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Vascular and Interventional Radiology |
1 From the Interventional Neuroradiology Unit, Departments of Diagnostic and Interventional Radiology (E.C.K., M.S.K., G.P.v.S., W.M.), Vascular Surgery (M.M.L.B.), and Neurology (E.G.S.W.), Royal Perth Hospital, Perth, Australia. Received July 20, 2000; revision requested September 13; final revision received February 5, 2001; accepted March 9. Address correspondence to E.C.K., Department of Radiology, University Hospital, Petersgraben 4, 4031 Basel, Switzerland (e-mail: ekirsch@uhbs.ch).
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ABSTRACT |
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 TOP ABSTRACT INTRODUCTIONMATERIALS AND METHODS RESULTS DISCUSSIONREFERENCES |
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MATERIALS AND METHODS: Carotid arterial stent placement was attempted in 57 arteries in 53 patients. Thirty-six (68%) of 53 patients were symptomatic. Forty-two (79%) of 53 patients had one to three clinically important comorbidities and were considered at high risk. All patients underwent pre- and postprocedural independent neurologic examinations. Follow-up consisted of serial duplex ultrasonography and clinical assessment.
RESULTS: The immediate technical success rate of stent deployment was 97%. Periprocedurally, three (three [5%] of 57 interventions) transient ischemic attacks and three (three [5%] of 57 interventions) minor strokes occurred. Two deaths occurred in the first 30 days (one myocardial infarction, one renal failure). One ipsilateral major stroke occurred 3 weeks after the procedure. The 30-day ipsilateral major stroke and death rate was 5% (three of 57 interventions). At 30 days, one of three patients with minor stroke had mild residual dysphasia. Treatment remained clinically successful in 48 (96%) of 50 patients. The restenosis rate was 4% (two patients).
CONCLUSION: Carotid arterial stent placement in a high-risk population has morbidity and mortality rates comparable to those of carotid endarterectomy in a lower risk population. Carotid arterial stent placement can be performed with a low restenosis rate.
Index terms: Carotid arteries, interventional procedures, 172.1269 • Carotid arteries, stenosis or obstruction, 172.721 • Carotid arteries, transluminal angioplasty, 172.1269
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INTRODUCTION |
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TOPABSTRACTINTRODUCTIONMATERIALS AND METHODS RESULTS DISCUSSIONREFERENCES |
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The purpose of this study was to describe our results, complications, and follow-up data after stent placement for occlusive ICA disease in a series of 53 patients and to compare the results with those in the literature.
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MATERIALS AND METHODS |
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TOPABSTRACTINTRODUCTIONMATERIALS AND METHODS RESULTS DISCUSSIONREFERENCES |
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The major risk factors for vessel atherosclerosis and the clinical comorbidities of the patients are listed in Table 1. Fifteen (28%) of 53 patients had one, 21 (40%) had two, and 14 (26%) had three or four major risk factors for atherosclerosis at presentation. In addition, 13 patients had one, 19 patients had two, and 10 patients had three clinically important comorbidities, including symptomatic coronary arterial disease, peripheral vascular occlusive disease, symptomatic valvular heart disease, age older than 79 years, obesity, or pulmonary insufficiency. Eleven patients had no comorbidities at presentation. Thirty-nine (74%) of patients treated would have been excluded from the North American Symptomatic Carotid Endarterectomy Trial (NASCET) (9) for the reasons given later in this article. Thirty-six (68%) of the patients were symptomatic, and 17 (32%) were asymptomatic (Table 2).
