Staged bilateral carotid stenting, an effective strategy in high-risk patients – insights from a prospective multicenter trial

Article Outline

• Abstract
• Methods
  • Study design
  • Patient selection
  • Carotid stent procedure
  • Follow-up
  • Endpoint definitions
  • Statistical methods
• Results
  • Baseline and procedural characteristics
  • Clinical outcomes
  • Duplex ultrasound
• Discussion
  • Shortcomings
• Conclusions
• Author contributions
• References
• Copyright

Objective

To prospectively evaluate outcomes of high-risk patients undergoing bilateral carotid artery stenting (CAS).

Methods

A total of 747 patients at increased risk for carotid endarterectomy (CEA) were enrolled in a prospective registry at 47 US sites of the Boston Scientific EPI: A Carotid Stenting Trial for Risk Surgical Patients (BEACH) trial. Among them, 78 (10.4%) patients underwent contralateral CAS > 30 days after the primary CAS procedure. Patients were followed at 1, 6, and 12 months, and annually thereafter for 3 years. The primary endpoint was the cumulative incidence of non Q-wave myocardial infarction within 24 hours, periprocedural (≤30 days) death, stroke or Q-wave MI, and late ipsilateral stroke or death due to neurological events from 31 days up to 12 months. The bilateral patients are independent from the pivotal cohort.

Results

Mean follow-up was 885 + 320 days in the bilateral and 861 + 343 in the pivotal group. The primary endpoint occurred in 6.8% (5/73) of the bilateral patients and 8.9% (40/447) of the pivotal group (P = .66). There were no statistically significant differences between the bilateral and the pivotal groups with regard to any of the components of the primary or secondary endpoints. The univariate 1-year major adverse event (MAE) free survival was 93.6% and 91.6% in the bilateral and pivotal groups, respectively (P = .55). Multivariate logistic regression analysis with adjustment for various clinical baseline factors revealed no differences in the primary endpoint when comparing the bilateral with the pivotal groups at 30 days (odds ratio [OR]: 0.8673, 95% confidence interval [CI] 0.4590-1.6389, P = .66) or 1 year (OR: 0.9102, 95% CI 0.5503-1.5053, P = .73).

Conclusions

Bilateral carotid stenting is an effective treatment strategy in patients determined to be at high-risk for CEA with no increase in morbidity or mortality results extended out to one year in a prospective multicenter trial.

Large-scale randomized trials have demonstrated that carotid endarterectomy (CEA) is an effective treatment for the prevention of cerebrovascular events in patients with moderate to severe symptomatic¹, ² and asymptomatic³ carotid artery stenosis. Carotid artery stenting (CAS) with embolic protection is increasingly regarded a treatment alternative in patients with carotid artery stenosis at high surgical risk.⁴, ⁵, ⁶, ⁷ Bilateral carotid stenosis is encountered in up to 51% of patients undergoing CAS and its prevalence is expected to increase as life expectancy increases.⁶, ⁸, ⁹, ¹⁰ Despite encouraging single-center experiences,¹¹, ¹² patients with bilateral carotid artery disease are presumed at high risk for revascularization and have thus been excluded from most prospective trials. Therefore, data on the safety of bilateral CAS is currently scarce.

The purpose of the present study was to compare midterm results of high surgical risk patients undergoing bilateral carotid artery stenting to those undergoing unilateral treatment in a prospective, multicenter, single arm trial. Our hypothesis was that outcomes of patients undergoing staged bilateral CAS would be noninferior to those undergoing unilateral treatment.

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Methods 

Study design 

Between February 2002 and December 2003, 747 patients at increased risk for CEA were enrolled in the BEACH trial at 47 US centers. The trial was designed to evaluate the safety and efficacy of the Carotid Wallstent with the Filterwire EX/EZ cerebral protection system in patients with anatomic and/or comorbid conditions that placed them at high risk for adverse events with carotid endarterectomy. Enrolment was divided into two separate phases: the roll-in phase and the pivotal/bilateral phase. The bilateral subgroup was designed to be evaluated independent from the pivotal unilateral population. The protocol was approved by the Institutional Review Boards of all the participating centers and written informed consent was obtained from patients prior to enrolment. The trial complied with the Declaration of Helsinki and results are reported on the National Institutes of Health website (Clintrials.gov, Identifier NCT00316108). Investigator training included review of animal studies, on-site proctoring to achieve competence in device implantation, and general training on the protocol.

