Abstract
Background
The usefulness of CASPER, a second-generation carotid stent, for carotid artery stenosis is becoming increasingly clear. However, few studies have directly compared treatment outcomes with those of the first-generation Carotid WALLSTENT. This study aimed to compare the outcomes of carotid artery stenting using CASPER and Carotid WALLSTENT for carotid artery stenosis performed at a single institution.
Methods
This retrospective study included 117 consecutive cases (Carotid WALLSTENT, 58 cases; CASPER, 59 cases) where carotid stent placement was performed for internal carotid artery stenosis between 2020 and 2021. Patient background, the presence or absence of ischemic complications as postoperative treatment outcomes, and the presence or absence of restenosis were extracted from the electronic medical records, and the results were compared between the Carotid WALLSTENT and the CASPER treatment groups.
Results
When comparing ischemic complications between the two groups, the treatment outcomes in the CASPER group were significantly better (Carotid WALLSTENT vs. CASPER: 6 (10.3%) vs. 2 (3.4%), respectively, p = 0.039). However, no significant difference in postoperative restenosis was observed between the two groups. Multivariate analysis revealed that using CASPER significantly reduced ischemic complications (odds ratio: 0.101, 95% confidence interval: 0.0117−0.878).
Conclusions
Carotid artery stenting using CASPER for internal carotid artery stenosis was associated with fewer ischemic complications than that with the Carotid WALLSTENT. No differences in treatment outcomes were observed with CASPER and Carotid WALLSTENT in terms of postoperative restenosis.
Keywords: Carotid artery stenting, CASPER, Carotid WALLSTENT, ischemic complication, restenosis
Introduction
The effectiveness of carotid artery stenting for preventing cerebral infarction caused by internal carotid artery stenosis has been demonstrated. 1 First-generation stents are characterized by a single-layer structure, and those available in Japan include the closed-cell type Carotid WALLSTENT™ (Boston Scientific, Santa Clara, CA, USA) and the open-cell types, including Protégé™ (Medtronic, Santa Rosa, CA, USA) and Precise™ (Cordis, Johnson & Johnson, Miami, USA). Closed-cell type stents are considered effective in preventing distal embolism by plaque in carotid artery stenosis caused by lipid-rich plaque owing to their mesh density, while open-cell type stents are characterized by their ability to press against blood vessels with high radial force in stenosis in areas with severe curvature. Recently, CASPER (Terumo, Japan), a second-generation stent characterized by a double-layer structure, has become available in Japan. 2 It consists of an outer layer stent braided with a nickel–titanium alloy wire and an inner layer stent. CASPER is a closed-cell type stent with high mesh density and small pore size among second-generation stents and reportedly suppresses plaque protrusion after stent placement. 3 Based on the difference in structure, we hypothesize that carotid artery stenting using CASPER would result in fewer ischemic complications associated with distal embolism, such as those caused by plaque protrusion. To verify this, we retrospectively compared the treatment outcomes of Carotid WALLSTENT, a closed-type conventional stent, with those of CASPER. Although many reports have been published on the effectiveness of CASPER, no studies have directly compared its therapeutic effects with those of the Carotid WALLSTENT. Here, we report the results of a retrospective comparison of the treatment outcomes of the carotid WALLSTENT and CASPER at a single institution.
Methods
Patient selection
This retrospective study included 117 consecutive patients who underwent carotid artery stent placement for internal carotid artery stenosis at our hospital between 2020 and 2021. Of the 117 cases, 58 patients underwent placement of the Carotid WALLSTENT, and 59 underwent placement of the CASPER. Cases up to October 2020 were performed using the Carotid WALLSTENT, while cases thereafter were performed using CASPER.
Procedure
Oral administration of aspirin (100 mg), clopidogrel (75 mg), or prasugrel (3.75 mg) was initiated at least 5 days before surgery. The effectiveness of antiplatelet drugs was assessed using VerifyNow (Accumetrics, San Diego, CA, USA). In cases of insufficient effectiveness, a boost of aspirin, clopidogrel, or prasugrel was administered according to the aspirin reaction units or P2Y12 reaction units.