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Forty-eight (83%) of 57 lesions were of atheromatous origin. Nine lesions were restenoses; eight occurred after carotid endarterectomy and one after stent placement. The degree of stenosis was preprocedurally defined according to the NASCET angiographic protocol (9), with each stenosis documented in three planes. All treated stenoses measured at least 70% (range, 70%–99%). The mean stenosis was 92% in the asymptomatic group, and it was 87% in the symptomatic group. In the asymptomatic group, eight patients had restenosis after previous carotid endarterectomy, six were to undergo major surgery including cardiac bypass graft placement, and three had rapidly progressive stenosis with contralateral occlusion or high-grade stenosis. Significant contralateral carotid arterial stenosis or occlusion was present in 24 (45%) patients (70%–90%, n = 9; greater than 90%, n = 5; occlusion, n = 10). Cranial CT or MR imaging was performed in all patients to document or exclude recent infarction or mass lesion.
Indications and Patient Selection
Indications for carotid arterial stent placement were (a) symptomatic lesions causing at least 70% stenosis; (b) asymptomatic progressive stenosis greater than 80%; or (c) recurrent post–carotid endarterectomy stenosis greater than 70%.
Exclusion criteria included patient unwillingness or inability to give informed consent, recent lobar cerebral infarct or intracranial hemorrhage, known malignant tumor, severe renal failure, and allergy to contrast media. Patients with aortoiliac bypass grafts were usually excluded because of additional potential morbidities of graft puncture with a large sheath (ie, bleeding, infection). Despite this, four patients with grafts were treated because they were at high risk of undergoing surgery. Suspicion of carotid arterial plaque thrombus or subjective appreciation of deep ulceration at the time of angiography was considered a relative contraindication. Four potential candidates were not considered for treatment because of these findings at separate diagnostic examinations. However, no patients were excluded when angiography was performed as part of stent placement based on adverse angiographic findings.
Most patients were considered for endovascular therapy because they were at high risk of undergoing surgery because of severe ischemic heart disease, valvular heart disease, poorly controlled hypertension, advanced age, decompensated diabetes, or hepatic disease. A high carotid arterial bifurcation and the patients’ preference also were considered. The following exclusion criteria from the NASCET trial were not considered contraindications: age older than 79 years; organ failure of the liver, heart, or lung; nonatherosclerotic stenosis; cardiac valvular lesion or rhythm disorder of a type likely to be associated with cardioembolic cerebral symptoms; previous ipsilateral carotid endarterectomy; uncontrolled diabetes or hypertension; unstable angina or myocardial infarction within the previous 6 months; contralateral carotid endarterectomy within the previous 4 months; or major surgical procedure within the previous 30 days (9).
Technique
Patients received orally administered aspirin (Aspirin Cardio; Bayer, Leverkusen, Germany), 100 mg, once a day and ticlopidine (Ticlid; Sanofi-Winthrop, Surrey, England), 250 mg, three times a day for at least 3 days before the procedure. All procedures were performed with the assistance of a neuroanesthesiologist who administered intravenous sedatives.
In all cases, femoral arterial access was obtained prior to 5-F catheter placement in the common carotid artery (CCA). Diagnostic cervical and three-vessel cranial angiography was then performed. The target vessel was studied in three planes to measure the diameter of the CCA and ICA by using the integrated calibration system in the angiography unit (Neurostar; Siemens, Erlangen, Germany) to determine the balloon and stent size required. The degree of stenosis was determined by using the NASCET criteria (9). An exchange was performed with a 0.035-inch heavy-duty guide wire (Amplatz; Cook, Brisbane, Australia) to either a 7-F 100-cm-long sheath (Super Arrow-Flex; Arrow International, Reading, Pa) or a 9-F guiding catheter (Vista Brite Tip; Cordis Endovascular, Miami, Fla). The 7-F sheath system was used in patients with vessels in which catheter placement was easy, whereas the 9-F guiding catheter was used in patients with tortuous supraaortic vessels. An arch aortogram was not obtained.
The long sheath or guiding catheter was placed in the CCA and flushed continuously with pressurized heparinized isotonic saline (5,000 IU of heparin per liter). Heparin was administered intraarterially as a 5,000-unit bolus after sheath insertion. The activated clotting time was maintained two to three times prolonged compared with the baseline (250–350 seconds), with additional aliquots of heparin administered as required.
