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Thirty-day outcome of carotid artery stenting in Chinese patients: a single-center experience

JIAO, Li-qun; SONG, Gang; LI, Shen-mao; MIAO, Zhong-rong; ZHU, Feng-shui; JI, Xun-ming; YIN, Guo-yang; CHEN, Yan-fei; WANG, Ya-bing; MA, Yan; LING, Feng

doi: 10.3760/cma.j.issn.0366-6999.20131870
Original article
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Background Carotid artery stenting (CAS) as a competing treatment modality has had to adhere to limits to gain widespread acceptance in some studies. This study analyzed the clinical data of 1700 consecutive patients after CAS to retrospectively evaluate the 30-day outcome of CAS for internal carotid artery stenosis in a Chinese population.

Methods Medical records of 1700 patients who underwent CAS at Xuanwu Hospital affiliated to Capital Medical University between January 2001 and August 2012 were reviewed. Postoperative 30-day complication rates were analyzed and compared with those of other studies. Univariate and multivariate Logistic regression analyses were used to identify factors associated with perioperation myocardial infarction (MI), stroke, and death.

Results The overall 30-day rate of MI, stroke, and death after CAS was 2.53%. In univariate analysis, patients who were symptomatic, had a neurological deficit (modified Rankin score (mRS) ≥3; P=0.001), and who were not taking statins experienced a significantly increased rate of MI, stroke, and death (P=0.017). In multivariate Logistic regression analysis, the presence of symptoms (odds ratio (OR)=2.485; 95% confidence interval (CI)=1.267-4.876; P=0.008) and a neurological deficit (mRS ≥3) (OR=3.025; 95% CI=1.353-6.763; P=0.007) were independent risk factors for perioperative MI, stroke, and death.

Conclusions According to this single-center experience, CAS may effectively prevent and treat carotid artery stenosis that would otherwise lead to stroke. Being symptomatic and having a neurological deficit (mRS ≥3) increased the risk of perioperative MI, stroke, and death.

Department of Neurosurgery, Xuanwu Hospital, Capital Medical University, Beijing 100053, China (Jiao LQ, Song G, Li SM, Miao ZR, Zhu FS, Ji XM, Yin GY, Chen YF, Wang YB, Ma Y and Ling F)

Correspondence to: Dr. LING Feng, Department of Neurosurgery, Xuanwu Hospital, Capital Medical University, Beijing 100053, China (Tel & Fax: 86-10-83198836. Email: jiaoliqun@gmail.com) This work was supported by a grant of National 12th 5-year Supporting Project (No. 2011BAI08B00).

(Received July 16, 2013)

Edited by JI Yuan-yuan

The North American Symptomatic Carotid Endarterectomy Trial (NASCET), the European Carotid Surgery Trial (ECST), and the Asymptomatic Carotid Atherosclerosis Study (ACAS) demonstrated the efficacy and safety of carotid endarterectomy (CEA) in preventing cerebral stroke.1–3 The American Heart Association guidelines for CEA reflect these studies and recommend an upper limit of perioperative stroke and death risk of 6% for symptomatic patients and 3% for asymptomatic patients.4 Carotid artery stenting (CAS) as a competing treatment modality has had to adhere to these limits to gain widespread acceptance in some studies.5–10

In this study, we analyzed the clinical characteristics and outcomes of 1700 consecutive patients after CAS for internal carotid artery stenosis in a Chinese population and retrospectively evaluated our experience.

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METHODS

Database

Detailed clinical information was obtained from the Neurosurgery Department of Xuanwu Hospital affliated to Capital Medical University for patients who underwent CAS between January 2001 and August 2012. This retrospective study was conducted at a single center with 1700 consecutive CAS cases. The variables analyzed included patients' demographic characteristics (e.g., age and sex), comorbidities, neurological status before CAS, the degree of carotid stenosis, anesthesia, intraoperative parameters (e.g., types of stents used, embolic protection devices (EPDs), and balloon predilatation), and postoperative complications within 30 days of surgery (e.g., myocardial infarction (MI), stroke, and death). Patients who received bilateral carotid artery stents were counted once. The implanted stents included WallStent, Precise, Acculink, or Protéro stents. Patients were considered symptomatic if they experienced contralateral limb symptoms or eye amaurosis; symptoms of dizziness were excluded.

