- Email: [email protected]
Results of routine shunting and patch closure during carotid endarterectomy
The American Journal of Surgery (2012) 203, 613– 617
North Pacific Surgical Association
Results of routine shunting and patch closure during carotid endarterectomy Marcus R. Kret, M.D., Brandon Young, B.S., Gregory L. Moneta, M.D., Timothy K. Liem, M.D., Erica L. Mitchell, M.D., Amir F. Azarbal, M.D., Gregory J. Landry, M.D.* Division of Vascular Surgery, OP-11, Oregon Health and Science University, 3181 SW Sam Jackson Park Road, Portland, OR 97239, USA KEYWORDS: Carotid endarterectomy; Shunt; Patch angioplasty; Stroke
Abstract BACKGROUND: The role of shunting and patching during carotid endarterectomy remains controversial. METHODS: This is a retrospective case series evaluating consecutive patients undergoing carotid endarterectomy with routine shunting and patching. The primary endpoints were perioperative stroke, arterial injury, and lesion recurrence by duplex. RESULTS: Of the 220 operations performed, 43% were for symptomatic disease. Successful shunt placement occurred in 98%, with no shunt-related injuries. There was 1 minor perioperative stroke and no major strokes. At a mean follow-up of 24 months (median ⫽ 12 months), there was 1 restenosis potentially related to shunt placement. The incidence of asymptomatic ⬎50% stenosis in the patched segment was 8%. CONCLUSIONS: A combined policy of routine shunting and patching simplifies intraoperative decision making with results that rival or exceed those of trials in which their use was not standardized. Shunts need not be avoided because of concern of arterial injury. © 2012 Elsevier Inc. All rights reserved.
Carotid endarterectomy is an effective means of stroke prevention in patients with high-grade symptomatic (⬎70%) or asymptomatic (⬎60%) internal carotid artery stenosis and has been proven to be superior to medical management alone.1,2 Shunt placement preserves ipsilateral cerebral perfusion during the period of carotid clamping and may decrease the incidence of perioperative stroke because Presented at the North Pacific Surgical Association Annual Meeting, Vancouver, BC, Canada, November 11–12, 2011. * Corresponding author. Tel.: ⫹1-503-494-7593; fax: ⫹1-503-4944324. E-mail address: [email protected] Manuscript received October 18, 2011; revised manuscript December 21, 2011
0002-9610/$ - see front matter © 2012 Elsevier Inc. All rights reserved. doi:10.1016/j.amjsurg.2011.12.005
of cerebral hypoperfusion. Despite numerous investigations into the safety and efficacy of carotid shunting, its role remains controversial.3,4 There are essentially 3 approaches to carotid shunting: routine shunt placement, selective shunt placement, and routine nonshunting. Advocates of routine shunting suggest that this practice promotes technical proficiency and avoids the excess time, inconvenience, and cost associated with neuromonitoring techniques often used for selective shunt placement. Alternately, proponents of selective shunting argue that although it may decrease the risk of perioperative stroke, shunt placement is only truly necessary in a small percentage of patients and that routine shunting may lead to unnecessary shunt placement in as many as 85% of patients.5 It can also be argued that shunt
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The American Journal of Surgery, Vol 203, No 5, May 2012
placement itself can lead to complications, including air or atheromatous emboli, arterial dissection, and acute arterial occlusion.6 In addition, despite data indicating a decreased risk of perioperative arterial occlusion as well as a decreased risk of subsequent restenosis,7 carotid patch angioplasty is not universally used in carotid endarterectomy. In our practice, we have for many years had a policy of routine shunt placement with patch arteriotomy closure. Thus, in this study, we sought to review operative and ultrasound records to quantify shunt-related arterial injury and evaluate a policy of routine shunt placement and patch closure during carotid endarterectomy.
