Neurology India Medknow Publications on behalf of the Neurological Society of India ISSN: 0028-3886 EISSN: 1998-4022 Vol. 59, Num. 3, 2011, pp. 390-396

Neurology India, Vol. 59, No. 3, May-June, 2011, pp. 390-396

Topic of the Issue: Original Article

Carotid endarterectomy: Results and long-term follow-up of a single institution

Basant K Misra¹, Harshad R Purandare¹, Rahul Ved¹, PP Ashok²

¹ Department of Neurosurgery, Gamma Knife Radiosurgery, P. D. Hinduja National Hospital and Medical Research Centre, Mumbai, India
² Department of Neurology, P. D. Hinduja National Hospital and Medical Research Centre, Mumbai, India

Correspondence Address: Basant K Misra Department of Neurosurgery and Gamma Knife Radiosurgery, P. D. Hinduja National Hospital and Medical Research Centre, Veer Savarkar Marg, Mahim, Mumbai - 400 016 India basantkmisra@gmail.com

Date of Submission: 13-Sep-2010
Date of Decision: 19-Oct-2010
Date of Acceptance: 07-Dec-2010

Code Number: ni11115

PMID: 21743168

DOI: 10.4103/0028-3886.82746

Abstract

Keywords: Carotid artery disease, carotid artery stenosis, carotid endarterectomy, stroke, transient ischemic attack

Introduction

There has been an increase in the burden of stroke in India in the last few decades. In India the reported average annual incidence (145/100,000 populations) and 30-day mortality (41%) are both high when compared to the developed nations. ^[1],[2] Carotid atherosclerotic disease accounts for 20% of cerebral ischemic events. ^[2],[3] Carotid endarterectomy (CEA) is superior to best medical management for symptomatic severe carotid stenosis in preventing stroke and death. ^[3],[4] One-third of the patients with carotid-related stroke die or have a severe disability at one year of the ictus. ^[5] The best medical therapy achieves an absolute risk reduction (ARR) of 17−25%. ^[6] There is very little data on the experience of the neuroscientists of India regarding CEA. We present our experience and outcomes with CEA in symptomatic carotid disease.

Material and Methods

We retrospectively reviewed the case records and hospital database of 49 consecutive patients who underwent CEA over a 10-year period (May 2000-December 2009) at our institute. Demographic details, clinical findings, imaging data and perioperative protocol were evaluated. Perioperative complications and follow-up outcomes were analyzed for patients operated till December 2009, having a minimum of six months postoperative follow-up.

Preoperative evaluation

Diagnostic preoperative evaluation included a neck vessel Doppler and computed tomography angiography (CTA) and/or magnetic resonance angiography (MRA) [Figure - 1]. In the initial part of the series, patients underwent digital subtraction angiography (DSA) as a routine evaluation. A thorough medical and detailed cardiology evaluation was carried out for all patients. Patients also underwent evaluation for prothrombotic disorders. Medical therapy for comorbidities such as hypertension, diabetes mellitus and dyslipidemia was optimized.

Perioperative protocol

Antiplatelet medications were continued and not stopped at any time during the perioperative period. We performed all cases under general anesthesia. Cerebral protection was achieved using propofol infusion and mild hypothermia (33−34°C). All procedures were done with continuous electroencephalogram (EEG) monitoring. A temporary bypass via intraluminal shunt was introduced using a 6 cm long 8 french (FR) infant feeding tube in cases with EEG slowing. Injection heparin 100 IU/kg were administered before carotid clamping.

The utmost important step was to have an adequate exposure of the carotid vessels, particularly the internal carotid artery (ICA) and control distal to the plaque, before opening the vessel. The ICA was occluded first, to prevent embolization, with temporary aneurysm clip. The common carotid artery (CCA) and external carotid artery (ECA) were then occluded with snuggers and the superior thyroid artery with a mini temporary aneurysm clip. The arteriotomy was started in the CCA and extended to ICA till normal lumen was reached. Then the plaque dissection was done under a higher magnification After gross plaque removal, the lumen was irrigated with heparinized saline and all loose fragments were removed. Densely adherent intimal flap was tagged down using 6-0 prolene sutures tied on the externa. After plaque excision, primary closure was done using 6-0 prolene continuous sutures from either corner. The final closure in the center of the arteriotomy was done after temporarily sequentially bleeding the ECA, the ICA and finally, the CCA to flush out any clot and debris. The flow in the carotid system was re-established by opening up the vessels in the following order: ECA followed by the CCA and finally, the ICA after a gap of 10−15 s. Heparin was not reversed and patient was extubated on the table. Blood pressure was strictly controlled during the entire procedure. Induced hypertension (20% above the baseline) was achieved for the period of carotid clamping. Normotension was maintained in the postoperative period.

