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Head and Neck Imaging |
1 From the Departments of Angiology (S.S., M.S., W.M., T.N., R.A., E.M.) and Clinical Neurology (W.L.), University of Vienna Medical School, Austria. Received October 24, 2002; revision requested January 7, 2003; final revision received May 20; accepted June 18. Address correspondence to S.S., Department of Internal Medicine II, Division of Angiology, Vienna General Hospital, Medical Faculty, Währinger Gürtel 18–20/6J, A-1090 Vienna, Austria (e-mail: schila.sabeti@akh-wien.ac.at).
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ABSTRACT |
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 TOP ABSTRACT INTRODUCTIONMATERIALS AND METHODS RESULTS DISCUSSIONREFERENCES |
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MATERIALS AND METHODS: This study included 471 consecutive patients from a registry database who underwent elective ICA stent placement without cerebral protection for high-grade (greater than 70% stenosis of the ICA, according to the North American Symptomatic Carotid Endarterectomy Trial) symptomatic (n = 147) or asymptomatic (n = 324) ICA stenosis. Contralateral carotid arteries were investigated with angiography. Patients with and patients without contralateral high-grade stenosis (70%–99% stenosis, according to the North American Symptomatic Carotid Endarterectomy Trial) or occlusion were compared with respect to 30-day neurologic outcome by using the 
2 test and multivariate logistic regression analysis.
RESULTS: Neurologic events were observed in 33 patients (7%) with 15 transient ischemic attacks, eight minor strokes, and 10 major strokes that led to death in two patients (combined stroke and death rate, 4%). Eighty-eight patients (19%) with contralateral high-grade ICA stenosis and 43 patients (9%) with contralateral ICA occlusion exhibited a similar rate of postintervention combined neurologic events (n = 9, 7%) compared with patients without contralateral high-grade ICA stenosis or occlusion (n = 24, 7%) (P = .94). No differences were observed between symptomatic and asymptomatic patients. Combined stroke and death rates were also comparable between symptomatic (four of 131, 3%) and asymptomatic (14 of 340, 4%) patients (P = .59). Of all variables tested, multivariate analysis did not detect any predictor for peri- or postinterventional neurologic events.
CONCLUSION: Contralateral high-grade ICA stenosis or occlusion was not associated with an increased risk for neurologic events after elective ICA stent placement.
© RSNA, 2004
Index terms: Carotid arteries, interventional procedures, 172.1269 • Carotid arteries, stenosis or obstruction, 172.4311, 172.4312, 172.7213, 172.7214 • Stents and prostheses, 172.1269
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INTRODUCTION |
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TOPABSTRACTINTRODUCTIONMATERIALS AND METHODS RESULTS DISCUSSIONREFERENCES |
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The North American Symptomatic Carotid Endarterectomy Trial (NASCET) investigators reported an increased risk (14%) for perioperative stroke after carotid endarterectomy in patients with contralateral ICA occlusion (20,21). In contrast, previously published data obtained in a study that did not include control subjects but did include a small series of patients who underwent elective carotid stent placement suggested that contralateral ICA occlusion would not affect the safety of this procedure (22,23). We hypothesized that elective ICA stents could be placed safely in patients with contralateral high-grade ICA stenosis or occlusion. Thus, the aim of the present study was to compare the neurologic outcome after elective ICA stent placement in patients with and patients without contralateral ICA obstructions.
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MATERIALS AND METHODS |
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TOPABSTRACTINTRODUCTIONMATERIALS AND METHODS RESULTS DISCUSSIONREFERENCES |
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Inclusion and Exclusion Criteria
Candidates were initially identified on the basis of their clinical status and the presence of high-grade (>80%) ICA stenosis, as identified with duplex ultrasonography (US) and computed tomography (CT) of the head. Carotid stent placement indications were determined on the basis of an angiographically documented stenosis of 70% or more and according to criteria set forth by the NASCET investigators (18). In symptomatic patients, there had to be high clinical suspicion that the neurologic manifestations were due to microembolization from the carotid plaque, and the interval between the onset of hemispheric symptoms and the performance of the procedure had to be 6 months or less.
