8
8
7
3
3
3
2
~ 48
.
42
t:,O
3[
.
.
.
.
. 60'
28 21
17 o
5
5
5
5
40
2
2
2
I
40
20
20
0
r
i
i
i
i
10
20
30
40
50
i
O0
i
i
i
70
80
90
i
i
i
i
i
100
110
120
130
140
MONTHS
Fig. 1. Recurrent stenosis rate following carotid endarterectomy in asymptomatic patients using life table analysis9
0
_
i
i
i
i
10
20
30
40
_1
50
i
i
i
h
i
I
i
60
70
80
90
100
110
120
/
~
130
140
MONTHS Fig. 3. Contralateral stroke rate in asymptomatic patients undergoing carotid endarterectomy using life table analysis.
A N N A L S OF VASCULAR SURGERY
CAROTID E N D A R T E R E C T O M Y FOR ASYMPTOMA77C STENOSIS
114
% SURVIVAL
% WITHOUT STROKE
120
[2C
100 20
80
ql
81 71 53
58
51
42
37
27
21
[2
8
8
8
7
3
3
3
12o
8C
2
q i
83
72
b4
5 ~ 0 5 3 ~ 43
60
6C
40
4C
20
2s
0
I
r
I
I
I
I
I
I
I
I
10
20
30
40
50
60
70
80
90
100
~
130
0
140
28
23
9
...............................
7
7
12
I
110 120
38
7
I
I
I
I
I
I
I
I
I
I0
20
30
40
50
60
70
80
90
6
3
I 9
100
3
3
2
I
I
r
ll0
120
130
140
MONTHS
MONTHS
Fig, 4. Overall stroke rate in asymptomatic patients undergoing carotid endarterect0my using life table analysis,
Fig, 5. Overall survival in asymptomatic patients undergoing carotid endarterectomy using life table analysis,
private vascular surgeons, underscoring the importance of Surgical training. In reviewing the first phase operative results in the Veteran's Administration (VA) cooperative clinical trial on asymptomatic carotid stenosis, Towne and colleagues [14] reported a combined stroke and death rate of 4.3%, which was derived from teaching services at university-affiliated VA hospitals. Our own results confirm the value of a supervised training program in a series of 120 operations unaccompanied by stroke or death in patients. These results are continued in the form of long-term ipsilateral stroke protection. Furthermore, surgeons having graduated from approved programs have demonstrated an ability to maintain these low complication rates [15]. Continued and frequent performance of the operation is also important in obtaining low perioperative morbidity and
mortality rates. Rubin and coworkers [16], in reviewing results from a metropolitan community, have recently reported a statistically significant decrease in the incidence of stroke after carotid endarterectomy when performed by surgeons whose clinical practice exceeded five carotid endarterectomies per year. Thus, adequacy of training as well as a continued interest and experience in carotid endarterectomy yields superior results.
CONCLUSIONS Carotid endarterectomy performed on patients with asymptomatic carotid stenosis is a safe and effective operation in this clinical series. Analysis of
TABLE II.mlncidence of stroke in patients undergoing carotid endarterectomy for asymptomatic carotid artery stenoses
Investigator
No. of patients
Perioperative stroke (%)
Thompson [6] Hertzer [7] Moneta [8] Caracci [9] Current series
132 95 56 79 120
1.2 3.4 1.8 2.5 0
Operative mortality (%)
Mean follow-up (mo.)
Ipsilateral (%)
55.1 38 24 21 36
--* --* 4 0 4.5
0 1.1 1.8 1.3 0
Contralateral (%) --* --* 16 0 7.3
Total (%) 5.8 8.4 21.8 2.5 11.8
*Data not reported
TABLE IIl.--Incidence of stroke in patients with nonoperative
carotid artery stenoses
Investigator
No, of patients
Thompson [6] Hertzer [7] Moneta [8] Caracci [9]
138 195 73 62
*Not reported
Mean follow-up (mo.) 1week-124months 33 24 21
management of asymptomatic
Ipsilateral
Contralateral
Total
(%) --* --* 19% 18%
(%) --* --* --* --*
(%) 17.4% 12.8% 19% 18%
VOLUME 5 No 2 - 1991
CAROTID ENDARTERECTOMY FOR AS YMPTOMAT1C STENOSIS
our results suggests that low morbidity can be achieved in a vascular fellowship program. This underscores our opinion that technical proficiency with performance of the operative procedure is of major importance. Routine clinical audits of results with carotid endarterectomy are recommended.
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115
7. HERTZER NR, FLANAGAN RA Jr, O'HARA PJ, et al. Surgical versus nonoperative treatment of asymptomatic carotid stenosis. Ann Surg 1986;204:163-171. 8. MONETA GL, TAYLOR DC, NICHOLLS SC, et al. Operative versus nonoperative management of asymptomatic high grade internal carotid artery stenosis: improved results with endarterectomy. Stroke 1987;18:1005-1010. 9. CARACCI BF, ZUKOWSKI AJ, HURLEY JJ, et al. Asymptomatic severe carotid stenosis. J Vasc Surg 1989;9: 361-366. 10. CALLOW AD, CAPLAN LR, CORRELL JW, et al. Carotid endarterectomy: what is the current status? Am J Med 1988:85:835-838. 11. BROTT T, THALINGER K. The practice of carotid endarterectomy in a large metropolitan area. Stroke 1984;15:950955. 12. EASTON JD, SHERMAN DG. Stroke and mortality rate in carotid endarterectomy: 228 consecutive operations. Stroke 1977:8: 565-568. 13. KRUPSKI WC, EFFENEY DJ, GOLDSTONE J, et al. Carotid endarterectomy in a metropolitan community: comparison of results from three institutions. Surgery 1985;98: 492499. 14. TOWNE JB, WEISS DG, HOBSON RW If. First phase report of Cooperative Veterans Administration asymptomatic carotid stenosis study--operative morbidity and mortality. J Vase Surg 1990;1l:252-259. 15. BAKER WH, LITTOOY FN, GREISLER HP, et al. Carotid endarterectomy in private practice by fellowship-trained surgeons. Letter to the Editor. Stroke 1987;18:957958. 16. RUBIN JR, PITLUK HC, KING TA, et al. Carotid endarterectomy in a metropolitan community: the early results after 8,535 operations, d Vasc Surg 1988;7:256-260.