All procedures were performed under general anesthesia. Procedures were generally performed via the femoral artery approach, but in three cases where problems were encountered with this approach, such as abdominal aortic aneurysm or femoral artery occlusion, surgery was performed via the brachial artery approach. The brachial artery approach was performed in two CASPER cases and one Carotid WALLSTENT case. An 11 cm 8F Super Sheath (Medikit, Tokyo, Japan) was placed in the femoral artery, and an 8F Guider soft tip (Stryker, Michigan, USA) was guided to the common carotid artery. After crossing the lesion using a 200-cm 0.0014 inch ASAHI CHIKAI (ASAHI Intecc, Aichi, Japan), a Spider FX (Medtronic, California, USA) was deployed as a distal embolic protection device through the internal carotid artery stenosis. In cases where the surgeon judged the stenosis to be severe, predilation was performed using a 5.0 mm × 40 mm Rx-Genity (Kaneka Medix, Tokyo, Japan). A 10 mm × 24 mm Carotid WALLSTENT or 10 mm × 20 mm CASPER (Terumo, Tokyo, Japan) was deployed to center the stenosis. After that, postdilation was performed using a 7.5 × 20 mm Rx-Genity, and the Spider was retrieved after confirming no no-flow or slow-flow. If no-flow or slow-flow was confirmed, the debris was collected using a suction device.
Evaluation method
Patient characteristics
Data such as patient age, sex, medical history, and smoking history were extracted from electronic medical records. Medical history included the presence or absence of hypertension, dyslipidemia, and diabetes. Cases where embolic infarction due to carotid artery stenosis was observed were judged to be symptomatic, and cases were classified as asymptomatic or symptomatic. Smoking history was divided into current, past, and never smokers.
Lesion evaluation
Radiological imaging was used to assess the lesions. Carotid artery stenosis was assessed using preoperative angiography. The degree of carotid artery stenosis was assessed using the North American Symptomatic Carotid Endarterectomy Trial (NASCET) method. 4 The presence or absence of ulcers in the stenotic portion of the carotid artery, the presence or absence of long lesions, and the left/right side were also evaluated. Long lesions were defined as stenoses measuring >2 cm. The plaque characteristics of the carotid artery were classified as high-, iso-, and low-intensity on T1-weighted carotid artery black-blood magnetic resonance imaging (MRI). The aorta was evaluated using preoperative cervical and thoracic magnetic resonance angiography (MRA). The aorta was classified into types 1–3 depending on its tortuosity. 5 In addition to the above type classification, the aorta was also evaluated to determine whether it was a bovine-type aorta.
Postoperative evaluation
The presence or absence of postoperative ischemic complications and hyperperfusion syndrome were evaluated. Ischemic complications were defined as any cerebral ischemic symptoms occurring within 30 days after surgery on the affected side. Hyperperfusion syndrome was defined as cranial nerve symptoms, cerebral hemorrhage, seizures, and headaches that were not due to ischemic lesions occurring within 1 week of surgery.
All patients underwent head MRI the day after surgery, and ischemic lesions were evaluated using diffusion-weighted imaging (DWI). Spot lesions causing high DWI signals were classified into <2 mm, 2−5 mm, and ≥5 mm, and the number of such spots was counted.
The presence or absence of cases where bradycardia or hypotension was caused by carotid sinus stimulation after surgery was extracted from electronic medical records. Cases where bradycardia or hypotension was caused by carotid sinus stimulation were defined as those requiring control with drugs, such as vasopressors or atropine.
Data were also extracted for cases that were followed up after surgery. Cases that were followed up using postoperative images were limited to patients who underwent carotid artery ultrasonography or angiography. Data on restenosis cases among those who were followed up after surgery were extracted. Restenosis was defined as a peak systolic velocity (PSV) of ≥300 cm/s, an end diastolic velocity of ≥140 cm/s, a PSV ratio between the internal carotid artery and the common carotid artery of ≥3.8, or a NASCET of ≥70%. 6 The secondary outcome was the modified Rankin scale (mRS) score 30 days after surgery.