Glycopyrrolate (Robinal; Wyeth, Philadelphia, Pa), 0.4 mg, was administered intravenously prior to traversing the stenosis with a 0.016-inch micro guide wire (Taper; Target Therapeutics, Fremont, Calif) with road-map guidance. Glycopyrrolate acts longer than does atropine and lasts the length of the procedure. Predilatation was performed with a 4-mm-diameter balloon catheter (Savvy; Cordis Endovascular) until the balloon waist was obliterated. After this, the wire was exchanged for a 0.018-inch exchange wire (Roadrunner; Cook), and the stent was placed across the carotid arterial stenosis. The 6-F stent was sized to the diameter of the CCA. To ensure adequate apposition of the stent to the arterial wall, it is recommended to oversize the stent by 2 mm. This resulted in use of nominal 10-mm-diameter stents in most men and 8-mm-diameter stents in most women. Stent lengths were 20 or 30 mm.
After stent deployment, angioplasty was performed at the point of residual ICA stenosis by using a 5- or 6-mm-diameter balloon catheter, depending on the measured diameter of the ICA. The balloon length was 2 or 4 cm. The aim was to inflate the balloon only once with an inflation device (Encore; Meditech, Westwood, Mass) to a pressure of 6 atm until the waist of the stent was obliterated. Inflation times were kept as short as possible, less than 10 seconds, both for predilatation and during stent dilatation. The balloon catheter was withdrawn into the guiding catheter, leaving the guide wire across the treated lesion, and postangioplasty angiograms were obtained (Fig 1). A residual stent waist of less than 20% after angioplasty was deemed satisfactory and not redilated. Ipsilateral intracranial angiography was performed at the end of the procedure to exclude embolic vessel occlusion and to look for segmental slowing of contrast material transit, which can be associated with emboli sludging. The average procedure took 60–90 minutes. The average volume of contrast material used was 100 mL.
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Follow-up, Data Collection, and Definitions
The patients were followed up with duplex US and clinical neurologic examinations 1 day and 3, 6, and 12 months after the procedure. Subsequently, the patients were followed up once a year. Angiography was performed only when restenosis was suspected at US.
All patients’ clinical and angiographic data were analyzed and recorded on standard forms (by E.C.K., W.M., M.S.K.). Reversible neurologic deficits, minor or major stroke, and death were recorded during the preprocedural period, at 2 weeks, during the first 30 days, and at 6 months. Neurologic complications were classified as transient ischemic attacks with a focal ischemic neurologic deficit of abrupt onset resolving completely within 24 hours. A minor stroke was defined as a nondisabling deficit persisting longer than 24 hours; a major stroke was defined as disabling, with a persistent neurologic deficit (10).
Comorbidities were considered clinically important risk factors, as identified by Sundt et al (11), that increase the mortality and morbidity from carotid endarterectomy. An intervention was considered technically successful if a stent was well deployed and the degree of residual stenosis was less than 20% at the end of the intervention. The definition of a treatment remaining clinically successful in the follow-up period was the absence of any new neurologic symptom referable to the treated side and a lack of recurrent stenosis on the basis of the percentage of stenosis identified at duplex US.
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RESULTS |
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TOPABSTRACTINTRODUCTIONMATERIALS AND METHODS RESULTS DISCUSSIONREFERENCES |
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Sixty-one stents were deployed, with two stents deployed in six patients to cover the full length of the lesion. The preoperative noninvasive assessment of stenosis was confirmed in degree (>70% in symptomatic patients or in those with restenosis; >80% in asymptomatic patients) by using the procedural angiographic assessment in all cases. The measured stenosis at angiography did not alter the patients’ status with respect to need to treat in any case. There were no cases of severe preprocedural spasm or flow-limiting dissection. The 9-F guiding catheter was used in 37 interventions; the 7-F sheath, in 20 interventions. Seven patients experienced transient bradycardia at the time of balloon catheter inflation in the carotid arterial sinus or later in the intensive care unit and required medical treatment with glycopyrrolate. No patient required a temporary pacemaker. In some patients, transient cervical pain occurred during stent dilatation. In eight patients, we observed a lack of apposition of the distal stent to the ICA walls. We elected not to treat with redilatation or further stent implantation. In all eight patients, we observed the well-opposed ends of the stents on follow-up carotid arterial duplex US examinations.