After discharge, a detailed neurological evaluation was done on outpatient basis. Preferred follow up imaging were CTA/Doppler examination [Figure - 1]. Antiplatelet agents and medical management for other comorbidities was continued as required.

Results

The series included 53 CEA (right 26 and left 27) procedures performed in 49 [39 males and 10 females, mean age 62.72 years (range 32-83 years)] consecutive patients [Table - 1]. Seventeen patients (34.7%) presented with TIA and the remaining 32 patients (65.3%) had an anterior circulation stroke. The mean time to perform CEA after stroke/TIA was 32 days (range: 6−65 days). None of the patients were operated for stroke in evolution.

The mean stenosis on the operated side was 83% (range: 70−99%) by the North American Symptomatic Carotid Endarterectomy Trial (NASCET) criteria. Contralateral ICA stenosis was seen in 21 patients (42.85%); 4 patients had 100% occlusion, 3 patients had stenosis more than 70% and have subsequently undergone contralateral surgery while, the remaining 14 patients had moderate stenosis of ≤50% and were clinically followed up with appropriate medical management. None of these patients had worsening of the degree of narrowing or clinical manifestations. Thus three patients underwent staged bilateral surgery while one patient underwent a redo surgery for restenosis. Associated comorbidities are listed in [Table - 2]. One patient with bilateral carotid disease underwent simultaneous CABG with left CEA in December 2005 followed by right CEA in March 2006. One patient underwent percutaneous transluminal coronary angioplasty (PTCA) with left anterior descending artery stenting, four days prior to CEA.

Primary suturing was done in 52 procedures. The redo CEA patient underwent a saphenous venous patch graft. The first surgery was done at the same center in August 2007 while the redo was done in May 2009. The surgery was uneventful and the patient was asymptomatic, however, follow-up Doppler and CTA showed 70% stenosis just proximal to the site of endarterectomy. The redo surgery was carried out uneventfully. Intraoperative shunting was performed in three patients as the intra-operative EEG monitoring showed slowing. Two more patients had minimal transient EEG changes which stabilized and did not merit the shunt placement. Our occlusion time in the initial period of the study was approximately 45-60 minutes, while at present the average occlusion time ranges between 20 and 30 min.

Complications

One patient developed hemodynamic instability secondary to myocardial infarction on the operating table prior to carotid manipulation and died. Three other patients developed transient hemodynamic instability in the perioperative period without consequences. Two patients developed transient hemiparesis with aphasia. They had a normal CT brain and neck vessel. Doppler showed a normal caliber with no thrombus [Table - 3]. One patient developed a contralateral faciobrachial stroke within 6 h of surgery. Neck vessel Doppler showed an intraluminal thrombus at the operative site. He underwent immediate re-exploration with clot evacuation. He received low molecular weight heparin (LMWH) and the deficit improved to Medical Research Council (MRC) grade 3/5 power at discharge, and has been static on follow-up. One patient had persistent TIA episodes. Carotid evaluation was normal. He is symptom-free on medical management. One patient developed twelfth-cranial nerve paresis on the side of surgery. Thus the overall complication rate (mortality, major and minor neurological and procedural morbidity) is 11.34%.

Follow-up Doppler was performed in 36 patients and CTA was performed in the remaining 10 patients. On long-term follow-up, only the patient who underwent redo surgery was detected to have a restenosis. This patient was asymptomatic. No fresh ischemic episodes were noted in other patients.

Thus our perioperative mortality rate was 1.89%, perioperative stroke rate was 1.89% and transient neurological dysfunction without any ischemic insult or stroke occurred in 3.77% [Table - 3]. Our mean follow-up was 4.6 ± 0.9 years (range 0.6−8.9 years).

Discussion

Three major trials, NASCET, European Carotid Surgery Trial (ECST), and the Veterans Administration Symptomatic Stenosis Trial (VASST), addressed the issue of CEA symptomatic carotid stenosis. The VASST trial was terminated early after the interim analysis of the NASCET, and ECST trials. The NASCET data showed an ARR of 17±3.5% for stroke at two months and ARR for any stroke or death at two years at 12.7% over and above optimum medical management. The corresponding figures for ECST were 18.6% at one month and 11.6% at three years. ^[3],[4] A meta-analysis as well as re-analysis of the pooled raw data of 6092 patients, with 35000 patient-years of follow-up in these randomized trials confirmed the significant benefit of surgery in the severe ICA stenosis group by the NASCET criteria (≥70% stenosis) and moderate benefit in symptomatic stenosis of 50−69%. ^[7],[8] Ideally, the procedure should be done within two weeks of the event. ^[9] We could not strictly adhere to this protocol, predominantly due to delayed referral. The advantage of CEA is based on the achievement of low procedural complication rate, a perioperative composite stroke, MI and death rate of less than 3% in asymptomatic group and less than 6% in symptomatic group, thus improving on the natural history of the disease. ^[10] Our results justify our choice and indications of CEA.