Statistical analysis
Dichotomous variables are expressed as numbers and percentages. Continuous variables are expressed as means ± standard deviation. Odds ratios, 95% confidence intervals, and p values are presented for univariate and multivariate analyses. p < 0.05 was considered statistically significant. Differences between the two groups for dichotomous variables were examined using Fisher's exact test or the Chi-squared test. Differences between the two groups for continuous variables were examined using the Mann−Whitney U test or unpaired t-test. The factors contributing to ischemic complications were identified using univariate and multivariate analyses. GraphPad Prism 9 (San Diego, CA, USA) or EZR version 2.13.0 (Saitama Medical Center, Jichi Medical University, Omiya, Saitama, Japan) statistical software was used.
Results
Patient characteristics
Patient characteristics are summarized in Table 1. Patient characteristics were tabulated separately for the Carotid WALLSTENT and CASPER groups. Patient characteristics were compared between the two groups using p-values. Comparison of patient characteristics between the two groups showed significant differences in age (p = 0.039) and carotid plaque imaging (p = 0.0103).
Table 1.
Comparison of characteristics between the Carotid WALLSTENT and CASPER stent.
| Variables | Carotid WALLSTENT (n = 58) | CASPER stent (n = 59) | p-Value |
|---|---|---|---|
| Age (years) (mean ± SD) |
77.6 ± 8.9 | 74.3 ± 8.3 | 0.039 |
| Men (n [%]) | 49 (84.5) | 48 (81.4) | 0.807 |
| Medical history (n [%]) | |||
| Hypertension | 38 (65.5) | 41 (69.5) | 0.696 |
| Hyperlipidemia | 19 (32.8) | 20 (33.9) | 1.00 |
| Diabetes mellitus | 16 (27.6) | 13 (22.0) | 0.526 |
| Symptomatic | 40 (69.0) | 41 (69.5) | 1.00 |
| Smoking history (n [%]) | |||
| Current smoker and ex-smoker | 37 (63.8) | 34 (57.6) | 0.571 |
| Never smoker | 21 (36.2) | 25 (42.4) | |
| Stenosis characteristics (median [mean ± SD]) or (n [%]) | |||
| NASCET | 64.9 ± 18.7 | 63.8 ± 16.6 | 0.754 |
| Plaque imaging T1 BB | 0.0103 | ||
| High intensity | 35 (60.3) | 29 (49.2) | |
| Iso intensity | 17 (29.3) | 30 (50.8) | |
| Low intensity | 4 (6.9) | 0 (0.0) | |
| Ulceration | 17 (29.3) | 12 (20.3) | 0.29 |
| Long lesion | 11 (19.0) | 11 (18.6) | 1.00 |
| Left-sided | 31 (53.4) | 27 (45.8) | 0.462 |
| Aorta type (n [%]) | |||
| Type 1 aorta | 29 (50.0) | 31 (52.5) | 0.723 |
| Type 2 aorta | 18 (31.0) | 20 (33.9) | |
| Type 3 aorta | 11 (19.0) | 8 (13.6) | |
| Bovine-type aorta | 2 (3.4) | 5 (8.5) | 0.439 |
SD: standard deviation; NASCET: North American Symptomatic Carotid Endarterectomy Trial; BB: black blood.
Outcomes
Patient outcomes are summarized in Table 2. As with the patient background, the data were compiled by dividing the patients into Carotid WALLSTENT and CASPER treatment groups. Similarly, the results were compared using p values. The incidence of postoperative ischemic complications was significantly lower in the CASPER group (p = 0.039). All six cases of ischemic complications after Carotid WALLSTENT placement were mild strokes, but one patient had a worsening overall condition triggered by aspiration pneumonia. All ischemic complications after CASPER placement were mild strokes. There was no clear significant difference in the number of symptomatic patients between the CASPER and Carotid WALLSTENT groups (Table 1). Regarding the outcomes when classified into symptomatic and asymptomatic, only one asymptomatic patient in the CASPER placement group had a worsening mRS score, while no patient in the Carotid WALLSTENT group had a worsening mRS score. For symptomatic patients, there was no symptomatic patient in the CASPER placement group, while eight symptomatic patients in the Carotid WALLSTENT group had worsening mRS scores.