Complications
Table 3 provides a summary of all neurologic events. Six neurologic complications occurred periprocedurally: three transient ischemic attacks and three minor strokes. Two minor strokes followed repeat dilatation of the stent after initial stent angioplasty demonstrated a residual stenosis of greater than 30%. One minor stroke occurred after angioplasty of a stenosis, which was preceded by a small non–flow-limiting dissection of the plaque during microwire cannulation. CT in patients with periprocedural neurologic events revealed small cortical infarcts in the three patients with minor strokes. There were no cases of intracerebral hemorrhage. In one patient (patient 32), repeat angiography was performed for mild progressive dysphasia occurring 2 hours after the initial procedure, with normal results.
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There were two procedure-associated deaths within the first 30 days. The first, an 81-year-old male high-risk patient (patient 13), had chest pain 3 hours after carotid arterial stent placement and had developed a subendocardial infarction at electrocardiography. He was examined by the cardiology service, thought unsuitable for further intervention, and treated medically. He made a slow recovery but died unexpectedly 2
weeks later following a further myocardial infarction. The second, a 71-year-old male high-risk patient (patient 20), developed deterioration of renal function during the postinterventional period and died 28 days later of acute renal failure, which was probably caused by the contrast media. A total of 110 mL of contrast media had been administered, and the patient had had an initial serum creatinine level of 180 µmol/L. Dialysis was declined because of multiple comorbidities such as ischemic heart disease with previous myocardial infarction, stroke with residual left-sided hemiparesis, and severe peripheral vascular occlusive disease. The ipsilateral major stroke and death rate at 30 days was 5% (three of 57 interventions).
Three of the strokes and both deaths occurred in the first 25 treated patients, with only one minor stroke in the subsequent 28 patients. Six of the seven neurologic complications occurred in symptomatic patients. There was no significant difference in perioperative morbidity when comparing symptomatic patients with and symptomatic patients without high rates of comorbidity. All 17 asymptomatic patients were initially treated without any resultant neurologic complications. Half of these were considered to be at high risk. One neurologic complication occurred in one asymptomatic patient treated for stent restenosis (Table 3).
In three (5%) of 57 interventions, arterial access site problems in the groin (one patient had an implanted aortobifemoral graft) were associated with aortoiliac disease requiring surgical repair; two of the repairs were performed with the patient receiving local anesthesia.
Follow-up
No patients were lost to follow-up. At least 12 months of follow-up was available in 48 patients or 52 treated arteries (died, n = 3; stent not placed, n = 2). At 5 months, one patient died of aggressive gastric carcinoma diagnosed after stent placement.
There were no further neurologic events at the 6-month outcome period and no sequelae of any strokes. The patient with mild residual dysphasia at 30 days had functionally recovered. This led to a 4% (n = 2) 6-month clinical outcome rate for all minor and major strokes and deaths related to vascular disease.
The mean follow-up period was 23 months (range, 12–42 months). Forty-six patients remained clinical successes. No restenosis was detected after 6-month follow-up. In two (4%) patients, there was asymptomatic early restenosis within 6 months. The first (patient 31) was a 92-year-old bedbound woman who presented with a 90% ipsilateral stenosis, contralateral ICA occlusion, and critical aortic stenosis. Her persistent postural cerebral hypoperfusion disappeared after uncomplicated carotid arterial stent placement. Six-month follow-up duplex US demonstrated 70% restenosis. Repeat treatment was declined because she was asymptomatic. In the second (patient 32), high velocities at duplex US suggested 90% restenosis. This was confirmed with angiography and treated with repeat stent placement after balloon dilatation was unsuccessful (Fig 2). Normal velocities were restored. She developed 40% restenosis at 3 months after repeat stent placement; it had not progressed at 1-year follow-up.
