Purpose Mechanical thrombectomy (MT) is a proven method to treat large vessel occlusions in acute anterior circulation stroke. We compared the technical, imaging, and clinical outcomes of MT performed with either TREVO or Capture LP devices.
Methods There were 42 and 43 patients in the TREVO and Capture LP groups, respectively. Baseline variables, technical outcome (Thrombolysis In Cerebral Infarction, TICI), 24 hours imaging outcome, and 3-month clinical outcome (modified Rankin Scale, mRS) were prospectively recorded. The patients were stratified according to clot location, groups compared, and logistic regression models devised to study the effect of device selection on the clinical outcome.
Results The technical success rates were equal in both proximal (internal carotid artery and proximal M1 segment) and distal occlusions (distal M1 and M2 segments). The proportion of TICI 2b or 3 was 96% and 87% with TREVO and 87% and 89% with Capture LP (p=0.25 and p=0.80, respectively). Device selection did not significantly predict good clinical outcome (mRS ≤2) in either proximal or distal occlusions. In multivariate analysis, selecting Capture LP borderline significantly increased the odds of an excellent outcome close to sixfold both in proximal and distal occlusions (OR 6.7, 95% CI 0.82 to 53.7, p=0.08 and OR 5.7, 95% CI 0.88 to 37.8, p=0.07, respectively).
Conclusions TREVO and Capture LP perform equally well in proximal and distal occlusions in the anterior circulation when technical and good clinical outcome are considered. Capture LP may have a small advantage in reaching mRS ≤1 at 3 months. However, this needs to be confirmed in a randomized study.
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Recent randomized studies have established the efficacy and safety of mechanical thrombectomy (MT) as treatment for acute anterior circulation stroke in patients having a proximal vessel occlusion with substantial penumbra in perfusion imaging, a reasonably small infarct core, and adequate collateral circulation.1–5
There are a number of newer generation retrievable stent-based MT devices in the market. Among the more popular of these systems are TREVO ProVue (Stryker Neurovascular/Concentric Medical, Mountain View, California, USA) and Capture LP (eV3/ Covidien/Medtronic, Santa Rosa, California, USA). However, currently only a few studies have compared the different retrievable stent systems.
The TREVO Retriever is a thrombectomy device designed to optimize the integration of the clot, especially in intracranial proximal large vessel occlusions. It is a retrievable, hydrophilic coated, closed cell stent-like system. This device has conventional stent characteristics with optimized orientation of the struts, which aims at better thrombus incorporation. Capture LP is a laser-cut stent attached to a nitinol wire. The device is specially designed to fit in smaller microcatheters to allow thrombectomy in distal and more tortuous vessels.
Our study aimed to compare the efficacy and safety of two different newer generation stent retriever devices with different target vessel profiles—the TREVO Retriever and Capture LP—in the treatment of both proximal and distal occlusions in the anterior circulation.
Overview, participants and variables
We prospectively collected and analyzed the clinical and imaging data of 130 consecutive patients who were admitted to Tampere University Hospital between January 2013 and December 2014 with acute ischemic stroke. Patients underwent clinical and imaging evaluation and proceeded to digital subtraction angiography with an intention to perform MT. The inclusion criteria for this study were occlusion of the internal carotid artery (ICA) and/or middle cerebral artery and MT with either TREVO or Capture LP. These criteria were met by 85 patients and 45 patients were excluded. Eight were excluded because they had posterior circulation stroke and one patient had an occlusion of the A3 segment of the anterior cerebral artery. In 15 cases thrombectomy with a stent retriever device was not performed either because the clot had dissolved, there was no access to the thrombus, or only aspiration thrombectomy was done. In 10 patients more than one device type was used and in 11 cases the device used was neither TREVO nor Capture LP.
The initial imaging evaluation consisted of non-contrast-enhanced CT (NCCT), CT angiography (CTA), and CT perfusion (CTP). The selection of patients as candidates for MT was based on absence of extensive irreversible ischemic changes and hemorrhage in NCCT, evaluation of the amount of salvageable tissue in CTP imaging and clot position in CTA. ICA or proximal M1 segment occlusions were defined as proximal and distal M1 and M2 segment occlusions as distal occlusions. Patients who were referred to our institution from another hospital were re-evaluated with at least NCCT and CTA upon arrival before proceeding to the angiographic suite. In the case of wake-up strokes, CTP was performed if no large infarct was seen in NCCT.