Patients who had a major stroke had to be treated within 6 weeks. Stent placement was indicated in asymptomatic patients if they had a high-grade (>80%) stenosis with rapid lesion progression within the past 6 months that was documented with duplex US, a high-grade (>80%) stenosis with silent cerebral infarction on CT scans that was consistent with thromboembolism from the carotid plaque, a very high-grade (>90%) stenosis, or a high-grade (>80%) stenosis with contralateral ICA occlusion (2). Stent placement was also indicated if a surgeon requested it before major (cardiac or neck) surgery (2). Patients were excluded if they were severely disabled as a result of a stroke or dementia, had a severe disease such as acute cardiac decompensation or acute metabolic dysfunction, were being treated for renal insufficiency without dialysis, or were being treated in the intensive care unit with mechanical ventilation. Other exclusion criteria were an intracranial tumor or a cerebral hemorrhage depicted with CT, peripheral arterial occlusive disease that prevented femoral artery access, and inability to give consent.
Patient Evaluation
Duplex US grading of the carotid stenosis was performed in accordance with the principles of the consensus meeting on the quantification of stenosis of the extracranial carotid artery (25) and the proposals of Nicolaides et al (26). US was performed 1 day before and 1 day after treatment by using a US scanner (XP 10; Acuson, Mountain View, Calif) with a 5-MHz linear probe or a scanner (System 5; Wingmed Sound, Horton, Norway) with a 10-MHz linear probe by two medical technical assistants and supervised by one of the authors (E.M.).
A complete neurologic history, including assessment with the National Institutes of Health Stroke Scale (27), was routinely performed by one independent neurologist (W.L.) before the intervention. Baseline cranial CT was mandatory in all patients. The clinical neurologic state of the patient prior to stent placement, in conjunction with a recent cranial CT study and a carotid duplex US study, formed the basis for the neurologist (W.L.) to give explicit consent for carotid stent placement. Routine neurologic examinations were performed by the same physician the day before, the day after, and 30 days after the intervention. If neurologic events were suspected, clinical evaluation with cranial CT and angiography was performed immediately.
Two authors in consensus (S.S., T.N.) used a standard questionnaire to record medical history and data from physical examinations. A standard laboratory examination included global coagulation tests, a complete blood cell count, measurement of glycosylated hemoglobin levels, and an assessment of the levels of total cholesterol, low-density lipoprotein cholesterol, high-density lipoprotein cholesterol, lipoprotein (a), and uric acid. Diabetes mellitus was defined as a fasting blood glucose level higher than 110 mg/dL (6.1 mmol/L) after being measured three times, abnormal results of oral glucose tolerance tests, and a glycosylated hemoglobin level of more than .065. Hyperlipidemia was defined as a fasting total cholesterol level higher than 200 mg/dL (5.17 mmol/L), a low-density lipoprotein cholesterol level higher than 130 mg/dL (3.37 mmol/L), or a triglyceride level higher than 180 mg/dL (2.03 mmol/L). All patients taking lipid-lowering medication were also considered to be hyperlipidemic. Arterial hypertension was diagnosed according to World Health Organization criteria. Peripheral artery disease was assessed in selected patients with clinical evaluation, ankle-brachial index measurements, duplex US, and angiography. Coronary artery disease was classified according to the Canadian Cardiovascular Society classification and was evaluated in selected patients with echocardiography, stress exercise testing, myocardium scintigraphy, or angiography.
Carotid Stent Placement
All stents were placed by one author (R.A.). Technical details of the stent placement procedure are described in another report (1). Briefly, a diagnostic four-vessel angiogram was obtained in all patients prior to the intervention to document anatomic variations, stenoses at the origin of the great vessels, severely diseased aortic arches, intracranial disease, and any vertebral and posterior circulatory problems. Procedures were begun with local anesthesia and transfemoral access. After placement of an 8-F sheath, every patient received 5,000 units of intraarterial heparin (Baxter, Vienna, Austria). An overview angiogram of the supraaortic arteries was obtained at the aortic arch, and a selective angiogram of the carotid artery and its intracranial branches was obtained in at least two planes. Length and grade of the lesion were documented, and a road map was established.