Before CAS, no new infarction within 3 weeks was found in any patient by computed tomography (CT) or magnetic resonance imaging (MRI). CAS was performed in all cases on the basis of identification of carotid artery stenosis on duplex ultrasound and digital subtraction angiography (DSA), the NASCET standard.11 Aspirin (100 mg) and clopidogrel (75 mg) or ticlopidine (250 mg) was administered routinely for 3 days preoperatively. Aspirin (100 mg) and clopidogrel (75 mg) or ticlopidine (250 mg) was administered postoperatively for 3 months at least. Then, aspirin (100 mg) or clopidogrel (75 mg) was administered for the patients' lifetime after postoperative 3 months. The procedures were performed with patients under general or local anesthesia by five interventionalists. Selected EPDs (e.g., Angioguard Cordis, RX-ACCUNET Abbott, SpiderRX Ev3, or FilterWireEZ Boston) were used based on whether those were difficult to use or not. The use of a balloon (e.g., Aviator, PowerFlex P3, Cordis Endovascular, RX-Viatrac, Abbott, or Invatec) for predilatation or postdilatation depended on the degree of stenosis. The carotid stents used included those from Wallstent, Boston Scientific, Precise Cordis, Acculink Abbott, or Protéro Ev3. Primary end points included perioperative MI, stroke, and death. Stroke was defined as persistence of a clinical neurological deficit for more than 24 hours, which is the same criterion used in the NASCET.11 Diagnosis of MI required two of the following conditions: chest pain, myocardial enzyme, or electrocardiogram (ECG) abnormalities. CT or MRI of the head was performed if cerebrovascular events were suspected.

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Statistical analysis

Statistical analyses were performed using SPSS version 18.0 (IBM Corporation, Somers, NY, USA). Mean ± standard deviation (SD) values were calculated for continuous variables. Pearson's χ2-test or Fisher's exact test was used for comparisons between categorical variables. Univariate tests were compared with Pearson's χ2-test or Fisher's exact test. All tests were two-tailed, and the level of significance was set at P <0.05. Multivariate Logistic regression was carried out to assess risk factors for postoperative MI, stroke, and death for all patients. Preoperative variables were entered into the multivariate regression analysis, and then stepwise selection was used in the regression analysis to determine which variables remained in the final model. Odds ratios (ORs) and 95% confidence intervals (CIs) were calculated for 30-day postoperative MI, stroke, and death rate.

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RESULTS

Patient characteristics

A total of 1700 patients with 1710 diseased carotid arteries underwent CAS procedures and were included in this study. Ten patients with diseased bilateral carotid arteries underwent bilateral CAS procedures at the same time and were thus counted as one procedure. The procedure success rate was 100%. Overall, the study patients had an average age of (64.95±8.65) years (range 35-88 years), and 85.65% of patients were men. Detailed patients' characteristics were showed in Table 1.

Table 1

Table 1

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Preoperative imaging

DSA identified 1593 patients who had a 70%-99% ipsilateral stenosis and 26 who had a >99% occlusion. Eighty-one patients had contralateral carotid severe stenosis.

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Stent placement data

CAS was performed in the left artery of 830 (48.82%) patients, the right artery of 860 (50.59%) patients, and bilaterally in 10 (0.59%) patients. Local anesthesia was used in 1504 (88.47%) patients. EPDs were used in 1595 (93.82%) CAS procedures. Balloon predilatation was used in 1403 (82.53%) procedures, balloon postdilatation in 103 (6.06%) procedures, and both predilatation and postdilatation in 88 (5.18%) cases. No balloon dilatation was used in 106 (6.24%) procedures. Self-expanding stents were used in 1683 (99.00%) CAS procedures, and in 479 (28.18%) cases, other cerebrovascular stents were placed during the same surgery (Table 2).

Table 2

Table 2

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Complication-related outcomes

Eleven patients experienced death and 31 patients experienced stroke within 30 days of surgery for a combined rate of death and stroke of 2.47%. Of the 11 deaths, nine were due to perioperative stroke considered hyperperfusion, one was due to MI, and one was due to pulmonary infection. As noted in Table 3, cerebral hemorrhage occurred in 10 patients, and 21 patients experienced cerebral infarction. One case of MI occurred, and the combined rate of MI, stroke, and death was 2.53%. The 30-day MI, stroke, and death rate progressively declined each year with the accumulation of operation experience (Figures 1 and 2). Scatter graph analysis was performed to examine the change in complication rate with increasing experience of the interventionalists (Figure 3A and 3B). A negative correlation between adverse event rates and number of patients was noted graphically and represented quantitatively by a linear regression with log transformation of both variables to better reflect the nature of the observation. The corresponding equation was lg(y) = 0.989-0.232×lg(x), with P=0.008, where y represents the stroke and death rate and x represents the number of patients. According to this analysis, the stroke and death rate is less than 3.5% after the interventionalist has performed more than 83 CAS procedures and less than 3.0% after the interventionalist has performed more than 161 CAS procedures.