Patient selection 

Inclusion and exclusion criteria, description of CAS techniques and devices used as well as 30-day and 1-year results of the entire patient cohort are reported elsewhere.⁶, ⁷ Briefly, eligible patients with carotid disease were required to meet general criteria plus at least one definition of high-risk for surgery based on specific anatomic and comorbid clinical criteria to be included in the BEACH trial. The common carotid artery (CCA), carotid bifurcation, or internal carotid artery (ICA) had to be >4 mm and <9 mm in diameter, with ≥50% stenosis by angiography in symptomatic patients and ≥80% in asymptomatic patients as assessed by quantitative angiography using the North American Symptomatic Carotid Endarterectomy Trial (NASCET) methodology.²

Patients diagnosed with bilateral carotid artery disease requiring treatment for both ipsilateral and contralateral disease at the time of enrolment were entered in the BEACH bilateral registry. For inclusion in this registry, the ipsilateral lesion had to comply with all above-mentioned general inclusion and exclusion criteria that classified patients at high risk for surgery. The contralateral lesion was required to meet the inclusion criteria stenosis threshold for stroke prevention independent of the risk for surgery.

Both stent procedures were conducted in accordance with the BEACH trial protocol. The most symptomatic stenosed artery was treated first, identified as the primary lesion (also referred to as the ipsilateral lesion), whereas the second stent procedure was required to be staged and scheduled >30 days after the first target lesion procedure (referred to as the contralateral lesion). In patients where both lesions were asymptomatic and of similar degrees of stenosis, the carotid supplying the dominant hemisphere was treated first.

Carotid stent procedure 

Procedural details have previously been reported elsewhere.⁶, ⁷ Briefly, CAS was performed using the Carotid WALLSTENT and the FilterWire EX/EZ distal embolic protection system (Boston Scientific Corporation, Natick, Mass). Before stent placement, patients received aspirin (325 mg/day starting ≥72 hours before) plus a loading dose of clopidogrel (450 mg) if patients were previously not on clopidogrel. Ticlopidine (250 mg twice daily) was substituted in patients unable to tolerate clopidogrel. After sheath placement, heparin was administered and supplemented as needed to maintain an activated clotting time of ≥275 seconds or >200 seconds when a glycoprotein IIb/IIIa receptor inhibitor was administered. Glycoprotein IIb/IIIa receptor inhibitors were not mandated by protocol and were used at the operator's discretion. Following the procedure, patients received aspirin (325 mg daily) indefinitely and clopidogrel (75 mg daily) or ticlopidine (250 mg twice daily) for 30 days. For the bilateral registry group, both stenting procedures were conducted in accordance with this protocol.

Follow-up 

All patients were examined before (within 7 days) and after the procedure (per protocol, within 24 hours and at the time of any change in clinical symptoms) by an independent neurologist or neurosurgeon certified in the administration of the National Institutes of Health Stroke Scale (NIHSS). All patients underwent carotid duplex ultrasonography before the procedure and prior to discharge. Independent ultrasound and angiographic core laboratories provided review of all studies throughout the course of the trial and validation of site-determined entry criteria.⁶ Follow-up included carotid duplex ultrasonography as well as independent neurologic examination using the NIH stroke scale at 1, 6, and 12 months, and yearly thereafter through 5 years. Adverse events were adjudicated by an independent Clinical Events Committee.

Endpoint definitions 

The primary composite endpoint was non Q-wave myocardial infarction (MI) within 24 hours following CAS, periprocedural (≤30 days) death, stroke, or Q-wave MI and late ipsilateral stroke or death due to neurological events from 31 days up to 12 months follow-up.⁶, ⁷ Secondary solitary endpoints comprised death (neurologic, cardiac, and general), stroke (ipsilateral, contralateral, major and minor ischemic, and hemorrhagic) and Q-wave MI. Technical success was calculated based on the number of attempts to place the system (FilterWire plus WALLSTENT). Adverse events were adjudicated by an independent Clinical Events Committee. For the bilateral group, the late ipsilateral event was relative to the primary target lesion.

Stroke was defined as a new focal neurological deficit of presumed vascular origin persisting more than 24 hours, with a neuro-imaging study excluding a different etiology. It included patients presenting with clinical signs and symptoms suggestive of subarachnoid hemorrhage, intracerebral hemorrhage, or cerebral infarction. Strokes were categorized as ipsilateral or contralateral, periprocedural (≤30 days) or late (≥31 days from the procedure), and as major or minor. A major stroke was a stroke that was present after 7 days and increased the NIHSS of the patient by ≥4 points. A minor stroke was a stroke that resolved completely within 7 days or increased the NIHSS of the patient by ≤3 points. A transient ischemic attack was a focal ischemic neurological deficit of abrupt onset and of presumed vascular etiology that resolved completely within 24 hours of onset.