Sundt-type shunts (Integra Neurosciences, Plainsboro, NJ) were used in 72% of cases (n ⫽ 158) and Pruitt-Inahara (LeMaitre Vascular, Burlington, MA) in 19% (n ⫽ 42). In 1 case, the shunt type was not specified, and in another an Argyle shunt (Covidien, Mansfield, MA) was used. In the remaining 18 cases, no shunt was ultimately used. Difficulty with shunt placement was noted in only 5 patients (2%). In 2 cases, the internal carotid artery was too small to accommodate the shunt, whereas a third was noted to have an exceedingly tortuous common carotid artery. There was 1 case in which the shunt could only be inserted 1 to 2 cm into the distal internal carotid artery, and, despite forward flow through the shunt, it could not be kept in place through the completion of patch closure as planned. Finally, there was 1 instance in which flow within the shunt could not be detected by Doppler despite the successful insertion of 2 different types of shunt. When a deliberate decision to skip shunt placement was made, it was based on a mean internal carotid artery stump pressure ⬎50 mm in 11 of 13 cases. In the 2 additional cases, the operation was performed under cervical block anesthesia, and neurologic status was preserved during the period of carotid cross-clamping. No injuries related to shunt placement were observed. Patch closure was used in 205 operations (93%). The most commonly used patch types were polyester (64%, n ⫽ 141) and bovine pericardium (26%, n ⫽ 58). The remainder of cases used saphenous vein (4%), polytetrafluoroethylene (1%), or no patch at all (7%). Primary closure was reserved for instances in which the operating surgeon noted the native arteries to be of a particularly large diameter. The mean follow-up was approximately 24 months (median ⫽ 12 months). Information regarding the postoperative course was available in 176 patients. There were 3 perioperative transient ischemic attacks (2%) noted and 1 minor perioperative stroke (1%) that manifested as a transient facial droop 1 month after surgery. There were no major strokes. In addition, there were 7 transient cranial nerve injuries (4%); these typically manifest as facial numbness. The availability of vascular laboratory data before 2004 was very limited, and, as a result, follow-up carotid duplex data were only available for 115 patients (52%) (Table 1). Of the 105 patients with no vascular laboratory data available, 74 (71%) did have continued vascular surgery clinic follow-up. Of the available studies, there were 12 patients with increased peak systolic velocities in either the proximal common carotid or distal internal carotid, which could be interpreted as a shunt-related event. However, a meticulous case review revealed normalized velocities on subsequent follow-up studies in 4 patients. In 4 others, globally elevated peak systolic velocities were attributed to a contralateral occlusion rather than an ipsilateral restenosis; 2 of these patients subsequently had normalized duplex findings. Two additional patients showed no evidence of stenosis on Bmode ultrasonography. Finally, 1 patient had elevated proximal common carotid artery velocities both pre- and post-
Methods The study was a retrospective review of a prospectively maintained database at an academic medical center. Intraand postoperative data were evaluated for consecutive patients undergoing carotid endarterectomy during the period beginning in January 2000 and ending in June 2010. Basic demographic information and comorbidities were recorded. Operative data included shunt placement, the type of shunt used, whether difficulty was encountered with shunt placement, and the type of patch used for arteriotomy closure. Postoperative complications including stroke, cranial nerve injury, and wound healing were reviewed and recorded. Results of arterial duplex ultrasonography from pre- and postoperative periods were evaluated for evidence of restenosis at the site of shunt placement (ie, the common carotid artery proximal to the site of the endarterectomy or the internal carotid artery distal to the site of endarterectomy) and within the patched segment (primarily the proximal and midcervical internal carotid artery). The primary endpoints were perioperative stroke, arterial injury, and lesion recurrence as assessed by arterial duplex ultrasound. The vast majority of operations were performed under general anesthesia. After the administration of systemic heparin, the internal, external, and common carotid arteries are sequentially clamped. The shunt is inserted into the distal internal carotid artery, allowed to back bleed, and then inserted proximally into the common carotid artery. Flow is confirmed within the shunt by continuous-wave Doppler. Once the endarterectomy is complete, the arteriotomy is routinely closed with a patch. After surgery, patients were advised to undergo a follow-up duplex evaluation in the early postoperative period and every 6 months thereafter.
Results Over the selected time period, 220 procedures were performed: 43% for symptomatic disease (n ⫽ 95) and 57% for asymptomatic disease (n ⫽ 125). Shunt placement was attempted in 207 cases (94% of total carotid endarterectomy) and was successful in 202 (98% of those attempted).
M.R. Kret et al. Table 1
Routine shunting during carotid endarterectomy
615
Average peak systolic velocities (cm/s) Peak systolic velocity (mean ⫾ standard deviation) Proximal common carotid artery
Preop (n ⫽ 106) 0–3 mo postop (n ⫽ 72) 3–12 mo postop (n ⫽ 61) 1–2 y postop (n ⫽ 62) ⬎2 y postop (n ⫽ 52)
88 95 92 93 93
⫾ ⫾ ⫾ ⫾ ⫾
24 31 21 31 23
Distal common carotid artery 87 102 100 96 99
⫾ ⫾ ⫾ ⫾ ⫾
73 43 44 39 50
Proximal internal carotid artery 419 85 98 90 90
⫾ ⫾ ⫾ ⫾ ⫾
143 45 42 39 39
Distal internal carotid artery 94 92 98 90 88
⫾ ⫾ ⫾ ⫾ ⫾
31 38 26 23 24
Preop ⫽ preoperative; postop ⫽ postoperative.
operatively because of a large proximal plaque burden and was thus not felt to have a restenosis attributable to shunt placement. There was 1 patient with persistent, mildly elevated velocities in the distal internal carotid; a review of the computed tomography scan of her neck obtained for an unrelated issue did suggest a narrowing in this segment. This patient did not develop symptoms related to the lesion during the follow-up period. In total, there were 17 patients who exhibited elevated velocities in the proximal internal carotid artery over the study period. After reviewing each of these cases, the incidence of asymptomatic ⬎50% stenosis in the patched portion was determined to be 8% (n ⫽ 9). Follow-up studies ultimately showed normal velocities in this segment in 6 patients, and in another no evidence of stenosis was seen on B-mode imaging. In 1 case, a pseudoaneurysm developed at the distal, posterior aspect of the patch several years after the original operation. This patient eventually underwent revision using a greater saphenous vein interposition graft. The notable recurrences include 1 early asymptomatic recurrence associated with a focal stenosis that was treated with a carotid stent. In addition, there was 1 instance in which complete ipsilateral carotid occlusion was discovered 8 years after the original operation. This patient had a single postoperative follow-up visit with vascular surgery and was subsequently seen regularly by her primary care provider only. The occlusion was noted after she presented to her primary care provider with syncope.