Table 2.
Comparison of clinical outcomes between the Carotid WALLSTENT and CASPER stent.
| Variables | Carotid WALLSTENT (n = 58) | CASPER stent (n = 59) | p-Value |
|---|---|---|---|
| Ischemic complication (mean ± SD) | 6 (10.3) | 2 (3.4) | 0.039 |
| Hyperperfusion syndrome (mean ± SD) | 2 (3.4) | 0 (0.0) | 0.807 |
| DWI spot area 1 day after operation | |||
| <2 mm (mean ± SD) | 2.4 ± 3.3 | 3.3 ± 4.0 | 0.236 |
| 2−5 mm (mean ± SD) | 3.1 ± 4.9 | 2.4 ± 3.4 | 0.968 |
| ≥5 mm (mean ± SD) | 1.0 ± 2.3 | 1.0 ± 2.5 | 0.791 |
| Brady or hypo pressure after operation (n [%]) |
10 (17.2) | 12 (20.3) | 0.814 |
| Follow-up case | N = 41 (70.7%) | N = 46 (78.0%) | |
| Months (mean ± SD) | 19.2 ± 17.4 | 22.7 ± 14.7 | 0.309 |
| Restenosis (n [%]) | 1 (2.4) | 1 (2.2) | 0.934 |
| mRS 30 days after operation | 0.361 | ||
| 0 | 28 | 31 | |
| 1 | 13 | 13 | |
| 2 | 3 | 7 | |
| 3 | 7 | 2 | |
| 4 | 6 | 6 | |
| 5 | 1 | 0 | |
| 6 | 0 | 0 |
SD: standard deviation; mRS: modified Rankin scale.
Analysis of ischemic complications
The factors contributing to ischemic complications were examined using univariate and multivariate analyses. Based on previous reports, patient background and factors thought to contribute to ischemic complications were selected as explanatory variables for the univariate and multivariate analyses. The results are summarized in Table 3. The multivariate analysis revealed that using CASPER significantly reduced the occurrence of ischemic complications.
Table 3.
Univariate and multivariate analyses for ischemic complications after CAS treatment.
| Variables | Univariate analysis | Multivariate analysis | ||||
|---|---|---|---|---|---|---|
| Ischemic complication+ (n = 8) | Ischemic complication- (n = 109) | p-Value | OR | 95% CI | p-Value | |
| Age >75 years | 2 (25.0) | 49 (45.0) | 0.463 | 0.975 | 0.127−7.5 | 0.98 |
| NASCET > 60 | 2 (25.0) | 51 (46.8) | 0.29 | 8.77 | 0.97−79.3 | 0.0532 |
| Plaque image | 0.791 | |||||
| High | 4 (50.0) | 60 (55.0) | ||||
| Iso | 4 (50.0) | 43 (39.4) | 1.83 | 0.262−12.8 | 0.542 | |
| Low | 0 (0.0) | 4 (3.7) | 2.03e-08 | 0−inf | 0.998 | |
| Smoking history | 0.403 | |||||
| Current smoker | 1 (12.5) | 21 (19.3) | ||||
| Past smoker | 1 (12.5) | 48 (44.0) | 1.38 | 0.0611−31.2 | 0.84 | |
| Never smoker | 6 (75.0) | 40 (36.7) | 12.8 | 0.781−211 | 0.074 | |
| Aorta type | 0.0634 | |||||
| Type 1 | 5 (62.5) | 55 (50.5) | ||||
| Type 2 | 0 (0.0) | 38 (34.9) | 8.12e-09 | 1−inf | 0.994 | |
| Type 3 | 3 (37.5) | 16 (14.7) | 1.70 | 0.227−12.7 | 0.607 | |
| CAS type | 0.163 | |||||
| Carotid WALLSTENT | 6 (75.0) | 52 (47.7) | ||||
| CASPER | 2 (25.0) | 57 (52.3) | 0.101 | 0.0117−0.878 | 0.0377 | |
CAS: carotid artery stent; OR: odds ratio; CI: confidence interval; NASCET: North American Symptomatic Carotid Endarterectomy Trial.
