The outcome of external carotid endarterectomy during routine carotid endarterectomy

The outcome of external carotid endarterectomy during routine carotid endarterectomy Joseph P. Archie, Jr, PhD, MD, Raleigh, NC Purpose: This study is an analysis of the outcome of a common method of management of the external carotid artery (ECA) during routine carotid endarterectomy (CEA). Methods: Between 1986 and 1997, 1069 primary CEAs were performed with a combination of proximal eversion technique and blind distal endarterectomy on the ECA. Of these, 973 CEAs (91%) had 1 or more postoperative duplex scans that included the ECA. Both preoperative and early postoperative studies were performed on 313 of these CEAs. Intraoperative post-cea continuous-wave Doppler scans identified low flow or occlusion of the ECA in 37 CEAs (4%). These ECAs were isolated and repaired. Results: The early post-cea duplex scan velocities were 143 ± 81 cm/s (mean ± l standard deviation of the mean). In the first 6 months after the CEAs, 692 ECAs (72%) had <50% stenosis, 175 (18%) had 50% to 74% stenosis, 90 (9%) had 75% stenosis, and 9 (1%) were occluded. Of the 37 repaired ECAs, 20 (54%) had <50% stenosis, 10 (27%) had 50% to 74% stenosis, 5 (14%) had 75% stenosis, and 2 (5%) were occluded. The cumulative life-table 50% stenosis rate was 36% at 1 year, 40% at 3 years, 48% at 5 years, and 81% at 10 years. The cumulative 75% stenosis rate was 12% at 1 year, 12% at 3 years, 15% at 5 years, and 37% at 10 years. Preoperative studies showed <50% stenosis in 152 of the 313 ECAs (48%). In the early postoperative period, 102 of these ECAs (66%) had <50% stenosis, 35 (23%) had 50% to 74% stenosis, 13 (9%) had 75% stenosis, and 3 (2%) were occluded. Of the 161 ECAs with 50% preoperative stenosis, 66 (41%) had <50% stenosis in the first 6 months after CEA, 61 (38%) had 50% to 74% stenosis, 32 (20%) had 75% stenosis, and 2 (1%) were occluded. Conclusions: Combined proximal eversion technique and blind distal ECA endarterectomy during routine CEA gives poor and unacceptable early and late outcomes. The repair of severely obstructed or occluded ECA identified during surgery after CEA has a similarly poor outcome. The technique and management of the ECA during routine CEA needs further investigation and modification. (J Vasc Surg 1998;28:585-90.) The management technique of the atherosclerotic disease in the external carotid artery (ECA) during routine carotid endarterectomy (CEA) is important. Thrombosis of the ECA and intimal flaps in the ECA with embolization into the internal carotid artery after CEA can cause neurologic deficits. l-3 Little attention has been paid to the relationship between the technique and the outcome of From the Wake Medical Center and Carolina Cardiovascular Surgical Associates. Reprint requests: Joseph P. Archie, Jr, PhD, MD, Carolina Cardiovascular Surgical Associates, 3020 New Bern Ave, Ste 560, Raleigh, NC 27610. Copyright 1998 by The Society for Vascular Surgery and International Society for Cardiovascular Surgery, North American Chapter. 0741-5214/98/$5.00 + 0 24/1/92618 the ECA. Many surgeons perform blind ECA endarterectomy with or without proximal eversion technique. This method is reported to have a 5% to 16% incidence rate of early post-cea ECA occlusion. 4-8 This occlusion rate may be improved somewhat by the intraoperative identification and repair of endarterectomy-produced high-grade stenosis or occlusion. 9 Recently, Ascer et al 10 reported a 100% ECA patency rate and an 18% incidence rate of 50% stenosis and a 10% incidence rate of 75% residual or operatively produced ECA stenosis in the first month after CEA with simple transection of the plaque at the ECA orifice. These rates were unchanged from the preoperative findings that indicated that this was a residual disease. This outcome, which averted any attempt at ECA endarterectomy, raises significant questions regarding both the advisability and the technique of ECA endarterectomy 585