Table 3

Table 3

Figure 1.

Figure 1.

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Univariate analysis

Table 4 presents the results of a univariate analysis of patient demographics and comorbidities, comparing patients who developed postoperative MI, stroke, and death with those who did not. Significant differences were associated with history of transient ischemic attack (TIA), symptomatic status, preoperative functional status (mRS), and statin use. Of 481 patients with a history of TIA, 18 (3.74%) developed postoperative MI, stroke, or death (P=0.045). Of 758 symptomatic patients, 30 (3.96%) developed postoperative MI, stroke, or death (P=0.001). Of 110 patients who had mRS ≥3, nine (8.18%) developed postoperative MI, stroke, or death (P <0.001). Of 1224 patients who were treated with statins preoperatively, 24 (1.96%) developed postoperative MI, stroke, or death (P=0.017).

Table 4

Table 4

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Multivariate analysis

Multivariate Logistic regression was carried out to determine preoperative risk factors for MI, stroke, and death (Table 5). The presence of symptoms (OR=2.485; 95% CI=1.267-4.876; P=0.008), history of TIA (OR=1.964; 95% CI=1.046-3.689; P=0.036), and mRS ≥3 (OR=3.025; 95% CI=1.353-6.763; P=0.007) were independent risk factors for postoperative MI, stroke, and death. In addition, statin use before surgery was an independent protective factor (OR=0.524; 95% CI=0.279-0.983; P=0.044).

Table 5

Table 5

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DISCUSSION

The efficacy and safety of CEA in the treatment of carotid artery stenosis have been confirmed.2,3,12 However, some carotid artery stenosis patients cannot receive CEA treatment due to operation risks and lesion localization. Generally, CAS offers the advantage of being minimally invasive. Based on the SAPPHIRE results, in 2004, the US Food and Drug Administration approved the first CAS for use in the United States for the treatment of extracranial carotid artery stenosis in patients at high risk for adverse events from CEA. CAS has been performed in increasing numbers, and many randomized trials (e.g., SAPPHIRE, EVA-3S, SPACE, and CREST) comparing CEA and CAS have been completed in order to determine their relative effectiveness and safety.9,10,13–15 CAS may be superior to CEA in certain patient groups, such as those who have had previous neck surgery or radiation injury. Recently, the CREST study reported that there were no significant differences between CAS versus CEA by symptom status for the periprocedural MI, stroke, and death rates.9 Therefore, CAS is effective and safe in the treatment of carotid artery stenosis, and CAS is considered an alternative treatment for carotid artery stenosis.

In this study, the 30-day postoperative MI, stroke, and death rate was 2.53%, and the 30-day postoperative death and stroke rate was 2.47%, which was better than that observed in other studies. Through earlier voluntary registries, the Global Carotid Artery Stent Registry16 included 12 392 CAS procedures in 11 243 patients performed at 53 sites between 1997 and 2002. The technical success rate was 98.9%, and the stroke or death rate was 4.7%. However, the Prospective Registry of Carotid Angioplasty and Stenting (Pro-CAS)17 included 3853 CAS procedures, with a technical success rate of 98% and a stroke and death rate of 2.8%. Recently, in a multicenter randomized trial, CREST, the periprocedural aggregate rate of stroke, MI, and death after CAS was 5.2%.9

EPDs were originally used as a protection factor for preventing infarction in procedures. However, at present the use of an EPD during CAS is optional and not without risk. The complexity of the procedure is increased when an EPD is used, and several unprotected steps are still present during device introduction and retrieval so that a number of microemboli reach the distal end.18 Although most studies reported that CAS was safer with the use of an EPD, Wholey et al16 reported 30-day stroke and death rates of 2.23% and 5.29% with an EPD and without an EPD, respectively (P <0.0001). In a multicenter review by Kastrup et al,19 2357 CAS procedures with the use of protection were compared with 839 procedures without protection. The combined stroke and death rate for cases with an EPD was 1.8%, and without protection this rate was 5.5%, which represented a significant difference (P <0.001). Retrospective analysis of the lead-in phase of the CREST showed a 4.9% 30-day risk of stroke without an EPD (n=81) versus 3.6% with an EPD (n=332, P=0.58).20 In this study, we observed a combined MI, stroke, and death rate of 2.32% for cases with an EPD and 5.71% for cases without protection, and this difference was not significant (P=0.068). Although no significant difference was observed in some studies, the stroke and death rate for cases with an EPD was lower than that without an EPD. Thus, there continues to be controversy regarding the benefit of these expensive devices.21