While a majority of vascular surgeons perform closure using a patch, many neurovascular surgeons do not. DeSousa and Silva Costa reported a series of more than 3000 cases with primary closure with excellent results. ^[11] A large number of even the most recent randomized trials including the Carotid Revascularization Endarterectomy versus Stenting Trial (CREST) and the International Carotid Stenting Study (ICSS) permitted either modes of closure. Recent Cochrane database meta-analysis did not find any statistically significant difference in perioperative stroke and mortality rate between the two groups. ^[12] In our study temporary shunt placement was needed in only three patients. We used a 6 cm long 8 FR infant feeding tube for the purpose of shunting instead of a patented reusable shunt mainly to reduce the cost to the patient. Incidentally, we found a similar use of feeding tube even in USA. ^[13]

Fluctuation of blood pressure in the per-operative and post-operative period is regarded as one of the most significant factors responsible for neurological morbidity including carotid hyper perfusion syndrome. ^[14] We advocate a period of induced hypertension in the period of carotid clamping, followed by controlled normotension at the upper limit of normal range to prevent such an event.

The reported frequency of cranial nerve injury following CEA ranges from 3 to 23% though there have been only a few series where patients were routinely examined before and after surgery by a neurologist, as has been done in our series. Most studies comparing surgical versus endovascular management have emphasized on the low cranial nerve morbidity of the latter approach as an additional advantage over surgery. However, a study which reviewed patients in the ECST trial, which is the largest series with a neurological review on follow-up, concluded that 5.1% patients had an immediate deficit, 3.7% had a deficit on discharge and only 0.5% had a persistent deficit on four month follow-up. Duration of surgery for more than 2 h has been regarded as a significant factor. ^[15] We had only one case of temporary dysfunction of the twelfth nerve in our series. Nevertheless, the risk of cranial nerve injury should be communicated to patients.

Numerous groups advocate CEA under local anesthesia to permit neurological monitoring and reduce the incidence of postoperative cognitive deficits. The General Anesthesia versus Local Anesthesia (GALA) trial, a multicentric randomized controlled trial enrolling 3526 patients found a comparable rate of stroke and myocardial infarction after surgery in both the groups (4.8% in GA and 4.5% in LA). Neither was there any difference in outcome for quality of life or length of hospital stay. ^[16] We have performed all procedures under general anesthesia and had transient cognitive problems in 3.77% cases only. General anesthesia permits better control of blood pressure, neurophysiologic monitoring and minimizes patient anxiety related to the procedure, in addition to improving the comfort level of the surgical team.

Carotid artery stenting (CAS) has been suggested as a minimally invasive alternative to CEA. Numerous studies, predominantly single institute reviews have demonstrated comparable results. However, even large studies, such as the Carotid Revascularization using Endarterectomy or Stenting Systems (CaRESS) are non-randomized or have a significant percentage of asymptomatic patient. ^[17] In many studies, the surgical results in the control arm is poorer than those recommended by consensus guidelines, introducing an analytical bias in favor of CAS. A recently published meta-analysis of the 11 randomized control trials, comparing CEA with CAS, noted that the weighted average incidence of periprocedural death or stroke was 5.4% (95% confidence interval 4−7%) for CEA and 7.3% (4.9−10.1%) for CAS. CEA was associated with better periprocedural outcomes than CAS. Conversely, the risk of neuropathy and periprocedural myocardial infarction was higher with CEA. In the intermediate-to-long term, primary or secondary end points did not differ significantly, suggesting similar efficacy of the two procedures in the more recent studies. ^[18] The Endarterectomy Versus Angioplasty in Patients with Symptomatic Severe Carotid Stenosis (EVA-3S) trial was prematurely aborted after recruiting 527 patients because of significant advantage of CEA over CAS. The 30-day incidence of any stroke or death was 3.9% after CEA and 9.6% after stenting, while the same figures at six months stood at 6.1% and 11.7%, respectively. ^[19],[20] The current recommendation is to use an FDA-approved stent with distal embolizing protection device (EPD). However, the interim results of the International Carotid Stenting Study (ICSS), with 1713 patients (stenting group, n = 855; endarterectomy group, n = 858), showed a stroke, death or procedural MI rate of 8.5% in the CAS group compared with 5.2% in the CEA group. ^[21] Also, there was three times more incidence of new ischemic lesions on diffusion weighted imaging (DWI) on post-treatment scans of patients undergoing CAS, suggesting that protection devices seemed to be ineffective in preventing cerebral ischemia during stenting. ^[22] It is recommended that CEA should remain the choice of treatment for patients suitable for surgery. A similar view was echoed by the long-term results of the Carotid and Vertebral Artery Transluminal Angioplasty Study (CAVATAS), which observed that severe carotid restenosis (≥70%) occurred significantly more often in patients in the endovascular arm than in patients in the endarterectomy arm with an estimated five-year incidence of restenosis being 30.7% and 10.5%, respectively. ^[23]