586 Archie October 1998 Fig 1. Kaplan-Meier method for 50% and 75% stenosis-free intervals for the external carotid artery after carotid endarterectomy. Number at risk and standard error of the mean for each interval are given in Table II. during routine CEA. Ascer et al 10 also contributed a set of duplex-scan peak systolic velocity criteria for ECA stenosis on the basis of the magnetic resonance angiography of 60 arteries. In a prior small series, I reported an excellent ECA patency rate after aggressive proximal eversion endarterectomy combined with isolated ECA repair when intraoperative post- CEA continuous-wave Doppler scan indicated highgrade stenosis or occlusion. 9 However, these results were 3 to 6 months post-cea, and the duplex Doppler ultrasound-scan criteria used to identify residual or recurrent ECA stenosis were peak systolic velocities of 350 cm/s. These criteria are far too strict and probably identify only the stenoses that are well above 75%. The outcome results reported herein are on the basis of a large series of CEAs with early and long-term follow-up and are analyzed with current Doppler ultrasound-scan velocity criteria. 10 METHODS AND MATERIALS Patient demographics. Between 1986 and 1997, 1069 primary CEAs were performed with a uniform technique of management of the ECA. Of these CEAs, 973 had 1 or more postoperative duplex scans that included the ECA. Preoperative scans performed with the same equipment and by the same technologist were obtained on 313 of these (32%). There were 545 CEAs performed on men and 428 on women, with an age range of 69 ± 9 years (mean ± 1 standard deviation of the mean). The indications for CEA were transient ischemic attack in 36%, reversible ischemic neurologic deficit or stroke in 18%, global or nonlateral ischemia in 10%, and asymptomatic 75% stenosis in 36%. The risk factors included hypertension in 59%, coronary artery disease in 70%, prior or continued smoking in 75%, and diabetes mellitus in 14%. The perioperative clinical outcomes have been reported previously for most of this group. 11-13 Technique of external carotid endarterectomy. The endarterectomy begins in the common carotid artery proximal to the major atherosclerotic disease. A curved right-angle clamp gently is advanced circumferentially to develop a deep media dissection plane. The intima and the media are divided circumferentially along the proximal edge of the clamp to minimize the degree of dissection under the retained common carotid artery step. The endarterectomy then is carried distally to the orifice of the ECA. The ECA endarterectomy is performed before the internal carotid artery endarterectomy unless there is the unusual finding of a short segment of internal carotid artery disease. In this setting, ECA endarterectomy usually produces a 5-mm to 10-mm continuation of the deep media dissection into the internal carotid artery bulb. An otherwise potentially feathered endpoint in the bulb may be disrupted by the performance of the ECA endarterectomy first. Elastic loops are used for hemostasis on the superior thyroid artery and on the main trunk of the ECA. Pulling the elastic loop and the plaque caudad everts the proximal ECA as the endarterectomy proceeds circumferentially into the ECA. If an endpoint is not obtained, the tension on the elastic loop is released and a blind endarterectomy is continued into the distal main ECA trunk. The ECA specimen endpoint is checked for feathering and for plaque from branch arteries distal to the superior thyroid. Significant retained plaque, or distal dissection, is usually identified by the fracturing of the distal ECA specimen endpoint. If this finding is noted, the ECA is not opened and repair is not attempted unless post-cea continuous-wave Doppler-scan interrogation is severely abnormal as described below. After completion of the internal carotid artery endarterectomy, reconstruction is performed. In this series of 973 CEAs, an autologous greater saphenous vein or a synthetic patch was used in 96% of the cases. Primary closure was performed in the 4% of the CEAs in which the arteriotomy that was required to obtain a complete internal carotid artery endpoint did not extend beyond the carotid bulb. Technique of isolated external carotid artery repair. After the CEA reconstruction and the reinstitution of blood flow, continuous-wave Doppler-

Volume 28, Number 4 Archie 587 Table I. External carotid artery stenosis 2 to 6 months after 973 carotid endarterectomies ECA not repaired ECA repaired Total % Stenosis n % n % n % 0 to 49% 676 (72.2) 20 (54.1) 696 (71.5) 50% to 74% 168 (17.9) 10 (27.0) 178 (18.3) 75% to 99% 85 (9.1) 5 (13.5) 90 (9.3) Occluded ECAs 7 (0.8) 2 (5.4) 9 (0.9) All abnormal ECAs ( 50%) 260 (27.8)* 17 (45.9) 277 (28.5) ECA, external carotid artery. *P =.027, by χ 2 test with Yates correction for 0 to 49% stenosis versus all abnormal external carotid arteries. scan interrogation is performed. If there is little or no flow in the ECA, as evidenced by a low frequency thump in the main trunk, or if there is a low flow in the main trunk and a high frequency