Baseline clinical characteristics included age, sex, time from symptom onset to imaging and to the initiation of intravenous thrombolysis (IVT), and clinical risk factors for ischemic stroke (hypertension, diabetes, coronary heart disease, atrial fibrillation). These data were collected from the patient records. The National Institutes of Health Stroke Scale (NIHSS) score at presentation, time from symptom onset to imaging and to recanalization of the occluded vessel, duration of the procedure, Thrombolysis in Cerebral Infarction (TICI) grading, and possible intraprocedural complications had been prospectively stored in a specifically devised questionnaire. A follow-up NCCT was performed 24 hours after MT. Hemorrhagic complications and post-infarct edema were classified according to SITS-MOST criteria.6 The primary clinical outcome measure was the modified Rankin Scale (mRS), evaluated by a neurologist 3 months after the stroke based on a follow-up visit or a telephone interview.
IVT (Actilyse 0.9 mg/kg, Boehringer-Ingelheim, Ingelheim, Germany) was administered as bridging therapy based on the judgment of the attending stroke neurologist and possible contraindications. According to the literature, IVT prior to MT is associated with a better clinical outcome.7 ,8 The Actilyse bolus was given on the CT table. In one case an eligible patient did not receive the bolus because the onset to imaging time was less than 30 min and the patient was transferred directly to the angiographic suite. Patients coming from an outside hospital received IVT according to the drip-and-ship protocol. The Actilyse drip was continued until groin puncture. MT was performed using a biaxial system consisting of a 8 Fr guiding catheter with a tip balloon and coaxially a 0.021 inch microcatheter or a triaxial system consisting of a 8 Fr guiding catheter with a tip balloon, a distal access catheter through which a microcatheter was inserted with the aid of a 0.014 inch microguidewire. The microcatheter was navigated through the occluded segment of the artery and a suitable stent retriever device was positioned through the microcatheter to the site of the thrombus and deployed. The stent was left in place for up to 3 min and then retrieved and, at the same time, the guiding catheter or the intermediate catheter was aspirated forcefully. The same procedure was repeated until satisfactory circulation was restored. Two experienced (>5 years) neurointerventional radiologists (JS and J-PP), who had been trained to use both devices, performed the interventions. The selection of the device was eventually based on the preference of the operator. However, during half of the study time one device was the first choice over the other, during which periods 83% of the MTs were performed with TREVO and 84% with Capture LP, respectively. The TREVO device has been used for longer in our institution and the Capture LP device was available from spring 2013. This was why TREVO was the predominant device used in the earlier half of the investigation. Furthermore, it appears that Capture LP was preferred for more distal locations due to its lower profile which enables it to fit in smaller microcatheters. We used 4 mm×20 mm TREVO and 3 mm×23 mm or 4 mm×23 mm Capture LP devices.
Imaging parameters and image analysis
Details are given in online supplement 1.
The data were analyzed with SPSS V.23 (SPSS, Chicago, Illinois, USA). Group comparisons were performed using the Student t test, the χ2 test, Fisher exact test, and the Mann-Whitney U test. Patients with a collateral score of 2–4 were regarded as having good collateral vessel filling. Patients who had 3-month mRS ≤2 were considered to have experienced a good clinical outcome and those with mRS ≤1 an excellent clinical outcome. Binary logistic regression modeling using these two outcome measures and mortality as the dependent variables was repeated for different variables of interest. Admission NIHSS, age, sex, time from onset to recanalization, clinical risk factors of stroke, device selection, cerebral blood volume (CBV) Alberta Stroke Program Early CT Score (ASPECTS) at admission, site of the occlusion and collateral score were examined as potential confounders and were first tested in univariate models with the dependent variables described above. Based on these results, multivariate models were devised. OR with 95% CI was calculated for each covariate. The calibration of the models was evaluated with the Hosmer-Lemeshow test and discrimination with the C statistic.
Population and baseline characteristics
The inclusion criteria were met by 85 patients with 42 patients (49%) in the TREVO group and 43 patients (51%) in the Capture LP group. In the TREVO group 27 (64%) patients had a proximal thrombus compared with 15 (35%) in the Capture LP group (p=0.007, figure 1). There was a significantly larger number of ICA occlusions in the TREVO group (19 vs 6, p=0.002) whereas there were more M2 occlusions in the Capture LP group (5 vs 15, p=0.01).
