Skip main navigation

Impact of Stent Retriever Size on Clinical and Angiographic Outcomes in the STRATIS Stroke Thrombectomy Registry

Originally publishedhttps://doi.org/10.1161/STROKEAHA.118.022987Stroke. 2019;50:441–447

Abstract

Background and Purpose—

The safety and efficacy of mechanical thrombectomy in patients with acute ischemic stroke has been demonstrated. However, the impact of stent retriever size on clinical and angiographic outcomes is not well established.

Methods—

This was a retrospective ad hoc analysis of data from the STRATIS (Systematic Evaluation of Patients Treated With Neurothrombectomy Devices for Acute Ischemic Stroke) registry—a prospective, multicenter study of patients with large vessel occlusion treated with the Solitaire stent retriever. An independent core laboratory, blinded to clinical outcomes, reviewed all procedures and angiographic data to classify stent retriever size, targeted clot location, recanalization after each pass, and the number of stent retriever passes. The primary angiographic end point was first-pass effect (FPE) as determined by a core laboratory and defined as achieving near-complete revascularization (modified Thrombolysis in Cerebral Infarction ≥2c) after the first pass without the use of rescue therapy. Rates of modified FPE were also assessed, defined as meeting all criteria for FPE but achieving modified Thrombolysis in Cerebral Infarction ≥2b after first pass. The primary clinical end point was functional independence (modified Rankin Scale, 0–2) at 3 months as determined on-site. Outcome comparisons were made across the stent retriever size groups and adjusted for baseline characteristics.

Results—

Of 715 patients, a 4×20 stent retriever was used in 201 (28%) patients, 4×40 was used in 270 (38%) patients, and 6×30 was used in 244 (34%) patients. The 4×40 group had the highest rate of FPE (P=0.003 versus 6×30) and modified FPE (P=0.038 versus 4×20; P=0.0001 versus 6×30). Final revascularization was not significantly different across the groups, and there were no significant differences in functional dependence or mortality at 90 days post-procedure. Use of the longer stent retriever (4×40) was an independent predictor of achieving modified FPE (P=0.037 versus 6×30; P=0.037 versus 4×20).

Conclusions—

The longer stent retriever (4×40) demonstrated the highest rate FPE and modified FPE compared with larger diameter or shorter stent retrievers, suggesting that their routine use may improve early revascularization success.

Clinical Trial Registration—

URL: https://www.clinicaltrials.gov. Unique identifier: NCT02239640.

Introduction

Mechanical thrombectomy has been demonstrated as an effective therapeutic intervention for acute ischemic stroke secondary to large vessel occlusion.1–7 The American Heart Association/American Stroke Association guidelines now recommend the use of stent retrievers for mechanical thrombectomy within 8 hours of symptom onset7 because large vessel occlusions often respond poorly to intravenous tPA (tissue-type plasminogen activator).8 However, ≤30% to 65% of patients remain physically disabled after intervention with stent retrievers.1–6

Recently, stent retrievers with smaller diameter and shorter length have been associated with higher rates of adverse events,9,10 suggesting that the size of the stent retriever may influence patient outcomes; although a large multicenter retrospective study reported no such effect.11 Indeed, preclinical studies have demonstrated that soft clots have a tendency to fragment or protrude through stent12,13 and that large stents (>6 mm in diameter) better capture the clots compared with smaller stents.13 Additionally, a recent retrospective institutional analysis comparing equal-diameter (4 mm) stent retrievers reported that longer stent retrievers (40 mm) enhance thrombectomy performance compared with shorter 20-mm retrievers.10 Thus, the theoretical advantage that longer stent retrievers provide is the larger surface area of interaction with the thrombus to reduce the risk of leaving clot fragments behind.10

In this study, we evaluated the influence of operator choice of stent retriever size in the STRATIS study (Systematic Evaluation of Patients Treated With Neurothrombectomy Devices for Acute Ischemic Stroke)14—the largest Solitaire (Medtronic, Irvine, CA) stent retriever treatment registry, with independent imaging and technical core laboratories blinded to the clinical outcomes.