Definitions for MI included Q-wave and non Q-wave infarctions. A Q-wave MI was required to have pathologic Q-waves not present on a previous electrocardiogram (ECG) in two or more contiguous leads (as determined by the ECG core laboratory, Harvard Clinical Research Institute, Boston, Mass). A non Q-wave MI had no new pathologic Q-waves on ECG and a total creatinine kinase of greater than two times the normal with an elevated MB fraction.

Technical failure was defined as 30% residual stenosis. Postprocedural restenosis was defined as a ≥70% stenosis by duplex ultrasound and assumed in case of presence of peak systolic velocity ≥350 cm/s and an internal carotid artery to common carotid artery ratio ≥4.75.¹³, ¹⁴ Target lesion revascularization was at the discretion of the treating physician.

Statistical methods 

Harvard Clinical Research Institute (HCRI, Boston, Mass) performed data management and statistical analyses with SAS version 8.2 (SAS Institute Inc, Cary, NC). All analyses were based on the principle of intention-to-treat (ITT) and included eligible patients in whom an attempt was made to place the FilterWire EX/EZ across the target lesion.

The primary objective of the BEACH trial was to determine whether the 1-year major adverse event (MAE) rate in CAS patients at high surgical risk would be less than or equal to that of the weighted objective performance criterion (OPC), derived from historic controls of patients undergoing CEA.⁶, ⁷ The patient mix was adjusted as indicated below with ω_A and ω_C, representing the proportion of patients qualified by high-risk anatomic (A) and high-risk comorbid (C), respectively:

The 4% was the margin of equivalence and the remaining terms represented the 1-year event rate for the same population that would have been treated with CEA. For the purpose of this study and with consent from the Food and Drug Administration, π_OPC-Anatomic and π_OPC-Comorbid were set to 11% and 15%, respectively.

Continuous variables are presented as mean ± 1 standard deviation (SD). Categorical data are given as counts and percentages. Baseline characteristics were compared by bivariate analysis using two-sided Fisher exact test for categorical variables and two-sided Student t test for continuous variables. Bivariate comparisons involving more than two groups were done using the Kruskal-Wallis test. Cumulative freedom from primary endpoint was assessed by cumulative outcome estimates according to Kaplan-Meier¹⁵ and compared using log-rank test. Multivariable logistic regression analysis and Cox proportional hazards analysis was used to adjust for all baseline characteristics showing a difference in bivariate analysis with an entry level of P < .05. A P value <.05 was considered to indicate statistical significance.

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Results 

There were 189 patients in the roll-in cohort, 480 patients (167 women, mean age 70.9 ± 9.3) in the pivotal and 78 patients (23 women, mean age 71.1 ± 10 years) in the bilateral group.

Baseline and procedural characteristics 

The pivotal and bilateral groups differed slightly with regard to symptomatic status, history of other neurological events, history of previous CEA, current angina, target lesion localization, and de novo vs recurrent lesion (Table I and Table II). In the pivotal group, 41.2% qualified with comorbid risk factors and 58.8% had high risk anatomic features, resulting in a value of 16.6% for the weighted OPC. In the bilateral group, 32.1% qualified with comorbid risk factors and 67.9% had high risk anatomic features, resulting in a value of 16.3% for the weighted OPC. Technical success was 98.3% in the pivotal group and 97.4% for the first procedure in the bilateral cohort. Mean follow-up was 885 ± 320 days in the bilateral and 861 ± 343 days in the pivotal group. Of the 78 patients in the bilateral group, 57 returned to have the contralateral lesion treated.

Table I. Baseline patient characteristics

TIA, transient ischemic attack; CVA, cerebrovascular accident; CABG, coronary artery bypass grafting; CAD, coronary artery disease.

aContinuous data compared by Student t test, categorical data compared by Fisher test.

Table II. Target lesion characteristics

SD, Standard deviation; ICA/CCA, internal carotid artery/common carotid artery; DS, diameter stenosis.

aP value corresponds to the comparison between the pivotal group and first bilateral procedure.

bData available for 55 patients.

cData available for 27 patients.

Clinical outcomes 

The primary endpoint was 8.9% (40/447) with a one-sided 95% upper confidence limit of 11.5% for the pivotal cohort and 6.8% (5/73) with a one-sided 95% upper confidence limit of 13.9% for the first procedure of the bilateral cohort, both below their respective OPCs. There were no statistically significant differences between the bilateral and the pivotal groups with regard to any solitary component of the primary endpoint (Table III). At 5.8%, the primary endpoint for the second procedure in the bilateral cohort was similar to the first procedure (Table III). The rate of freedom from the primary endpoint was 93.6% for the first procedure in the bilateral cohort and 91.6% in the pivotal cohort at 1 year (P = .55 by log-rank, Fig). In a multivariable logistic regression model adjusted for symptomatic status, history of other neurological events, history of previous CEA, current angina, target lesion localization, and de novo vs recurrent lesion, no significant differences in primary endpoint was found comparing the pivotal and first bilateral procedure groups after 30 days (OR: 0.8673, 95% CI: 0.4590-1.6389, P = .66) and after one year (OR: 0.9102, 95% CI: 0.5503-1.5053, P = .73), respectively.