The main baseline and admission imaging characteristics are summarized for the whole population by device type and according to the site of the occlusion (proximal or distal) in tables 1 and 2. Nevertheless, in two cases NIHSS could not be scored reliably because the paramedic crew had sedated the patient during transportation. In six cases the time of the onset of the symptoms was unknown (ie, they were wake-up strokes). CTP was successfully completed in 60 of the 85 patients (71%), of which 25 were in the TREVO group (60%) and 35 in the Capture LP group (81%). In one case the 24-hour control imaging was not available and in three cases the exact duration of the procedure had not been recorded. In addition, one patient could not be reached by telephone or by other means for the 3-month mRS assessment. The differences between the groups in age, sex or other established stroke risk factors, NIHSS at admission, NCCT ASPECTS at admission, or the collateral circulation evaluated from admission CTA images were not significant. However, there was a non-significant trend towards more patients in the TREVO distal occlusion group being older and having coronary artery disease, atrial fibrillation, diabetes, larger clot burden and, correspondingly, worse collateral circulation and larger perfusion defects in the mean transit time (MTT) maps compared with the Capture LP distal occlusion group (table 2). Overall, the size of the perfusion defect in the CBV maps was borderline significantly larger in the TREVO group (ASPECTS 7 vs 9, p=0.07), but this trend was not seen when the proximal and distal occlusions were studied separately (tables 1 and 2). There were no significant differences in onset to imaging times in any of the three comparisons. Fifty-four patients (64%, 28 vs 26, p=0.55) received IVT before MT. IVT did not have a statistically significant impact on the 3-month clinical outcome. Otherwise, we noticed a trend towards good clinical outcome among patients treated with IVT compared with those not treated (34 vs 15, p=0.16).
Patients in the TREVO group had more proximal occlusions and a correspondingly significantly larger overall clot burden (p=0.004, table 1) and borderline significantly larger clot burden score (CBS) in the distal occlusion group. However, these differences were not reflected in technical success as measured by TICI (figure 2) or the duration of the procedure (33 vs 32 min, p=0.79, table 1). The technical outcome was TICI 2b or 3 in 77 out of 85 cases (91%, table 1) and there was no significant difference between the groups (93% vs 88%, p=0.48). Furthermore, there was no significant difference in the onset to recanalization times (229 min vs 243 min, p=0.55, table 1). When proximal and distal occlusions were studied separately, no significant differences were found between the devices in these three parameters (table 2).
Imaging and 3-month clinical outcomes
The distribution of the 3-month clinical outcome measured with mRS in the TREVO and Capture LP proximal and distal occlusion groups is shown in figure 3. Overall, 50 of the 85 patients (60%) had a favorable clinical outcome (mRS ≤2) at 3 months with no significant difference between the groups in any comparisons (tables 1 and 2). There was a trend towards more patients having an excellent outcome (mRS ≤1) in the Capture LP group in all comparisons (overall: 32% vs 49%; proximal occlusions: 39% vs 60%; distal occlusions: 20% vs 57%; p=0.11–0.19) and higher overall mortality in the TREVO group (17% vs 5%, p=0.07, tables 1 and 2). In accordance, patients undergoing surgery with TREVO had larger infarct volumes at 24 hours, a larger number of hemorrhagic complications, and significantly more severe post-infarct edema overall and in the distal occlusion group. No such significant differences or trends were found in the proximal occlusion group (tables 1 and 2). All major space-occupying hemorrhages were symptomatic with three occurrences (8%) in the TREVO group and one (2%) in the Capture LP group. One bleeding in the TREVO group was due to perforation of a lenticulostriate perforant artery during catheterization. In addition, we incurred one unintended device detachment with Capture LP.
In a binary logistic regression multivariate model with mortality as the dependent variable and device selection, CBV ASPECTS at admission, NIHSS at admission, age, site of the occlusion (ICA vs non-ICA) and collateral score as covariates, CBV ASPECTS was the only significant predictor of mortality with each point increment decreasing the odds of dying by 0.59 (OR 0.59, 95% CI 0.36 to 0.97, p=0.04). When excellent outcome (mRS ≤1) was chosen as the dependent variable, the site of the occlusion, good collateral circulation, and the use of Capture LP statistically significantly predicted an excellent outcome (see online supplementary table 1). Admission NIHSS and CBV ASPECTS were left out of the model because they were not significant predictors in univariate analysis. Age was kept in the model for theoretical reasons. These three statistically significant variables were also the result of backward likelihood ratio method when all the six covariates of the first model were given as input. The use of Capture LP increased the odds of an excellent outcome fivefold (OR 5.2, 95% CI 1.5 to 15.3, p=0.008). When good clinical outcome (mRS ≤2) was chosen as the dependent variable instead, the device used was not a significant predictor. Regression models were devised with similar principles separately for proximal and distal clot locations (tables 3 and 4). In both these models device selection was a borderline significant predictor of an excellent outcome (p=0.08 and p=0.07, respectively).