After the stenosis to the distal ICA was crossed with a gold-tip wire (Boston Scientific, Natick, Mass), a 3.5 x 40.0-mm balloon (Bijou; Schneider, Bülach, Switzerland) was placed at the site of the stenosis for primary dilation at 10 atm for 5–10 seconds. The catheter was exchanged, and 1 mg of atropine (Nycomed, Austria, Vienna) was administered intravenously immediately before deployment of a Wallstent (OTW; Boston Scientific), which was sized according to an estimation of the diameter of the carotid artery on the selective angiogram. Initially, a carotid Wallstent with rolling stent membrane (Schneider) was used. Later, an OTW Wallstent was applied. Stent deployment was followed by dilation within the stent by using a 5- or 6-mm-diameter balloon catheter and a pressure of 8–10 atm for 5 seconds.
After stent placement, selective control angiography in at least two planes was performed to evaluate the local result and to examine the intracranial arteries for changes in hemodynamics and embolization. An intervention was considered successful when the residual diameter reduction calculated from the final angiogram was less than 30%.
Standardized antiplatelet therapy was performed in all patients. The first 138 patients received 500 mg (two 250-mg doses) of ticlopidin (Sanofi-Synthelab, Vienna, Austria) per day, which was the only thrombocyte adenosine diphosphate inhibitor available at this time, and 100 mg of acetylsalicylic acid per day for 4 weeks. Acetylsalicylic acid was discontinued thereafter, and ticlopidin was continued for 1 year. After 138 patients received the medication, ticlopidin was replaced with an initial dose of 300 mg of clopidrogel (Plavix; Bristol-Myers Squibb, Paris, France) and followed by a dose of 75 mg/d, thereafter. Because of long-term side effects on blood cell formation, ticlopidin was replaced by clopidrogel as soon as it became available. Clopidrogel exerts the same action (adenosine diphosphate inhibition) on thrombocyte function as ticlopidin and has been described as equally effective, with fewer long-term side effects. Since both substances are equally powerful, this change in antithrombotic medication did not influence our results. After 1 year, patients were switched to a dose of 100 mg of acetylsalicylic acid per day.
Definitions of Neurologic Events
A neurologic event was categorized as a transient ischemic attack (TIA) or a minor or major stroke. A TIA was defined as a focal ischemic neurologic deficit with abrupt onset that resolved completely within 24 hours. A minor stroke was defined as a focal neurologic deficit that lasted more than 24 hours and had a National Institutes of Health Stroke Scale score lower than four. A major stroke was defined as a focal neurologic deficit that lasted more than 24 hours and had a National Institutes of Health Stroke Scale score greater than four. A combined neurologic event included a TIA and both types of stroke.
Statistical Analysis
Continuous data are given as the median and the interquartile range, which ranges from the 25th to the 75th percentile. Counts and percentages are given for discrete variables. The 2 test was used to compare proportions, and the Mann-Whitney U test was used for univariate comparison of continuous data. A multivariate binary logistic regression model was applied to assess an association of contralateral carotid artery stenosis and postinterventional neurologic events, while adjusting for possible confounding effects of other baseline variables. Baseline variables were selected for the final model either if they had a clinically or biologically plausible relation to the outcome or if they appeared to be imbalanced between patients with and patients without contralateral high-grade stenosis or occlusion, as indicated by P < .20 (28). Interaction was assessed by using multiplicative interaction terms, the linearity of the logit assumption was checked for continuous predictor variables, and an analysis of residuals was performed. Regression diagnostics and overall model-fit were performed according to standard procedures (29). The Homer-Lemeshow test was used for global goodness of fit testing. Results of the logistic regression model are given as the odds ratio and 95% CI. A two-sided P value of less than .05 was considered to indicate a statistically significant difference. An analysis of missing data was performed and compared demographic data, clinical characteristics, procedure-related variables, and neurologic events between patients with and patients without complete data by using 2 tests and Mann-Whitney U tests, as appropriate. Calculations were performed with statistical software (version 10.0; SPSS, Chicago, Ill). All statistical analyses were performed by one author (M.S.).