A number of studies have reported that the incidence of perioperative complications in symptomatic patients is higher than in patients without symptoms. In CAPTURE,22 compared with the asymptomatic cohort, symptomatic statistically patients had a significantly higher risk of 30-day MI, stroke, and death (12.0% for symptomatic vs. 5.4% for asymptomatic, P <0.05). The presence of symptoms was independently associated with adverse outcomes (OR=2.5; 95% CI=1.80-3.47; P <0.0001). In addition, the Pro-CAS trial reached the same conclusion with a perioperative stroke and death rate of 4.3% for symptomatic patients and 2.7% for asymptomatic patients (P <0.05). Experiencing symptoms was also independently associated with adverse outcomes (OR=1.54; 95% CI=1.1-2.1; P=0.008).17 Similarly, in this study, the rates of adverse outcomes in symptomatic patients were higher than those in asymptomatic patients. The 30-day MI, stroke, and death rate was 3.58% in symptomatic patients, but only 1.38% in asymptomatic patients (P=0.003), and having symptoms was independently associated with the 30-day MI, stroke, and death (OR=2.265; 95% CI=1.141-4.493; P=0.019).

In this study, we found that a history of TIA was independently associated with the 30-day MI, stroke, and death rate (OR=1.964; 95% CI=1.046-3.689; P=0.036). Aronow et al23 reported a similar finding of history of TIA as an independent risk factor (OR=3.11; 95% CI=1.19-8.09; P=0.020). Santaannop et al24 also supported this conclusion with univariate and multivariate analyses showing that a history of TIA increased the composite of MI, stroke, or death within 30 days after the intervention (P=0.03).

The number of studies investigating the effects of a preoperative severe neurological deficit on CAS outcome is still lacking. Among studies of CEA, several studies excluded the portion of patients considering benefit. In this study, the analysis showed that for patients with a mRS ≥3 during the procedural period, the MI, stroke, and death rates were significantly higher than those of patients with mRS <3 (7.34% vs. 2.02%, respectively, P=0.001), and multivariate analysis showed that mRS ≥3 is an independent risk factor for perioperative complications (OR=2.899; 95% CI=1.247-6.738; P=0.013). The patients with severe preoperative neurological deficits appeared to have large area cerebral infarction with disturbed cerebrovascular autoregulation and cerebral tissue damage, which lead to reperfusion easier.25 Therefore, detailed preoperative evaluation of neurological function is helpful to detect high-risk patients and plan treatments to prevent the complications.

Cerebrovascular disease patients taking statins have a reduced risk of stroke.26,27 The CAPTURE study22 found no association between statin use and perioperative stroke (OR=0.82; 95% CI=0.58-1.16; P=0.2711), whereas the study of Groschel et al28 found that the 30-day postoperative MI, stroke, and death rate of patients taking statins was significantly lower than that of patients who did not take statins (4% vs. 15%, respectively; P <0.05). Verzini et al29 demonstrated that statins significantly reduce the occurrence of perioperative stroke and death (OR=0.327; 95% CI=0.13-0.80; P=0.016). Similarly, in this study, the postoperative MI, stroke, and death was 1.88% for patients taking statins, whereas it was 3.59% for patients not taking statins (P=0.038). In the multivariate analysis, preoperative statin use was not associated with postoperative MI, stroke, and death (OR=0.560; 95% CI=0.291-1.077; P=0.082).

A learning curve for CEA was demonstrated by Archie.30 In the CAPTURE-2 study,31 a negative correlation between event rates and patient volume was noted graphically. In their later-phase single-arm study, they reported that a threshold of 72 cases was necessary for consistently achieving a death and stroke rate less than 3% in asymptomatic patients. In this study, the 30-day stroke and death rate progressively declined each year with the accumulation of operation experience. We found that the stroke and death rate was less than 3.5% once the interventionalist had performed more than 83 CAS procedures and less than 3.0% once the interventionalist had performed more than 161 CAS procedures. This study included both asymptomatic and symptomatic patients, and this is the reason that the effect of experience is higher than in the CAPTURE-2 study. However, all of the studies demonstrate the fact that a learning curve is present for CAS. The experience of the interventionalist plays a very important role in decreasing the stroke and death rate.

Our study has limitations. First, our data were collected retrospectively rather than gathered prospectively as in the clinical trials. Thus, the data may be less accurate than those gathered prospectively. Second, some other important variables that may influence the results were not considered.

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Keywords:

carotid artery stent; carotid stenosis; Chinese population; myocardial infarction; stroke; neurological deficit

© 2013 Chinese Medical Association