signal over the branching segments, the ECA is isolated and repaired. The distal branches are dissected out and are individually controlled with elastic loops as the retained plaque or dissection usually extends to them. A small vascular clamp is placed at the origin of the ECA that has been previously cleared of plaque. A longitudinal arteriotomy is made in the main ECA trunk, and a completion endarterectomy is performed. The arteriotomy is closed either primarily or with a small patch. Of the 973 CEAs in this series, 37 (4%) had isolated ECA repair. The adequacy of the repair is confirmed by continuous-wave Doppler scan. Duplex scan follow-up. A duplex scan followup was recommended and performed with patient compliance at approximately 2 months and 6 months and annually. All of the scans were performed by 1 of 2 experienced, certified registered nurse technologists with 7.5-MHz B-mode, 5- MHz pulsed Doppler scan equipment. Initially, this was an Ultramark 8 and later an Ultramark 9 (Advanced Technology Lab, Bothell, Wash). The ECA peak systolic velocity criteria used were on the basis of the following data of Ascer et al 10 : <150 cm/s = <50% stenosis, 150 cm/s to 250 cm/s = 50% to 74% stenosis, and 250 cm/s = 75% stenosis. The preoperative and postoperative velocities were 154 ± 89 cm/s and 155 ± 88 cm/s, respectively (P =.9, by paired t test). The medians for both studies were 130 cm/s. The precision of the repeated measurements of ECA peak systolic velocity was determined by pre-cea, early, and post-cea measurements on 272 unoperated contralateral ECA. The mean intra-artery difference in the 2 measurements was 2 cm/s, and the mean absolute value of the difference was 19 cm/s. Statistical analysis. The summary data are presented as the mean ± 1 standard deviation of the mean or as nominal values with percentages and, when indicated, as the ±95% confidence interval. Analysis was performed with χ 2 test with Yates correction, paired and unpaired 2-tailed tests, Kaplan- Meier method, and linear regression. The computations were performed with a software program (JMP, SAS Institute, Cary, NC). RESULTS One patient had a mild intraoperative embolic stroke as a result of the placement of a clamp at the origin of the ECA to perform an isolated repair. Residual ECA atheroma was noted in the lumen and in the clamp when the ECA arteriotomy was made. The clamp apparently fractured the end of the proximal segment of plaque, which produced an embolus into the internal carotid artery. The neurologic deficit was not noted until the first postoperative day when the patient ambulated. The patient had mild motor weakness in the contralateral leg that did not completely resolve. No other neurologic morbidity or mortality was attributable to the ECA in this series. However, 3 patients had a perioperative stroke of unknown cause 12 to 96 hours after CEA. Although all 3 patients had normal duplex scan results at the time, the scan results at 6 to 8 weeks revealed abnormal ECA in 2 cases (176 cm/s and 230 cm/s). The possible role of these abnormal ECAs in perioperative stroke is speculative. Table I shows the ECA residual or restenosis in the first 6 months after 973 CEAs. Only 71.5% of the ECAs were normal or had <50% stenosis. Occlusion was identified in 0.9% of the CEAs. The early post-cea peak systolic velocities in the ECAs were 143 ± 81 cm/s. Of the 37 that underwent isolated repair, only 54% of the ECAs were normal or had <50% stenosis. ECA occlusion was identified in 5% of the ECAs. Fig 1 and Table II show the life

588 Archie October 1998 Table II. Life table for 50% stenosis-free and 75% stenosis-free intervals 50% Time Stenosis free (months) Proportion SD No. failed No. sensored No. at risk 2 0.827 0.012 168 129 973 6 0.694 0.016 109 71 676 12 0.638 0.017 40 116 496 24 0.613 0.017 13 80 340 36 0.598 0.018 6 54 247 48 0.554 0.020 14 36 187 60 0.521 0.022 8 36 137 72 0.465 0.026 10 26 93 84 0.424 0.029 5 16 57 96 0.389 0.033 3 10 36 108 0.304 0.042 5 5 23 120 0.187 0.049 5 8 13 75% Time Stenosis free (months) Proportion SD No. failed No. sensored No. at risk SD, Standard deviation of the mean. 2 0.930 0.008 68 161 973 6 0.891 0.010 31 99 744 12 0.880 0.011 8 172 614 24 0.878 0.011 1 128 434 36 0.875 0.012 1 75 305 48 0.856 0.014 5 65 229 60 0.850 0.015 1 48 159 72 0.811 0.022 5 38 110 84 0.800 0.025 1 26 67 96 0.760 0.036 2 11 40 108 0.675 0.056 3 10 27 120 0.627 0.070 1 13 14 table analysis for stenosis-free periods for <50% stenosis and <75% stenosis. The cumulative 50% stenosis rate was 