Comments This series shows the safety and efficacy of routine carotid shunting with patch arteriotomy closure during carotid endarterectomy. The low incidence of perioperative stroke in our series despite the high proportion of symptomatic patients compared with most single-institution series suggests that carotid shunting combined with patch arteriotomy closure is an effective means to prevent harmful neurologic effects that result from a lack of cerebral perfusion. These data are in line with published data on routine shunt and patch use during carotid endarterectomy. A recent
review examining the use of shunts in carotid endarterectomy cited a perioperative stroke rate of 1.4% for routine shunting based on the pooled results of 14 previous studies.4 Bellosta et al8 used a similar strategy of routine shunt placement with patch closure and reported a perioperative stroke rate of .7% and asymptomatic ⬎50% restenosis in 1.7% over a mean follow-up interval of 24 months. In our series, 9 patients (8%) had evidence of restenosis in the patched segment although only 1 required subsequent reintervention. Despite numerous reports showing the safety of routine shunting during carotid endarterectomy, this approach remains controversial. The 2009 update of the Cochrane Review3 of routine versus selective shunting during carotid endarterectomy concluded not only that evidence remained insufficient to support or refute the use of carotid shunting but also that no single method for neurologic monitoring in selective shunting has proved superior. Recently, AbuRahma et al5 compared routine versus selective shunt placement in 200 prospectively randomized patients. Perioperative stroke rates were 2% and 3%, respectively, a difference that did not reach significance. This led the authors to conclude that the decision to shunt routinely or selectively should be based on the surgeon’s level of comfort with either technique. Most would agree that carotid endarterectomy performed on an awake patient under cervical block anesthesia provides the most reliable method to assess neurologic function.9 –11 However, this approach can be compromised by patient anxiety or claustrophobia, limitations on positioning because of neck fixation, and more complicated dissections required in reoperative fields. Furthermore, shunting based on the development of neurologic symptoms results in the need for urgent shunt placement, which can be much more anxiety provoking and less controlled than elective shunting immediately after carotid cross-clamping. When general anesthesia is used, some form of adjunctive testing must be used to determine whether a shunt should be placed. Two of the more common approaches used are measurement of internal carotid artery stump pressure and electroencephalographic (EEG) monitoring. In our series, mean carotid stump pressures ⬎50 mm Hg were cited as evidence of
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preserved cerebral perfusion in 11 patients. This has generally been considered a safe threshold, and none of the patients in our series suffered a perioperative neurologic event. Establishing safe, consistent threshold parameters for shunt placement has proven difficult. In multiple studies, carotid stump pressure ⬎50 mm Hg has been shown to identify 96% to 97% of patients with concurrent EEG changes.12,13 Despite these findings, Harada et al13 argued that the sensitivity and specificity for this threshold stump pressure (89% and 61%, respectively) were suboptimal for use as a standalone test to determine whether or not to shunt. Despite low rates of perioperative stroke, neurologic monitoring with selective shunting only approximates the risk of cerebral malperfusion. As shown by those studies performed in awake patients, a small percentage will suffer from cerebral ischemia despite normal EEG tracings and carotid stump pressure. Hans and Jareunpoon11 compared these measures in operations performed under cervical block anesthesia. Beyond the threshold stump pressure of 50 mm Hg, only 1.4% of patients required shunting based on changes in neuroexamination. Interestingly, of those that required shunts, only 40.6% showed ischemic changes on the electroencephalogram. Thus, the authors concluded that awake neurologic monitoring is the most sensitive indicator of the need for carotid shunt. Critics of routine shunting argue that this approach unnecessarily exposes a large number of patients to the risks of shunting. Frawley et al6 analyzed a series of 259 consecutive carotid endarterectomy using intraoperative thiopental for neuroprotection and documented a perioperative stroke rate of 1.7%. Although EEG changes occurred with carotid artery clamping in nearly 20% of patients, no strokes occurred in these patients. Thus, the authors argued that a certain number of strokes will occur despite all efforts at prevention and that thiopental cerebral protection eliminates strokes caused by complications of shunt placement. Similarly, Samson et al14 published a series of 654 carotid endarterectomies performed without a shunt leading to a 3% incidence of stroke or a TIA. Although they acknowledge that in patients with minimal internal carotid artery back bleeding, shunts may offer the potential to decrease the risk of stroke, they counter that these patients would then be subject to the risks of carotid artery shunting. Although the inherent risks remain 1 of the major arguments against routine carotid shunting, these were not observed in our series. In 202 patients in whom shunt placement was attempted, no instances of arterial dissection, distal embolization, or vessel occlusion were noted. There were 12 patients who had elevated peak systolic velocities in the proximal common or distal internal carotid artery on at least 1 follow-up duplex scan. Although elevated velocities in these locations raise the possibility of a shunt-associated lesion, after reviewing each of these cases, only one appeared to have an actual stenosis with a potential relationship to shunt placement. Among those with elevated veloc-
ities deemed not to have a true stenosis, 2 trends emerged. First, many of the elevated velocities normalized on subsequent imaging studies. In others, the velocity increases were observed in the presence of a contralateral occlusion. The phenomenon of increased blood flow velocities opposite a contralateral occlusion has been recognized in multiple previous studies evaluating duplex parameters of carotid stenosis.15,16 As a result, these findings were interpreted as normal in our analysis. Ultimately, our results indicate that essentially no immediate complications and very few, if any, harmful long-term sequelae result from shunt placement. We believe that the routine combination of shunting and patching simplifies intraoperative decision making with results that rival or exceed those of trials in which their use was not standardized. In addition, routine shunting avoids the excess cost associated with an electroencephalogram or other neurologic monitoring techniques. Furthermore, this strategy can improve surgeons’ familiarity and facility with shunt placement, particularly when trainees are involved in these operations. Shunts need not be avoided because of the concern for arterial injury.