Table III. One-year rates of study endpoints comparing pivotal and bilateral group

MI, Myocardial infarction; NA, not applicable.

aIpsilateral and contralateral are relative to the target lesion of the first procedure.

bIpsilateral and contralateral are relative to the target lesion of the second procedure.

cP value corresponds to the comparison between outcomes for the pivotal group and first bilateral procedure.

dExcludes subarachnoid hemorrhage.

eRestenosis was defined as ≥70% diameter stenosis by duplex ultrasound.

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• Fig. 

  Kaplan-Meier analysis of primary endpoint. Cumulative freedom from major adverse events did not differ between patients from the pivotal and from the bilateral group (P = .5479 by log-rank).

The 30-day restenosis rate was 0% for the pivotal group and 1.3% for the first procedure in the bilateral group (P = .14). One-year restenosis rate was 9.3% in the pivotal and 12.5% in the bilateral group, respectively (P = .39). Target lesion revascularization rate was 0% and 4.7% in the pivotal group and 0% and 9.7% in the bilateral group after 30 days (P = NA) and after 1 year (P = .09), respectively.

Duplex ultrasound 

Results from follow-up duplex sonography are outlined in Table IV. No significant differences in preprocedural and follow-up duplex ultrasound findings were noted comparing pivotal and bilateral patients. In the bilateral group, the ICA/CCA peak systolic velocity (PSV) ratio prior to the procedure was 5.6 ± 3.4 and improved to 1.5 ± 0.7 immediately after the procedure (P < .0001) and remained improved through 1 year. There was no progression of ICA PSV_maximum over the latter 6 months of follow-up in either cohort.

Table IV. Follow-up duplex ultrasound findings

CI, Confidence interval; SD, standard deviation; ICA/CCA, internal carotid artery/common carotid artery; ICA-PSV_maximum, Internal carotid artery maximum peak systolic velocity.

aNumbers are mean ± SD.

bP value corresponds to the comparison between outcomes for the pivotal group and first bilateral procedure.

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Discussion 

Bilateral carotid disease is frequent⁶, ⁸, ⁹, ¹⁰ and was shown to substantially increase the risk for complications during and after unilateral CEA⁸, ¹⁶, ¹⁷ as well as after unilateral CAS.¹⁸ The present prospective series indicates that outcomes of high-risk patients undergoing staged bilateral CAS with a distal embolic protection filter compare favourably with those of patients undergoing unilateral CAS.

While the role of bilateral CEA simultaneously carried out in one surgical act is controversial,¹⁹, ²⁰, ²¹, ²² staged bilateral CEA with a few days in between procedures was shown to be a safe and effective treatment concept.²³, ²⁴ Rodriguez-Lopez and colleagues analyzed outcomes of 77 patients undergoing 154 bilateral CEAs within 4 days or less.²⁴ Sixty-five percent of these patients were symptomatic. The periprocedural transient ischemic attack (TIA) and stroke rate were 2.6% and 0.7%, respectively, thereby comparing favourably with a similarly composed group of patients undergoing unilateral CEA.²⁵ However, 30-day rates of nerve injury and non-neurological complications such as dysphagia and hoarseness due to trauma as well as haematomas were 10.6% and 11%, respectively.²⁴ Of note, absence of cranial nerve palsy is a major advantage of CAS documented with level-A evidence.⁵

The feasibility of bilateral CAS was first reported by Mathur and colleagues in 1997 ²⁶ and several case authors described encouraging patient outcomes after bilateral CAS for de novo stenoses,²⁷ post-CEA carotid restenoses,²⁸, ²⁹ fibromuscular dysplasia,³⁰ and Takayasu arteritis.³¹ Henry and colleagues retrospectively analyzed outcomes of 57 consecutive patients undergoing bilateral CAS.¹² In that series, 30% of patients underwent simultaneous CAS, whereas the remaining 70% were treated within a staged procedure. Furthermore, 68% of patients were symptomatic and embolic protection devices were used in 74% of patients. Incidence of stroke was 3.7%, and the rate of the composite endpoint consisting of stroke, death, and MI was 7.4% at 30 days.