36% at 1 year, 40% at 3 years, 48% at 5 years, and 81% at 10 years. The cumulative 75% stenosis rate was 12% at 1 year, 12% at 3 years, 15% at 5 years, and 37% at 10 years. For the 313 ECAs with pre-cea and post-cea duplex scans, the peak systolic velocities were 176 ± 95 cm/s and 140 ± 77 cm/s, respectively (P <.001). Overall, 206 of the 313 ECAs (66%) had <50% stenosis after CEA. Of the 301 ECAs that did not undergo isolated repair, 199 (66%) had <50% stenosis after surgery. Table III shows the number of ECAs that fell into 4 post-cea stenosis categories in the first 6 months. These data are divided between the 152 ECAs with <50% stenosis before surgery and the 161 ECAs with 50% stenosis before surgery. The group with <50% pre-cea stenosis had a better outcome than those with 50% pre-cea stenosis. DISCUSSION The results of this study indicate that a common technique of management of the ECA during routine primary CEA gives poor early and late results. Overall, only 72% of the ECAs (±2.8%; 95% confidence interval [CI]) were either normal or had <50% stenosis early after CEA. Severe stenosis of 75% or occlusion were identified in 10% of the cases (±2.0%; 95% CI). The ECAs that had <50% stenosis before surgery had only a 74% (±6.9%; 95% CI) incidence rate of <50% early postoperative stenosis. The ECAs with 50% pre-cea stenosis had a 58% (±7.6%; 95% CI) incidence rate of <50% early postoperative stenosis. The isolated repair of severely obstructed ECA after CEA had a 54% incidence rate of <50% stenosis after CEA. ECA stenosis continues to progress significantly in the 10 years after CEA. If these results are representative of those obtained by other surgeons with similar techniques of ECA management during routine CEA, then improvements in current or new approaches in management are indicated. Such a novel approach to ECA management has been suggested by Ascer et al. 10 They used the simple technique of dividing circumferentially the plaque at the origin of the ECA. They found 89 of 116 CEAs (78%) to have <50% stenosis before CEA and 93 (82%) to have <50% stenosis early after CEA.

Volume 28, Number 4 Archie 589 Table III. External carotid artery stenosis before and 2 to 6 months after 313 carotid endarterectomies Preoperative ECA stenosis Postoperative 0 to 49% 50% ECA stenosis Not repaired Repaired Total Not repaired Repaired Total n % n % n % n % n % n % 0 to 49% 110 75.3 3 50.0 113 74.3 89 57.4 4 66.6 93 57.8 50% to 74% 25 17.1 2 33.3 27 17.8 38 24.5 1 16.7 39 24.2 75% to 99% 9 6.2 1 16.7 10 6.6 28 18.1 1 16.7 29 18.0 Occluded ECAs 2 1.4 0 0 2 1.3 0 0 0 0 0 0 All abnormal ECAs ( 50%) 36 24.7 3 50.0 39 25.7 66 42.6 2 33.3 68 42.2 Total 146 100 6 100 152 100 155 100 6 100 161 100 ECA, External carotid artery. In the study reported herein, with the same velocity criteria, 152 of 313 ECAs (47%) had preoperative stenosis of <50%. This difference could be caused by machine variability or by more severe ECA disease in the current study. In addition, Ascer et al 10 found a minimal progression of stenosis in the intact ECAs at a mean follow-up of 20 months. This is in contrast to the progressive stenosis early and late after ECA endarterectomy as illustrated in Fig 1. They did not find a correlation between the degree of ECA stenosis and internal carotid artery stenosis. Intraoperative post-cea reconstruction duplex scanning or other imaging technology would probably identify more defects than does continuouswave Doppler scan. Only severe defects were repaired in this study. Although the outcome of these repairs is marginal, more aggressive ECA revision criteria, such as 50% stenosis, may lead to improved results. The optimal management technique for the ECA during routine CEA remains undefined. These results suggest that the technique used in this study, combined proximal eversion technique and blind distal endarterectomy, results in an approximate 30% incidence rate of retained significant plaque or intimal flap or both. What could we do differently? The real problem may be inherent in blind endarterectomy to the level of arterial branching. The elastic loops used for hemostasis could have produced plaque fracture before the endarterectomy. However, it is unlikely that they are equally as traumatic or more traumatic than a clamp. Perhaps the isolation of the major ECA branches before endarterectomy would improve outcome. The length of the main ECA trunk before branching into the occipital, temporal, mandibular, and facial arteries may be an important determinant, as could be the highly