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RESULTS |
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TOPABSTRACTINTRODUCTIONMATERIALS AND METHODS RESULTS DISCUSSIONREFERENCES |
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Symptomatic ICA stenosis was treated in 147 (31%) of 471 patients. Of these 471 patients, 107 (23%) had a TIA up to 6 months prior to the intervention, three (1%) had a minor stroke, and 37 (8%) had an ipsilateral major stroke. Asymptomatic high-grade ICA stenosis was treated in 324 (69%) patients. One stent was deployed in 445 patients, two stents were deployed in 25 patients, and three overlapping stents were deployed in one patient. The procedure was successful in 448 (95%) patients and unsuccessful in 23 (5%) patients because of severe calcification, kinking of the artery, or elastic recoil.
Angiography demonstrated a contralateral high-grade ICA stenosis (70%–99% stenosis, according to NASCET criteria) in 88 patients (19%) and a contralateral ICA occlusion in 43 patients (9%). These contralateral lesions were all classified as asymptomatic. Thirty-eight patients (29%) with contralateral high-grade stenosis or occlusion were symptomatic in the treated side, and the remaining 93 patients (71%) were asymptomatic. Patients with contralateral ICA obstructions compared well with patients without contralateral ICA obstructions with respect to baseline characteristics, except for smoking and peripheral artery disease, which were found more frequently in patients with contralateral obstructions. Furthermore, a trend toward higher rates of arterial hypertension and prior myocardial infarction was observed in these patients (Table 1). Patients with contralateral ICA obstructions required more contrast material, because the contralateral ICA was documented more extensively.
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Cerebral embolization was detected in only four patients (1%) on the postintervention cranial angiogram. Early thrombotic reocclusion occurred in one patient who had a TIA. Other complications included pseudoaneurysms or hematomas at the site of arterial puncture in 19 patients (4%), transient periprocedure hypotension (systolic blood pressure below 90 mm Hg) in 32 patients (7%), and periprocedure transient bradycardia (heart rate below 50 beats per minute) in 11 patients (2%). Demographic data and clinical characteristics of patients with and without neurologic events (combined TIA, minor and major stroke, and death) are given in Table 2.
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Neurologic Events and Status of the Contralateral ICA
Eighty-eight patients (19%) with contralateral high-grade ICA stenosis and 43 patients (9%) with contralateral ICA occlusion exhibited a similar rate of postintervention neurologic events (nine of 131, 7%) compared with patients without contralateral high-grade ICA stenosis or occlusion (24 of 324, 7%) (P = .94). A post hoc power calculation with a level of significance of P = .05 revealed a power of 99% for demonstrating equivalence between these two groups. Combined stroke and death rates were also comparable between patients with (four of 131, 3%) and without (14 of 340, 4%) contralateral carotid obstruction (P = .59) (Table 3). Stratifying for symptomatic versus asymptomatic patients, contralateral high-grade ICA stenosis or occlusion was not associated with increased rates of neurologic events in both groups (Table 4).
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DISCUSSION |
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TOPABSTRACTINTRODUCTIONMATERIALS AND METHODS RESULTS DISCUSSIONREFERENCES |
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Currently, carotid stent placement is unlikely to offer any reduction in stroke risk compared with carotid endarterectomy (16), but stent placement may reduce neurologic events and nonstroke morbidity rates associated with surgical high-risk cases (19,30,31). Assuming equivalence between carotid endarterectomy and stent placement (16), there will certainly be indications for use of one technique or the other. Risk factors for complicated endarterectomy may not be relevant for carotid stent placement and vice versa. Identifying or excluding potential risk factors for neurologic events during or after elective carotid stent placement, therefore, is the basis to determine which patients are primary candidates for the endovascular procedure.