To our knowledge, the present study represents the largest consecutive series of patients undergoing staged bilateral CAS in a prospective setting. We did not find statistically significant differences with regard to the 30-day and 12-month clinical outcomes comparing patients undergoing unilateral with those receiving staged bilateral CAS. The 30-day incidence of all strokes was 4.5% in the pivotal and 4.1% in the bilateral group, while the 30-day rate of ipsilateral stroke was 3.4% and 1.4%, respectively. Furthermore, the 30-day rate for death, stroke, and Q-wave MI was 5.4% in the pivotal and 4.1% in the bilateral group. Also, no significant differences were found when comparing ipsilateral stroke rates at 12 months. Thus, our results corroborate findings from Henry's retrospective series¹² and compare well with findings in earlier CAS trials in high-risk patients.⁵, ³² In Stenting and Angioplasty with Protection in Patients at High Risk for Endarterectomy (SAPPHIRE), the 12-month incidence of all strokes was 6.2 after CAS and 7.9 after CEA, whereas the rate of primary endpoint at 30 days (death, stroke, or MI plus ipsilateral stroke or death from neurological causes within 31 days to 1 year) was 12.2% after CAS.⁵ Furthermore, in the high-risk stent registry ACCULINK for Revascularization of Carotids in High-Risk patients (ARCHeR), the primary endpoint (a composite endpoint consisting of death, stroke, and MI at 30 days plus ipsilateral stroke at 1 year) was 9.6%.³² In the Stent-protected Percutaneous Angioplasty of the Carotid Endarterectomy (SPACE) trial, definition of the primary endpoint was slightly different compared with the ARCHeR and BEACH protocol, thereby rendering a direct comparison across these trials difficult.³³ However, the 30-day rate of all strokes was 7.7% after CAS and 6.5% after CEA in the SPACE study thereby being slightly higher compared with that in the present series. This observation, however, might be explained by the facts that the SPACE trial contained only symptomatic patients and that only 27% of patients were treated using an embolic protection device.

Early restenosis was reported to occur in 10 % to 24% of patients after carotid endarterectomy.³⁴, ³⁵ Comparison of restenosis rates after CAS and CEA between different trials has been hampered by varying definitions and the lack of reporting regarding symptomatic or asymptomatic status.³⁶ In various CAS trials, restenosis is usually defined based upon some degree of duplex measurement with secondary reporting of target vessel revascularization rates. The Carotid and Vertebral Artery Transluminal Angioplasty Study (CAVATAS) trial, in which restenosis rates of CAS and CEA were directly compared, used a cut-off ≥70% and reported a restenosis rate of 18.5% for CAS compared with 5.2% for CEA.³⁷ This trial used stents in only 22% of the endovascular patients, while the remaining 88% were treated with angioplasty alone. Thus, the comparatively high restenosis rate in that trial was almost certainly caused by the use of inferior techniques of balloon angioplasty during the early stages of development of carotid endovascular treatment in that trial.³⁷ The BEACH trial also used a cut-off of ≥70% and we found a 1-year restenosis rate of 9.3% in the pivotal and 12.5% in the bilateral group with differences not being statistically significant. In a recent systematic review on restenosis after CEA and CAS, the early restenosis rates after CAS compare well with those reported for CEA.³⁶ To date, only a few studies have analyzed the restenosis rates after CAS beyond 2 years. Thus, data from further trials is warranted to assess long-term patency rates of stented carotid arteries.

Shortcomings 

Although in the present series FDA-agreed OPCs for comparison with the current gold standard, CEA, were used, this study does not contain a direct randomized comparison with open surgery. Furthermore, the present study allowed CAS of the contralateral carotid lesion only 30 days after endovascular treatment of the primary target lesion. Thus, this study does not give insight into patient outcomes after simultaneous bilateral CAS. The concerns about simultaneous CAS seem to be the hemodynamic impairment from stimulation of the carotid sinus baroreflex and the risk of cerebral hyperperfusion syndrome.³⁸, ³⁹

Staged procedures have disadvantages including delay of definitive treatment of carotid lesions, higher costs, and inconvenience to the patient and could delay potentially lifesaving procedures.¹²

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Conclusions 

In the present series, both the pivotal and the bilateral group met the primary endpoint with a major adverse event rate below the FDA-agreed OPC. Thus, staged bilateral CAS is an efficient treatment option for patients at high surgical risk and bilateral carotid artery stenoses and does not yield inferior outcomes compared with unilateral stenting. Data from further prospective studies is warranted to confirm findings from the present study and to identify subgroups of patients that are at particular high risk for staged bilateral CAS.

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Author contributions 

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