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DISCUSSION |
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TOPABSTRACTINTRODUCTIONMATERIALS AND METHODS RESULTS DISCUSSIONREFERENCES |
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There is a wide range of published complication rates in carotid endarterectomy. Rothwell et al (15) published a systematic review of the risks of stroke and/or death due to endarterectomy for symptomatic carotid arterial stenosis in 51 studies published between 1980 and 1996. The overall mortality rate was 1.6%, and the risk of stroke and/or death was 5.6%. However, the risk varied systematically with the study methods and authorship. Winslow et al (16) reported a major complication rate (major stroke and death within 30 days after surgery) for carotid arterial endarterectomy of 9.8% in a random sample of 1,302 patients in three geographic areas across the United States.
The reported stroke and death rates following carotid arterial stent placement are largely similar to or even better than those for the published data on carotid endarterectomy, although the patient populations and their assessments may not be strictly comparable. At 30 days, a major stroke and death rate of 2.4%–2.7% has been reported in nonselected groups of patients (17–19). The rate of complications is reported to decrease with experience with this new technique. On an annual basis, the incidence of minor stroke declined from 6.8% (1994–1995) to 4.0% (1997–1998), with no major strokes or neurologic deaths occurring during the 1997–1998 period, as reported by Vitek et al (20).
In high-risk patients, the published rates of major stroke and death are higher: 4.0%–7.7% (21–23). This is comparable with the 5.3% rate in our series. According to the risk factors of carotid endarterectomy originally defined by Sundt et al (11), 79% of our patients had clinical comorbidities that placed them in the high-risk category. One (2%) of our patients died of myocardial infarction 2 weeks after the procedure. Authors of the NASCET study reported cardiac complications of carotid endarterectomy of 3.9% even in a highly select patient group, from which patients with unstable angina or myocardial infarction within the previous 6 months had been excluded (12). Overall, 39 (74%) of 53 treated patients in the current study would have been excluded from the NASCET trial.
Although surgeons at our institution perform carotid endarterectomy with the patient under local anesthesia, the use of general anesthesia is widespread. The risk of myocardial infarction during anesthesia is increased for patients with ischemic heart disease or severe hypertension (11). Patients with unstable coronary disease that manifested as angina pectoris were found to have a 15% risk of myocardial infarction and as much as an 18% risk of death with carotid endarterectomy (24). Other anesthetic risks accompanying carotid endarterectomy include pneumonia, deep venous thrombosis, and pulmonary embolism (25). Patients with increased risk at carotid endarterectomy, especially when performed with the patient under general anesthesia, could be considered for carotid arterial stent placement, which is performed with the patient under intravenous sedation.
The most obvious risk of carotid arterial stent placement is embolic stroke during angioplasty. In our experience, embolic events occurred at the time of balloon inflation after stent placement. A scissoring action of the stent against damaged plaque may cause and repeated angioplasty may exacerbate such an event (20). Cerebral protection devices, which are in development at this time, may help to reduce the number of embolic complications. Theron et al (26) reported the results of 136 procedures performed with cerebral protection. There were no embolic complications among the 43 patients who underwent angioplasty only, whereas there were two (2%) embolic complications among the 93 patients who underwent stent placement. However, Henry et al (27) reported two major complications in 32 patients despite using the cerebral protection device of Theron et al (26).
Severe bilateral disease may play an additional role in periinterventional neurologic complications. In the group with neurologic complications studied by Diethrich et al (19), four of the 12 patients had significant contralateral ICA stenosis greater than 75%. Despite this, in our series, stent placement was well tolerated in 24 (45%) patients with significant contralateral stenoses or occlusions. Similarly, Mericle et al (28) reported no neurologic complications in 23 high-risk patients with contralateral occlusions.