ORs were calculated for CASPER with the Carotid WALLSTENT as the control. The multivariate analysis was performed using age, NASCET, plaque image, smoking history, aorta type, and CAS type as the explanatory variables.
We evaluated the DWI high-signal areas on postoperative MRI. The number of DWI high signals was significantly higher in patients presenting with ischemic complications (ischemic complication- vs. ischemic complication-: 6.4 vs. 19.6, p = 0.0006, Figure 1). When comparing the size of DWI hyperintensities, patients with ischemic complications had a higher number of DWI hyperintensities, especially at 2–5 mm (ischemic complication vs. ischemic complication-: 2.2 vs. 10.1, p < 0.0001; Figure 2). Although there was no statistically significant difference in terms of the type of stent, the number of DWI hyperintensities <2 mm was higher in the CASPER group, while the number of DWI hyperintensities 2–5 mm was higher in the Carotid WALLSTENT group (Figure 3).
Figure 1.
Comparison of the number of DWI hyperintensities between groups with and without ischemic complications. DWI: diffusion-weighted imaging.
Figure 2.
Comparison of the number of DWI hyperintensities by size between groups with and without ischemic complications (A: <2 mm, B: 2−≤5 mm, C: ≥5 mm).
Figure 3.
Comparison of the number of DWI hyperintensities by size between the Carotid WALLSTENT and the CASPER groups (A: <2 mm, B: 2−≤5 mm, C: ≥5 mm).
Representative case
A 78-year-old man was diagnosed with asymptomatic left-sided internal carotid artery stenosis at a local hospital. His medical history included anxiety neurosis, chronic kidney disease, diabetes, and hypertension. Cervical MRA showed type 2 aorta (Figure 4(a)). T1-weighted carotid artery black-blood MRI showed high intensity in the plaque area, suggesting unstable plaque (Figure 4(b)). Carotid artery angiography revealed approximately NASCET 50% stenosis at the origin of the right internal carotid artery (Figure 4(c)), and a Carotid WALLSTENT 10 mm × 24 mm was placed (Figure 4(d)). A head MRI performed the day after the operation showed scattered DWI with high signal intensity in the left cerebral hemisphere, suggesting acute infarction (Figure 4(e) and (f)). After the operation, slight paralysis was observed in the right upper and lower limbs. The symptoms improved with rehabilitation, and the patient was discharged on the 23rd day.
Figure 4.
(A) Cervical MRA image showing type 2 aorta. (B) T1-weighted carotid artery black-blood MRI showing high intensity in the plaque area, suggesting unstable plaque. (C) Carotid artery angiography shows approximately NASCET 50% stenosis at the origin of the right internal carotid artery. (D) Placement of a Carotid WALLSTENT 10 mm × 24 mm. (E, F) Head MRI performed the day after the operation showing scattered DWI with high signal intensity in the left cerebral hemisphere, suggesting acute infarction. MRA: magnetic resonance angiography; MRI: magnetic resonance imaging; NASCET: North American Symptomatic Carotid Endarterectomy Trial; DWI: diffusion-weighted imaging.
Discussion
In this study, we compared the treatment outcomes of Carotid WALLSTENT and CASPER in patients who underwent carotid artery stenting for carotid artery stenosis. In a retrospective comparison of the treatment outcomes of stents used in conventional carotid artery stenting, it was difficult to make a complete comparison because of the differences in embolic protection devices (EPD) and the devices used for postdilation. A previous randomized trial comparing CASPER and closed stents did not report superior treatment outcomes with CASPER. 7 This was because various factors are involved in carotid stent placement, making it difficult to simply compare stent devices. In our study, although the types of stents used differed, EPD was limited to a Spider FX, a filter, and a 7 mm × 40 mm Genity RX was used for postdilatation. As similar devices were used, it is believed that accurate comparisons of postoperative complications can be made with those in previous studies.