variable location of the origin of the superior thyroid artery. However, in this study, these dimensions were not measured. Because emboli from the orifice of a thrombosed ECA or from the residual ECA disease have been identified as a cause of perioperative neurologic events, 1-3 it may be beneficial to clear the proximal ECA segment of atheroma. This has the added advantage of the ability to safely place a clamp at the ECA origin for isolated repair. This study is the largest series and the longest follow-up of the outcome of the ECA after CEA. The early and late outcomes in terms of recurrent ECA stenosis are inferior to what is routinely obtained with the internal carotid artery, which is managed more precisely. Even though the complications from the ECA are unusual, given the quest to optimize CEA outcome, an improved technique for ECA management is needed. REFERENCES 1. Moore WS, Martello JY, Quinones-Baldrich WG, Ahn SS. Etiologic importance of the intimal flap of the external carotid artery in the development of postcarotid endarterectomy stroke. Stroke 1990;21:1497-502. 2. Countee RW, Vijayanathan T, Wu SZ. External carotid occlusion as a cause of recurrent ischemia after carotid endarterectomy. Neurosurgery 1982;11:518-21. 3. Sundt TM, Houser OW, Whisnant JP, Fode NC. Correlation of postoperative and two year follow-up angiography with neurologic function in 99 carotid endarterectomies in 86 consecutive patients. Ann Surg 1986;203:90-100. 4. Barnes RW, Nix LM, Nichols BT, Wingo JP. Recurrent versus residual carotid stenosis. Ann Surg 1986;203:652-60. 5. Seifert KB, Blackshear WM Jr. Continuous-wave Doppler in the intraoperative assessment of carotid endarterectomy. J Vasc Surg 1985;2:817-20. 6. Hertzer NR, Beven EG, Modic MT, et al. Early patency of the carotid artery after endarterectomy: digital subtraction angiography after 262 operations. Surgery 1982;92:1049-57. 7. Diaz FG, Patel S, Boulos R, et al. Early angiographic changes following carotid endarterectomy. Stroke 1989;11:135-8. 8. Towne JB, Weiss DG, Hobson RW II. First phase report of

590 Archie October 1998 cooperative Veterans Administration asymptomatic carotid stenosis study operative morbidity and mortality. J Vasc Surg 1990;11:252-9. 9. Archie JP. Management of the external carotid artery during carotid endarterectomy. J Cardiovasc Surg 1992;33:62-6. 10. Ascer E, Gennaro M, Pollina RM, Salles-Cunha S, Lorenson E, Yorkovich WR, et al. The natural history of the external carotid artery after carotid endarterectomy: implications for management. J Vasc Surg 1996;23:582-6. 11. Archie JP Jr. Technique and clinical results of carotid stump back-pressure to determine selective shunting during carotid endarterectomy. J Vasc Surg 1991;13:319-27. 12. Archie JP Jr. Carotid endarterectomy with reconstruction techniques tailored to intraoperative findings. J Vasc Surg 1993;17:141-51. 13. Archie JP. Management of acute postendarterectomy neurological deficits. In: Whittemore AD, editor. Advances in vascular surgery, vol 3. Chicago: Mosby, Inc; 1994. p. 97-111. Submitted Apr 29, 1998; accepted Jun 24, 1998. Your comprehensive reference to valuable research information... Now you can have easy access to research information with the 12-year cumulative author and subject index to Volumes 1-22 of Journal of Vascular Surgery. The Cumulative Index is your comprehensive reference guide, including a list of every article in the Journal from 1984 through 1995. All articles are indexed both by subject and by author. The Cumulative Index features: Offset and bold Subject Headings that make searching for subject entries easier Subject Entries containing complete article title, author(s), year of publication, volume, and page Author Entries listing author(s), article title, author-to-author referral, year of publication, volume, and page Order the Journal of Vascular Surgery Cumulative Index today! Please send me the 12-Year YES! Cumulative Index to Journal of Vascular Surgery (1984-1995). I ve indicated my method of payment below. All prices include shipping. $75.00 U.S. $85.60 Canada* $80.50 International *Includes Canadian GST. Payment must accompany your order. Check enclosed (U.S. funds, payable to Journal of Vascular Surgery) MasterCard VISA Discover Credit Card # Exp. Date Signature Name Institution Address City State ZIP Country To order, just call Or return coupon to: 1-800-453-4351 Mosby, Inc. Outside the U.S.: 314-453-4351 Journal Subscription Services Fax: 314-432-1158 11830 Westline Industrial Dr. St. Louis, MO 63146 U.S.A.