The Carotid Revascularization Endarterectomy versus Stenting Trial (CREST) is the largest randomized trial with blinded end point adjudication to date. In CREST, 2502 patients with symptomatic or asymptomatic carotid stenosis were randomised to undergo CAS or CEA. The primary composite end point was stroke, myocardial infarction, or death from any cause during the periprocedural period or any ipsilateral stroke within 4 years after randomization. In the median follow-up period of 2.5 years, there was no significant difference in the estimated 4-year rates of the primary end point between the stenting group and the endarterectomy group (7.2% and 6.8%, respectively). The estimated 4-year rate of stroke or death was 6.4% with CAS and 4.7% with CEA. During the periprocedural period, there was a higher risk of stroke with CAS and a higher risk of myocardial infarction with CEA, neither being statistically significant. The investigators concluded that CAS and CEA were associated with similar rates of primary composite outcome- periprocedural stroke, myocardial infarction, or death and subsequent ipsilateral stroke- among men and women with either symptomatic or asymptomatic carotid artery stenosis. On critical review of the CREST data, it is evident that nearly half the patients included in the trial had asymptomatic carotid artery stenosis. When we consider the symptomatic carotid stenosis patients separately, the subject of our discussion, the rate of stroke or death in CAS group was almost double (6.0%) of that in the CEA (3.2%) group in the CREST. The authors also mention that the quality of life among survivors at 1 year in the CREST was worse in CAS patients complicated with stroke than the CEA patients suffering from periprocedural myocardial infarction. ^[24],[25]

A single institution review in the American subcontinent showed that the mean procedural cost for CAS ($7543.61 ± $2886.54) was significantly higher than that for CEA ($2720.00 ± $926.38, P < 0.001). ^[26] This factor has a significant impact and should be given due consideration especially in our subcontinent. Finally, there are stringent restrictions for insurance cover for CAS with EPD outside United States Food and Drug Administration (USFDA) approved trials. Currently, coverage is provided only for symptomatic stenosis ≥ 70% verified by angiography in patients who are at high risk for surgery. Only Center for Medicare Services (CMS)-approved carotid stenting facilities with recorded data on carotid stenting cases performed and a clear program for physician credentialing are covered. ^[27]

Proper patient selection will go a long way in achieving satisfactory outcomes with CEA. Our policy of thorough pre operative cardiac evaluation by a cardiologist and referring high risk cardiac patients for CAS has also helped us reduce our periprocedural myocardial infarction rate. While the expertise and infrastructure to perform proper CAS is still not available in many centers across the country, there is no capital investment necessary for performing a CEA, a simple procedure with class I evidence of its superiority against all other forms of management.

This endeavor is an attempt to document our results of CEA in an effort to popularize CEA and justify its use in properly selected patient population. In line with the FDA and American Heart Association (AHA) guidelines, we recommend CAS only for patients unsuitable or high risk for surgery including those with severe coronary disease, recent MI or unstable angina, Left ventricular ejection fraction (LVEF) ≤30% who are poor candidate for GA, cases with technical difficulty - high bifurcation with short neck, post-endarterectomy restenosis, patients with radical neck dissection or post-radiation and tandem siphon stenosis.

Conclusion

Stroke due to carotid atherosclerotic disease is a preventable entity with significant risk reduction achieved by optimum combination of medical and surgical management. CEA is among one of the few neurosurgical procedures with class I evidence of its superiority over the best medical management in patients with severe carotid stenosis. Detailed cardiac evaluation and management is mandatory to reduce perioperative risks. CAS is considered appropriate in high-risk patients only.

Most surgical series on CEA in India have been reported by cardiac and vascular surgeons. Our series is one of the largest reported neurosurgical series in this country. We have achieved surgical results and outcomes comparable to the international guidelines and recommendations for CEA. ^[7],[8],[10]

References

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