The use of CASPER was found to significantly reduce ischemic complications compared with that after Carotid WALLSTENT. We found that cases with ischemic complications were particularly large, particularly in the postoperative DWI high-intensity spots measuring 2–5 mm. Furthermore, when comparing the postoperative ischemic lesions between the Carotid WALLSTENT and CASPER groups, although no significant difference was observed, the Carotid WALLSTENT group had more ischemic spots measuring 2–5 mm in size. When comparing the free cell areas of Carotid WALLSTENT and CASPER, the free cell area of Carotid WALLSTENT is <2.5 mm2, while that of CASPER is 375 um, and the free cell area of CASPER is clearly smaller.8,9 In contrast, the mesh size of Spider varies in the range of 50−200 um. When CASPER is deployed, the debris is predicted to be ≤375 um; therefore, it is highly likely that the plaque can be captured by Spider. However, it cannot be denied that debris that passed through the Carotid WALLSTENT could not be captured by Spider and scattered distally, resulting in a relatively large ischemic focus that became symptomatic. These findings suggest that the low pore density of CASPER significantly reduces ischemic complications.
Although no significant difference was observed, a NASCET score of ≥60 tended to be associated with a high incidence of ischemic complications in the multivariate analysis. At our facility, we use Spider FX to prevent distal embolism; however, when we first crossed the lesion with a microguidewire, we could not prevent the distal embolism with an EPD. An ischemic focus may be created during this lesion crossing, and the higher the degree of stenosis during lesion crossing, the higher the probability of emboli being sent to the distal area. However, no correlation was found between plaque characteristics and the ischemic focus. Lipid-rich plaques are generally prone to distal embolism. 10 However, both CASPER and Carotid WALLSTENT are closed-cell type stents and have a strong ability to suppress lipid-rich plaques, suggesting no difference in their effectiveness.
CASPER is highly effective in preventing distal embolism but has been reported to cause a high rate of restenosis.2,3,11,12 Our results showed no clear difference compared to the Carotid WALLSTENT. A previous report has suggested that if the contact between the inner and outer layers of the CASPER is weak, bidirectional intimal proliferation occurs between these two layers, resulting in postoperative stenosis. 2 At our institution, we use a relatively large percutaneous transluminal angioplasty balloon of 7 mm for postdilatation. We speculate that this improves the contact between the inner and outer layers, which may reduce restenosis; however, further analysis is required.
This study had several limitations. First is the single-center retrospective study design. Larger multicenter prospective studies are necessary to validate the results of this study. Second, in our facility, we did not adjust the size of the stent according to the thickness of the carotid artery, and we used Carotid WALLSTENT 10 mm × 24 mm and CASPER 10 mm × 20 mm in all cases. Although we confirmed that the stent covered the stenotic area in all cases, we have not fully verified the ischemic complications that may occur due to the difference in size. Third, there were variations in follow-up between the Carotid WALLSTENT and the CASPER groups. In our hospital, the follow-up period after carotid stent placement and the follow-up modalities, such as whether to use carotid echo or cerebral angiography, are at the discretion of the attending outpatient physician. In this study, follow-up was not performed in approximately 30% of cases, so we cannot deny the possibility that potential cases of restenosis may have been overlooked. Additionally, the standard deviation of the follow-up period varied, so late-stage ipsilateral ischemic complications may have been hidden due to this difference.
Conclusions
Carotid artery stenting using CASPER for internal carotid artery stenosis has fewer ischemic complications than that with Carotid WALLSTENT. No significant difference in postoperative restenosis was observed between patients who received CASPER and Carotid WALLSTENT.
Footnotes
Data availability statement: All supporting data are available from the corresponding author upon reasonable request.
The authors declared no potential conflicts of interest with respect to the research, authorship, and/or publication of this article.
Ethical approval and informed consent statement: This study was approved by the Institutional Ethics Committee of our hospital. As this was a retrospective study and all data were anonymized, informed consent from eligible patients was obtained using the opt-out method.
Funding: The authors received no financial support for the research, authorship, and/or publication of this article.
ORCID iDs: Takashi Fujii https://orcid.org/0000-0002-2551-1144
Kosuke Takigawa https://orcid.org/0000-0003-4393-1721
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