It has been suggested that ICA stent placement is safe and effective in patients with anatomy that puts them at risk for carotid endarterectomy (8,31–33). Previous ipsilateral endarterectomy, common carotid artery bifurcation above the mandibular angle, previous radiation therapy to the neck, or presence of severe comorbidities (ie, unstable angina) may be considered early indications for stent implantation. Whether patients with contralateral carotid occlusion may also benefit from endovascular treatment rather than surgery is debatable.
NASCET investigators reported an increased risk for stroke after endarterectomy in patients with contralateral carotid occlusions (21,34), which may be explained by a substantial alteration of cerebral blood flow in patients with contralateral ICA disease (35). In a systematic review including the 1,729 patients from the European Carotid Surgery Trial, Rothwell et al (36) also described a two-fold increased risk for perioperative stroke in patients with contralateral ICA occlusion. Others, however, either found no differences or found only a trend toward higher rates of neurologic events in patients with contralateral ICA occlusion (37,38), which may be due to smaller sample sizes and lack of statistical power. Nevertheless, contralateral carotid occlusion is currently considered a risk factor during endarterectomy, and our data indicate that elective carotid stent placement may be a feasible alternative for these patients.
In the present study, predictors of neurologic events during or after carotid stent placement could not be detected by evaluating a large number of potential clinical risk factors. Previous reports suggested that increasing age had a negative effect on the rate of complications in patients who underwent carotid stent placement (9,19,39); however, results of a prior study (24) and our results indicate that increasing age was not significantly associated with periprocedure stroke. Unlike surgery (36), cardiovascular comorbidities did not seem to influence 30-day neurologic outcome. This confirms data in previous publications about the safety of carotid stent placement in high-risk patients (8,14,32). Patients with pending ICA revascularization who exhibit advanced atherosclerotic comorbidities, therefore, may be considered good candidates for stent placement rather than endarterectomy (14), although the results from the ongoing randomized controlled trials (18) remain to be seen before final recommendations can be made.
Data were derived from a single-center registry database and, therefore, may be prone to selection bias. Since this was a prospective registry from a single center, however, and a single operator gathered data, we are sure that no patients were missed in this registry.
Although the number of patients in the present series is one of the largest in the literature, the fact that we found no difference between patients with and patients without contralateral ICA obstruction does not mean that these differences can be excluded with certainty. Demonstrating equivalence with a power of 99%, however, suggests that even if these differences exist they may be clinically irrelevant.
Another limitation is the absence of cerebral protection devices in this series; therefore, our conclusions refer only to unprotected ICA stent placement. Nevertheless, from the data available so far, it seems reasonable to speculate that the use of protection devices improves the safety of ICA stent placement, making the status of the contralateral ICA probably even more irrelevant for the neurologic event rate. Starting in January 2002, all patients at our institution underwent protected ICA stent placement, if technically possible.
In conclusion, contralateral high-grade ICA stenosis or occlusion was not associated with an increased risk of neurologic events after elective carotid stent placement; therefore, unprotected carotid stent placement could be performed safely in these patients.
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FOOTNOTES |
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Author contributions: Guarantors of integrity of entire study, S.S., M.S., E.M., R.A.; study concepts, S.S., M.S., W.M., E.M.; study design, S.S., M.S., E.M., R.A.; literature research, S.S., T.N., M.S.; clinical studies, S.S., M.S., W.M., W.L., R.A., E.M.; data acquisition, T.N., S.S., W.M.; data analysis/interpretation, all authors; statistical analysis, M.S., W.M.; manuscript preparation, S.S., M.S., W.M., R.A.; manuscript definition of intellectual content, all authors; manuscript editing, S.S., M.S.; manuscript revision/review, S.S., M.S., W.M., E.M.; manuscript final version approval, all authors
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REFERENCES |
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TOPABSTRACTINTRODUCTIONMATERIALS AND METHODS RESULTS DISCUSSIONREFERENCES |
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