Apart from cerebrovascular complications, there are other risks associated with carotid endarterectomy. Authors of the NASCET study reported cranial nerve palsy (7.6%), wound hematoma (5.5%), and wound infection (3.4%) (12). Cranial nerve palsy is reported to occur in 12%–27% of patients who undergo carotid endarterectomy (29). In the current series, none of the preceding complications occurred. In carotid arterial stent placement, a 5.4% rate of problems with the femoral arterial access site has been reported (19), similar to the 5% in the current study.
Carotid arterial stent placement has some advantages, as compared with carotid endarterectomy. The stent placement procedure avoids an incision in the neck and is performed with the patient under local anesthesia with conscious sedation. A stent can be placed in surgically inaccessible lesions (high ICA stenosis) and for stenoses after endarterectomy or radiation therapy. The technical success rate of carotid arterial stent placement is high. Authors of published studies of series of patients undergoing carotid arterial stent placement (17–19,30) have reported procedural technical success rates of 93.2%–99.0%, comparable with the 97% rate in the current series.
ICA stent placement carries the risk of vagal stimulation in the carotid sinus at the time of balloon inflation, resulting in bradycardia or even asystole. These clinical signs normally respond promptly to balloon deflation, asking the patient to cough, or intravenous injection of glycopyrrolate. The seven (13%) patients in our study with bradycardia are in contrast with data from other authors (18,22), who reported significant bradycardia in 67% and 71% of patients, respectively. Of the 33 patients in the series of Smedema and Saaiman (31), three developed asystole for a maximum of 10 seconds, and four experienced bradycardia for a maximum of 20 seconds.
The recurrent stenosis rate after carotid endarterectomy is 3.5%–4.0% (32), although restenosis rates as high as 15% have been reported (33). Carotid arterial stent placement may have a special indication with this clinical entity, because scarring from the initial operation makes repeat carotid endarterectomy difficult, probably with a higher complication rate (32). Eight (15%) of the cases in the current study were recurrent asymptomatic stenoses following carotid endarterectomy. All patients were treated without complications. In small published series of patients with carotid arterial restenosis after carotid endarterectomy (34,35), stent placement appeared to be a safe and well-tolerated procedure with complication rates less than 4% and good patency rates at follow-up.
Treatment of asymptomatic stenosis is still controversial and needs further refinement. Authors of a recent report (36) noted that 45% of events in patients with high-grade asymptomatic stenosis were ascribable to lacunar or cardioembolic events. We merely selected patients who were being considered for surgery but acknowledge that the role of nonmedical therapy for asymptomatic stenosis is still not fully accepted.
In the current series, the stents remained fully patent in 96%, with two (4%) asymptomatic restenoses. Similar restenosis rates of 4.0%–4.9% after stent placement have been published in single studies (18,26). In multicenter surveys (17,37), restenosis rates of 1.99%–3.46% at 6 and 12 months have been reported.
In conclusion, carotid arterial stent placement appears to be a safe and reliable procedure for the treatment of ICA stenosis, even in high-risk patients. The indication from our mid-term follow-up data is that there is a low restenosis rate, and the long-term outcome may be satisfactory. Prospective direct comparative trials with similar patient populations will be necessary for a fair evaluation of carotid endarterectomy and stent placement.
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ACKNOWLEDGMENTS |
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FOOTNOTES |
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Author contributions: Guarantor of integrity of entire study, E.C.K.; study concepts and design, E.C.K., W.M., M.S.K., G.P.v.S.; literature research, E.C.K., W.M., M.S.K.; clinical studies, all authors; data acquisition, E.C.K., W.M.; data analysis/interpretation, E.C.K., W.M., M.S.K.; manuscript preparation, E.C.K.; manuscript definition of intellectual content and editing, all authors; manuscript revision/review, E.C.K., W.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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