References 1. Executive Committee for the Asymptomatic Carotid Atherosclerosis Study. Endarterectomy for asymptomatic carotid artery stenosis. JAMA 1995;273:1421– 8. 2. North American Symptomatic Carotid Endarterectomy Trial Collaborators. Beneficial effect of carotid endarterectomy in symptomatic patients with high-grade carotid stenosis. N. Engl. J. Med. 1991;325: 445–53. 3. Rerkasem K, Rothwell PM. Routine or selective carotid artery shunting for carotid endarterectomy (and different methods of monitoring in selective shunting). Cochrane Database Syst Rev 2009;4:CD000190. 4. AbuRahma AF, Mousa AY, Stone PA. Shunting during carotid endarterectomy. J Vasc Surg 2011;54:1502–10. 5. AbuRahma AF, Stone PA, Hass SM, et al. Prospective randomized trial of routine versus selective shunting in carotid endarterectomy based on stump pressure. J Vasc Surg 2010;51:1133– 8. 6. Frawley JE, Hicks RG, Gray LJ, et al. Carotid endarterectomy without a shunt for symptomatic lesions associated with contralateral severe stenosis or occlusion. J Vasc Surg 1996;23:421–7. 7. Rerkasem K, Rothwell PM. Patch angioplasty versus primary closure for carotid endarterectomy. Cochrane Database Syst Rev 2009;4; CD000160. 8. Bellosta R, Luzzani L, Carugati C, et al. Routine shunting is a safe and reliable method of cerebral protection during carotid endarterectomy. Ann Vasc Surg 2006;20:482–7. 9. Calligaro KD, Dougherty MJ. Correlation of carotid artery stump pressure and neurologic changes during 474 carotid endarterectomies performed in awake patients. J Vasc Surg 2005;42:684 –9. 10. McCarthy RJ, McCabe AE, Walker R, et al. The value of transcranial Doppler in predicting cerebral ischaemia during carotid endarterectomy. Eur J Vasc Endovasc Surg 2001;21:408 –12. 11. Hans SS, Jareunpoon O. Prospective evaluation of electroencephalography, carotid artery stump pressure, and neurologic changes during 314 consecutive carotid endarterectomies performed in awake patients. J Vasc Surg 2007;45:511–5. 12. Cherry KJ, Roland CF, Hallett JW, et al. Stump pressure, the contralateral carotid artery, and electroencephalographic changes. Am J Surg 1991;162:185–9.
M.R. Kret et al.
Routine shunting during carotid endarterectomy
13. Harada RN, Camerota AJ, Good GM, et al. Stump pressure, electroencephalographic changes and the contralateral carotid artery: another look at selective shunting. Am J Surg 1995;170:148 –53. 14. Samson RH, Showalter DP, Yunis JP. Routine carotid endarterectomy without a shunt, even in the presence of contralateral occlusion. Cardiovasc Surg 1998;6:475– 84. 15. Fujitani RM, Mills JL, Wang LM, et al. The effect of unilateral internal carotid occlusion upon contralateral duplex study: criteria for accurate interpretation. J Vasc Surg 1992;16:459 – 68. 16. AbuRahma AF, Richmond BK, Robinson PA, et al. Effect of contralateral severe stenosis or carotid occlusion on duplex criteria of ipsilateral stenoses: comparative study of various duplex parameters. J Vasc Surg 1995;22:751– 62.
Discussion Dr Ravindar Sidhu (Vancouver, BC, Canada): There are multiple strategies for cerebral protection and moni-
617
toring during carotid endarterectomy. The literature does not support the use of 1 method over another. Endarterectomy under local anesthesia provides optimal neurologic monitoring. However, if a shunt is required, patient movement and stability become significant issues. With other forms of monitoring such as an electroencephalogram, stump pressure measurements, and transcranial Doppler, shunt rates are about 15%. Routine shunting eliminates the need for monitoring but may cause unnecessary vascular trauma. In my practice, another important reason for shunting is to provide trainees with experience in shunt placement. The bottom line is that, irrespective of the method of cerebral protection, acceptable stroke and mortality rates must be attained (3% for asymptomatic and 6% for symptomatic carotid stenoses). The authors showed that their approach is indeed acceptable.