MT with a stent retriever is an effective method to treat acute ischemic stroke in patients with a proximal vessel occlusion.1–5 ,9 The superiority of newer generation devices over the older ones in efficacy and safety has been established in previous studies.10–12 These newer generation devices have differing design features that potentially make them more suitable to certain anatomies and occlusion sites, as demonstrated in a recent article on stent retriever mechanical properties and effectiveness.13
In this report the radial force, radial pressure variation, and ability of the stent to adhere to the vessel wall during the retrieval were evaluated. The TREVO and Capture LP devices had comparable radial forces in small sizes and both experienced loss of contact with the vessel wall during retrieval. TREVO 4 mm×20 mm had a somewhat higher radial force, but during retrieval the authors observed severe loss in radial force and elongation of the device around angulated vessels.
We found only two studies in the literature that directly compared different newer generation stent retriever thrombectomy devices. Roth et al14 conducted an experiment in a porcine model to compare Solitaire AB/FR and Aperio. They did not find any significant differences in the technical success rate or number of complications between the two devices. Another study compared, in a retrospective non-randomized set-up, the TREVO and Solitaire AB/FR devices.15 There was a trend towards a larger number of symptomatic intracerebral hemorrhages in the Solitaire group (4 vs 0), but the difference was not statistically significant in this small population (n=22). Otherwise, no differences were found in either different aspects of technical success or clinical outcome. Zaidat et al16 compared the results of two post-marketing registries and found that the clinical performance of TREVO was comparable to that of Solitaire AB/FR.
In our study no statistically significant differences were found between the TREVO and Capture LP groups in terms of age, sex, or the other established stroke risk factors. However, in the TREVO distal occlusion group there was a non-significant trend towards more patients being older and having more stroke risk factors and unfavorable admission imaging findings. Technical outcome was equivalent in the two cohorts in terms of recanalization results and procedure durations, even though there were more ICA occlusions and thus a higher clot burden in the TREVO group. The technical outcomes were also similar when proximal and distal occlusions were considered separately. This suggests that, despite different target vessel profiles by design, the devices perform similarly in large and medium sized vessels. As a general observation, the higher clot burden of the more proximal occlusions does not seem to convert into longer procedure times. This may be because of the extra time needed for more distal catheterizations and the more tortuous anatomy distally, which make both the withdrawal of the deployed device and aspiration technically more challenging.17
The 3-month clinical outcome was similar in both groups when functional independence (mRS ≤2) was considered. However, in univariate analyses there was a trend towards more patients having an excellent outcome (mRs ≤1) in the Capture LP group and higher mortality in the TREVO group, both overall and in different clot locations. These findings are probably in part due to larger perfusion defects in the admission CBV maps in the proximal occlusions, differences in stroke risk factors between the groups in the distal occlusions (older age, larger proportion of patients with coronary artery disease, atrial fibrillation and diabetes in the TREVO group), and consequently larger infarct volumes at 24 hours, more hemorrhagic complications and significantly more severe post-infarct edema. However, in multivariate analyses the device selection remained a significant or borderline significant predictor of excellent outcome. In the distal clot locations this may reflect actual superiority of the Capture LP device because it is specifically designed in terms of the size and flexibility of the system components to enable MT of more distal clots. However, only six patients in the TREVO group had an M2 occlusion, which inherently has a higher potential for excellent 3-month clinical outcome, which adds uncertainty to the findings. Yet, the same trend was also observed in the proximal occlusions in both univariate and multivariate analyses.
There was one case of mechanical failure with Capture LP, which led to permanent stent placement. There were no vessel perforations related to withdrawal of a deployed device.18
The major limitation of our study is the non-randomized design. Because of this there were significantly more ICA occlusions in the TREVO group and M2 occlusions in the Capture LP group. This difference in the selection of the device is probably due to operator preference and driven by device properties—namely, the sizes available at the time, flexibility, trackability, pushability, and maneuverability. This bias was controlled for by stratification based on clot location and by using multivariate techniques. The assignment of first choice periods in the device selection during which 83% of the procedures were performed with the TREVO device and 84% with the Capture LP device, respectively, further offsets the bias. Another limitation was the somewhat small study population, which decreases the value of subgroup analyses.
In conclusion, TREVO and Capture LP perform equally well in proximal and distal occlusions in the anterior circulation when technical and good clinical outcome are considered. Capture LP may have a small advantage in reaching mRS ≤1 at 3 months. However, this needs to be confirmed in a randomized study or comparisons of large multicenter registries.
We thank Jari Hakomäki for image interpretation.
Contributors Planning: SP, HN, NS. Conduct: JS, J-PP, IM, JO, SP, NS. Reporting: SP, NS.
Funding This study was financially supported by the Competitive State Research Financing of the Expert Responsibility Area of Tampere University Hospital (grant 9S061).
Competing interests None declared.
Ethics approval University of Tampere scientific board.
Provenance and peer review Not commissioned; externally peer reviewed.