North Pacific Surgical Association
Results of routine shunting and patch closure during carotid endarterectomy Marcus R. Kret, M.D., Brandon Young, B.S., Gregory L. Moneta, M.D., Timothy K. Liem, M.D., Erica L. Mitchell, M.D., Amir F. Azarbal, M.D., Gregory J. Landry, M.D.* Division of Vascular Surgery, OP-11, Oregon Health and Science University, 3181 SW Sam Jackson Park Road, Portland, OR 97239, USA KEYWORDS: Carotid endarterectomy; Shunt; Patch angioplasty; Stroke
Abstract BACKGROUND: The role of shunting and patching during carotid endarterectomy remains controversial. METHODS: This is a retrospective case series evaluating consecutive patients undergoing carotid endarterectomy with routine shunting and patching. The primary endpoints were perioperative stroke, arterial injury, and lesion recurrence by duplex. RESULTS: Of the 220 operations performed, 43% were for symptomatic disease. Successful shunt placement occurred in 98%, with no shunt-related injuries. There was 1 minor perioperative stroke and no major strokes. At a mean follow-up of 24 months (median ⫽ 12 months), there was 1 restenosis potentially related to shunt placement. The incidence of asymptomatic ⬎50% stenosis in the patched segment was 8%. CONCLUSIONS: A combined policy of routine shunting and patching simplifies intraoperative decision making with results that rival or exceed those of trials in which their use was not standardized. Shunts need not be avoided because of concern of arterial injury. © 2012 Elsevier Inc. All rights reserved.
Carotid endarterectomy is an effective means of stroke prevention in patients with high-grade symptomatic (⬎70%) or asymptomatic (⬎60%) internal carotid artery stenosis and has been proven to be superior to medical management alone.1,2 Shunt placement preserves ipsilateral cerebral perfusion during the period of carotid clamping and may decrease the incidence of perioperative stroke because Presented at the North Pacific Surgical Association Annual Meeting, Vancouver, BC, Canada, November 11–12, 2011. * Corresponding author. Tel.: ⫹1-503-494-7593; fax: ⫹1-503-4944324. E-mail address: [email protected] Manuscript received October 18, 2011; revised manuscript December 21, 2011
0002-9610/$ - see front matter © 2012 Elsevier Inc. All rights reserved. doi:10.1016/j.amjsurg.2011.12.005
of cerebral hypoperfusion. Despite numerous investigations into the safety and efficacy of carotid shunting, its role remains controversial.3,4 There are essentially 3 approaches to carotid shunting: routine shunt placement, selective shunt placement, and routine nonshunting. Advocates of routine shunting suggest that this practice promotes technical proficiency and avoids the excess time, inconvenience, and cost associated with neuromonitoring techniques often used for selective shunt placement. Alternately, proponents of selective shunting argue that although it may decrease the risk of perioperative stroke, shunt placement is only truly necessary in a small percentage of patients and that routine shunting may lead to unnecessary shunt placement in as many as 85% of patients.5 It can also be argued that shunt
614
The American Journal of Surgery, Vol 203, No 5, May 2012
placement itself can lead to complications, including air or atheromatous emboli, arterial dissection, and acute arterial occlusion.6 In addition, despite data indicating a decreased risk of perioperative arterial occlusion as well as a decreased risk of subsequent restenosis,7 carotid patch angioplasty is not universally used in carotid endarterectomy. In our practice, we have for many years had a policy of routine shunt placement with patch arteriotomy closure. Thus, in this study, we sought to review operative and ultrasound records to quantify shunt-related arterial injury and evaluate a policy of routine shunt placement and patch closure during carotid endarterectomy.
Sundt-type shunts (Integra Neurosciences, Plainsboro, NJ) were used in 72% of cases (n ⫽ 158) and Pruitt-Inahara (LeMaitre Vascular, Burlington, MA) in 19% (n ⫽ 42). In 1 case, the shunt type was not specified, and in another an Argyle shunt (Covidien, Mansfield, MA) was used. In the remaining 18 cases, no shunt was ultimately used. Difficulty with shunt placement was noted in only 5 patients (2%). In 2 cases, the internal carotid artery was too small to accommodate the shunt, whereas a third was noted to have an exceedingly tortuous common carotid artery. There was 1 case in which the shunt could only be inserted 1 to 2 cm into the distal internal carotid artery, and, despite forward flow through the shunt, it could not be kept in place through the completion of patch closure as planned. Finally, there was 1 instance in which flow within the shunt could not be detected by Doppler despite the successful insertion of 2 different types of shunt. When a deliberate decision to skip shunt placement was made, it was based on a mean internal carotid artery stump pressure ⬎50 mm in 11 of 13 cases. In the 2 additional cases, the operation was performed under cervical block anesthesia, and neurologic status was preserved during the period of carotid cross-clamping. No injuries related to shunt placement were observed. Patch closure was used in 205 operations (93%). The most commonly used patch types were polyester (64%, n ⫽ 141) and bovine pericardium (26%, n ⫽ 58). The remainder of cases used saphenous vein (4%), polytetrafluoroethylene (1%), or no patch at all (7%). Primary closure was reserved for instances in which the operating surgeon noted the native arteries to be of a particularly large diameter. The mean follow-up was approximately 24 months (median ⫽ 12 months). Information regarding the postoperative course was available in 176 patients. There were 3 perioperative transient ischemic attacks (2%) noted and 1 minor perioperative stroke (1%) that manifested as a transient facial droop 1 month after surgery. There were no major strokes. In addition, there were 7 transient cranial nerve injuries (4%); these typically manifest as facial numbness. The availability of vascular laboratory data before 2004 was very limited, and, as a result, follow-up carotid duplex data were only available for 115 patients (52%) (Table 1). Of the 105 patients with no vascular laboratory data available, 74 (71%) did have continued vascular surgery clinic follow-up. Of the available studies, there were 12 patients with increased peak systolic velocities in either the proximal common carotid or distal internal carotid, which could be interpreted as a shunt-related event. However, a meticulous case review revealed normalized velocities on subsequent follow-up studies in 4 patients. In 4 others, globally elevated peak systolic velocities were attributed to a contralateral occlusion rather than an ipsilateral restenosis; 2 of these patients subsequently had normalized duplex findings. Two additional patients showed no evidence of stenosis on Bmode ultrasonography. Finally, 1 patient had elevated proximal common carotid artery velocities both pre- and post-
Methods The study was a retrospective review of a prospectively maintained database at an academic medical center. Intraand postoperative data were evaluated for consecutive patients undergoing carotid endarterectomy during the period beginning in January 2000 and ending in June 2010. Basic demographic information and comorbidities were recorded. Operative data included shunt placement, the type of shunt used, whether difficulty was encountered with shunt placement, and the type of patch used for arteriotomy closure. Postoperative complications including stroke, cranial nerve injury, and wound healing were reviewed and recorded. Results of arterial duplex ultrasonography from pre- and postoperative periods were evaluated for evidence of restenosis at the site of shunt placement (ie, the common carotid artery proximal to the site of the endarterectomy or the internal carotid artery distal to the site of endarterectomy) and within the patched segment (primarily the proximal and midcervical internal carotid artery). The primary endpoints were perioperative stroke, arterial injury, and lesion recurrence as assessed by arterial duplex ultrasound. The vast majority of operations were performed under general anesthesia. After the administration of systemic heparin, the internal, external, and common carotid arteries are sequentially clamped. The shunt is inserted into the distal internal carotid artery, allowed to back bleed, and then inserted proximally into the common carotid artery. Flow is confirmed within the shunt by continuous-wave Doppler. Once the endarterectomy is complete, the arteriotomy is routinely closed with a patch. After surgery, patients were advised to undergo a follow-up duplex evaluation in the early postoperative period and every 6 months thereafter.
Results Over the selected time period, 220 procedures were performed: 43% for symptomatic disease (n ⫽ 95) and 57% for asymptomatic disease (n ⫽ 125). Shunt placement was attempted in 207 cases (94% of total carotid endarterectomy) and was successful in 202 (98% of those attempted).
M.R. Kret et al. Table 1
Routine shunting during carotid endarterectomy
615
Average peak systolic velocities (cm/s) Peak systolic velocity (mean ⫾ standard deviation) Proximal common carotid artery
Preop (n ⫽ 106) 0–3 mo postop (n ⫽ 72) 3–12 mo postop (n ⫽ 61) 1–2 y postop (n ⫽ 62) ⬎2 y postop (n ⫽ 52)
88 95 92 93 93
⫾ ⫾ ⫾ ⫾ ⫾
24 31 21 31 23
Distal common carotid artery 87 102 100 96 99
⫾ ⫾ ⫾ ⫾ ⫾
73 43 44 39 50
Proximal internal carotid artery 419 85 98 90 90
⫾ ⫾ ⫾ ⫾ ⫾
143 45 42 39 39
Distal internal carotid artery 94 92 98 90 88
⫾ ⫾ ⫾ ⫾ ⫾
31 38 26 23 24
Preop ⫽ preoperative; postop ⫽ postoperative.
operatively because of a large proximal plaque burden and was thus not felt to have a restenosis attributable to shunt placement. There was 1 patient with persistent, mildly elevated velocities in the distal internal carotid; a review of the computed tomography scan of her neck obtained for an unrelated issue did suggest a narrowing in this segment. This patient did not develop symptoms related to the lesion during the follow-up period. In total, there were 17 patients who exhibited elevated velocities in the proximal internal carotid artery over the study period. After reviewing each of these cases, the incidence of asymptomatic ⬎50% stenosis in the patched portion was determined to be 8% (n ⫽ 9). Follow-up studies ultimately showed normal velocities in this segment in 6 patients, and in another no evidence of stenosis was seen on B-mode imaging. In 1 case, a pseudoaneurysm developed at the distal, posterior aspect of the patch several years after the original operation. This patient eventually underwent revision using a greater saphenous vein interposition graft. The notable recurrences include 1 early asymptomatic recurrence associated with a focal stenosis that was treated with a carotid stent. In addition, there was 1 instance in which complete ipsilateral carotid occlusion was discovered 8 years after the original operation. This patient had a single postoperative follow-up visit with vascular surgery and was subsequently seen regularly by her primary care provider only. The occlusion was noted after she presented to her primary care provider with syncope.
Comments This series shows the safety and efficacy of routine carotid shunting with patch arteriotomy closure during carotid endarterectomy. The low incidence of perioperative stroke in our series despite the high proportion of symptomatic patients compared with most single-institution series suggests that carotid shunting combined with patch arteriotomy closure is an effective means to prevent harmful neurologic effects that result from a lack of cerebral perfusion. These data are in line with published data on routine shunt and patch use during carotid endarterectomy. A recent
review examining the use of shunts in carotid endarterectomy cited a perioperative stroke rate of 1.4% for routine shunting based on the pooled results of 14 previous studies.4 Bellosta et al8 used a similar strategy of routine shunt placement with patch closure and reported a perioperative stroke rate of .7% and asymptomatic ⬎50% restenosis in 1.7% over a mean follow-up interval of 24 months. In our series, 9 patients (8%) had evidence of restenosis in the patched segment although only 1 required subsequent reintervention. Despite numerous reports showing the safety of routine shunting during carotid endarterectomy, this approach remains controversial. The 2009 update of the Cochrane Review3 of routine versus selective shunting during carotid endarterectomy concluded not only that evidence remained insufficient to support or refute the use of carotid shunting but also that no single method for neurologic monitoring in selective shunting has proved superior. Recently, AbuRahma et al5 compared routine versus selective shunt placement in 200 prospectively randomized patients. Perioperative stroke rates were 2% and 3%, respectively, a difference that did not reach significance. This led the authors to conclude that the decision to shunt routinely or selectively should be based on the surgeon’s level of comfort with either technique. Most would agree that carotid endarterectomy performed on an awake patient under cervical block anesthesia provides the most reliable method to assess neurologic function.9 –11 However, this approach can be compromised by patient anxiety or claustrophobia, limitations on positioning because of neck fixation, and more complicated dissections required in reoperative fields. Furthermore, shunting based on the development of neurologic symptoms results in the need for urgent shunt placement, which can be much more anxiety provoking and less controlled than elective shunting immediately after carotid cross-clamping. When general anesthesia is used, some form of adjunctive testing must be used to determine whether a shunt should be placed. Two of the more common approaches used are measurement of internal carotid artery stump pressure and electroencephalographic (EEG) monitoring. In our series, mean carotid stump pressures ⬎50 mm Hg were cited as evidence of
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The American Journal of Surgery, Vol 203, No 5, May 2012
preserved cerebral perfusion in 11 patients. This has generally been considered a safe threshold, and none of the patients in our series suffered a perioperative neurologic event. Establishing safe, consistent threshold parameters for shunt placement has proven difficult. In multiple studies, carotid stump pressure ⬎50 mm Hg has been shown to identify 96% to 97% of patients with concurrent EEG changes.12,13 Despite these findings, Harada et al13 argued that the sensitivity and specificity for this threshold stump pressure (89% and 61%, respectively) were suboptimal for use as a standalone test to determine whether or not to shunt. Despite low rates of perioperative stroke, neurologic monitoring with selective shunting only approximates the risk of cerebral malperfusion. As shown by those studies performed in awake patients, a small percentage will suffer from cerebral ischemia despite normal EEG tracings and carotid stump pressure. Hans and Jareunpoon11 compared these measures in operations performed under cervical block anesthesia. Beyond the threshold stump pressure of 50 mm Hg, only 1.4% of patients required shunting based on changes in neuroexamination. Interestingly, of those that required shunts, only 40.6% showed ischemic changes on the electroencephalogram. Thus, the authors concluded that awake neurologic monitoring is the most sensitive indicator of the need for carotid shunt. Critics of routine shunting argue that this approach unnecessarily exposes a large number of patients to the risks of shunting. Frawley et al6 analyzed a series of 259 consecutive carotid endarterectomy using intraoperative thiopental for neuroprotection and documented a perioperative stroke rate of 1.7%. Although EEG changes occurred with carotid artery clamping in nearly 20% of patients, no strokes occurred in these patients. Thus, the authors argued that a certain number of strokes will occur despite all efforts at prevention and that thiopental cerebral protection eliminates strokes caused by complications of shunt placement. Similarly, Samson et al14 published a series of 654 carotid endarterectomies performed without a shunt leading to a 3% incidence of stroke or a TIA. Although they acknowledge that in patients with minimal internal carotid artery back bleeding, shunts may offer the potential to decrease the risk of stroke, they counter that these patients would then be subject to the risks of carotid artery shunting. Although the inherent risks remain 1 of the major arguments against routine carotid shunting, these were not observed in our series. In 202 patients in whom shunt placement was attempted, no instances of arterial dissection, distal embolization, or vessel occlusion were noted. There were 12 patients who had elevated peak systolic velocities in the proximal common or distal internal carotid artery on at least 1 follow-up duplex scan. Although elevated velocities in these locations raise the possibility of a shunt-associated lesion, after reviewing each of these cases, only one appeared to have an actual stenosis with a potential relationship to shunt placement. Among those with elevated veloc-
ities deemed not to have a true stenosis, 2 trends emerged. First, many of the elevated velocities normalized on subsequent imaging studies. In others, the velocity increases were observed in the presence of a contralateral occlusion. The phenomenon of increased blood flow velocities opposite a contralateral occlusion has been recognized in multiple previous studies evaluating duplex parameters of carotid stenosis.15,16 As a result, these findings were interpreted as normal in our analysis. Ultimately, our results indicate that essentially no immediate complications and very few, if any, harmful long-term sequelae result from shunt placement. We believe that the routine combination of shunting and patching simplifies intraoperative decision making with results that rival or exceed those of trials in which their use was not standardized. In addition, routine shunting avoids the excess cost associated with an electroencephalogram or other neurologic monitoring techniques. Furthermore, this strategy can improve surgeons’ familiarity and facility with shunt placement, particularly when trainees are involved in these operations. Shunts need not be avoided because of the concern for arterial injury.
References 1. Executive Committee for the Asymptomatic Carotid Atherosclerosis Study. Endarterectomy for asymptomatic carotid artery stenosis. JAMA 1995;273:1421– 8. 2. North American Symptomatic Carotid Endarterectomy Trial Collaborators. Beneficial effect of carotid endarterectomy in symptomatic patients with high-grade carotid stenosis. N. Engl. J. Med. 1991;325: 445–53. 3. Rerkasem K, Rothwell PM. Routine or selective carotid artery shunting for carotid endarterectomy (and different methods of monitoring in selective shunting). Cochrane Database Syst Rev 2009;4:CD000190. 4. AbuRahma AF, Mousa AY, Stone PA. Shunting during carotid endarterectomy. J Vasc Surg 2011;54:1502–10. 5. AbuRahma AF, Stone PA, Hass SM, et al. Prospective randomized trial of routine versus selective shunting in carotid endarterectomy based on stump pressure. J Vasc Surg 2010;51:1133– 8. 6. Frawley JE, Hicks RG, Gray LJ, et al. Carotid endarterectomy without a shunt for symptomatic lesions associated with contralateral severe stenosis or occlusion. J Vasc Surg 1996;23:421–7. 7. Rerkasem K, Rothwell PM. Patch angioplasty versus primary closure for carotid endarterectomy. Cochrane Database Syst Rev 2009;4; CD000160. 8. Bellosta R, Luzzani L, Carugati C, et al. Routine shunting is a safe and reliable method of cerebral protection during carotid endarterectomy. Ann Vasc Surg 2006;20:482–7. 9. Calligaro KD, Dougherty MJ. Correlation of carotid artery stump pressure and neurologic changes during 474 carotid endarterectomies performed in awake patients. J Vasc Surg 2005;42:684 –9. 10. McCarthy RJ, McCabe AE, Walker R, et al. The value of transcranial Doppler in predicting cerebral ischaemia during carotid endarterectomy. Eur J Vasc Endovasc Surg 2001;21:408 –12. 11. Hans SS, Jareunpoon O. Prospective evaluation of electroencephalography, carotid artery stump pressure, and neurologic changes during 314 consecutive carotid endarterectomies performed in awake patients. J Vasc Surg 2007;45:511–5. 12. Cherry KJ, Roland CF, Hallett JW, et al. Stump pressure, the contralateral carotid artery, and electroencephalographic changes. Am J Surg 1991;162:185–9.
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13. Harada RN, Camerota AJ, Good GM, et al. Stump pressure, electroencephalographic changes and the contralateral carotid artery: another look at selective shunting. Am J Surg 1995;170:148 –53. 14. Samson RH, Showalter DP, Yunis JP. Routine carotid endarterectomy without a shunt, even in the presence of contralateral occlusion. Cardiovasc Surg 1998;6:475– 84. 15. Fujitani RM, Mills JL, Wang LM, et al. The effect of unilateral internal carotid occlusion upon contralateral duplex study: criteria for accurate interpretation. J Vasc Surg 1992;16:459 – 68. 16. AbuRahma AF, Richmond BK, Robinson PA, et al. Effect of contralateral severe stenosis or carotid occlusion on duplex criteria of ipsilateral stenoses: comparative study of various duplex parameters. J Vasc Surg 1995;22:751– 62.
Discussion Dr Ravindar Sidhu (Vancouver, BC, Canada): There are multiple strategies for cerebral protection and moni-
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toring during carotid endarterectomy. The literature does not support the use of 1 method over another. Endarterectomy under local anesthesia provides optimal neurologic monitoring. However, if a shunt is required, patient movement and stability become significant issues. With other forms of monitoring such as an electroencephalogram, stump pressure measurements, and transcranial Doppler, shunt rates are about 15%. Routine shunting eliminates the need for monitoring but may cause unnecessary vascular trauma. In my practice, another important reason for shunting is to provide trainees with experience in shunt placement. The bottom line is that, irrespective of the method of cerebral protection, acceptable stroke and mortality rates must be attained (3% for asymptomatic and 6% for symptomatic carotid stenoses). The authors showed that their approach is indeed acceptable.