Methods

Study Design and Inclusion Criteria

Key Inclusion Criteria

All supporting data from this study are available within the article and corresponding online-only Data Supplement. This study represents a retrospective ad hoc analysis of data collected from the STRATIS registry. STRATIS was a prospective, multicenter, nonrandomized, observational registry evaluating the use of Solitaire revascularization devices (Solitaire; Medtronic) and MindFrame Capture Low Profile revascularization devices (MindFrame; Medtronic) in 1000 patients experiencing an acute ischemic stroke because of large vessel occlusion at 55 US centers between August 2014 and June 2016 with approval from local institutional review boards. The primary methods and results of the STRATIS registry have been published previously.14 Briefly, the key inclusion criteria were (1) confirmed, symptomatic large vessel occlusion; (2) use of Medtronic market-released neurothrombectomy device as the initial device for thrombus removal; (3) <8 hours between stroke symptom onset and femoral puncture; (4) premorbid modified Rankin Scale score ≤1; and (5) pretreatment National Institutes of Health Stroke Scale score of 8 to 30. The technical approach, including the use of a balloon guide catheter or intermediate large bore catheter, as well the choice of stent size, were not compulsory and were up to the treating neurointerventionalist's choice. STRATIS is registered with https://www.clinicaltrials.gov as NCT02239640.

In this prespecified subgroup analysis, subjects were excluded because of (1) missing technique core laboratory assessment (n=7), (2) posterior circulation occlusions (n=45) because large-diameter stent retrievers are less likely to be used in these cases, 3) proximal carotid lesions (n=123), (4) intracranial atherosclerotic lesions (n=26), (5) use of MindFrame stent retriever device (n=28), (6) use of 4×15 or 6×20 from the stent retriever size comparison (n=18), owing to small sample size, or (7) unspecified Solitaire size (n=26; Figure 1). Patient consent was obtained no later than 7 days after hospital discharge.

Figure 1.

Figure 1. Study flowchart. Some patients met multiple exclusion criteria, and hence individual category n do not sum to total of exclusions.

All imaging and angiographic data were centrally collected and interpreted by the independent STRATIS imaging and angiography core laboratory for modified Thrombolysis in Cerebral Infarction (mTICI) and the Alberta Stroke Program Early CT Score (ASPECTS).15 The SWIFT-PRIME trial (Solitaire With the Intention for Thrombectomy as Primary Endovascular Treatment for Acute Ischemic Stroke) definitions were applied for puncture, symptomatic intracranial hemorrhage, and vessel segments.6

Technique Core Laboratory

An independent technique core laboratory (O.O.Z.), blinded to the clinical outcomes, reviewed all procedural reports and angiographic imaging data to abstract the stent retriever size used, the site-adjudicated target clot location, recanalization after each pass, and the number of stent retriever passes. The stent retriever sizes used were classified into 3 groups: (1) 4×20, (2) 4×40, and (3) 6×30.

Outcome Measures

Clinical Outcomes

The primary clinical efficacy outcome was the rate of functional independence (modified Rankin Scale, 0–2) at 90 days post-procedure. Safety evaluations included incidence of neurological deterioration events (defined as worsening of National Institutes of Health Stroke Scale by 4 points), symptomatic intracranial hemorrhage, device-related serious adverse events, and mortality ≤90 days post-procedure.

Angiographic and Procedural Outcomes

The primary angiographic outcome was the rate of first-pass effect (FPE) after the first stent retriever size used.16 FPE is defined as achieving near-complete revascularization (mTICI, ≥2c),17,18 following a single thrombectomy device pass and without the use of rescue therapy. Achieving modified FPE (mFPE) was also assessed between groups, which is defined as meeting all criteria for FPE but achieving mTICI ≥2b after the first pass.16 The impact of first stent retriever size on angiographic outcome was also assessed at different occlusion sites.

Secondary angiographic outcome measures included rates of distal embolization, embolization into new territory, and final mTICI. Puncture to reperfusion (defined as time from puncture to achieving mTICI ≥2b) or end of procedure were also compared between the groups.

Statistical Analysis

Continuous variables are presented using the mean, SD, and median with interquartile range, whereas categorical variables are presented with frequency distributions. For nominal comparisons, tests involving 2 independent subgroups were analyzed using a t test or Wilcoxon rank-sum test for continuous variables and Pearson χ2 or Fisher exact test for categorical variables. Comparisons of >2 subgroups were made using the ANOVA for continuous variables and Pearson χ2 test for categorical variables. Comparisons of clinical outcomes were made between subgroups (based on occlusion site) and adjusted for baseline and procedural characteristics (Tables I and II in the online-only Data Supplement). For analyses involving adjustment for baseline covariates, logistic regression was used for binary and ordinal outcomes, with contrasts between subgroups presented for pairwise comparisons among >2 subgroups. Results of logistic regressions are presented using odds ratios (ORs) with 2-sided 95% CIs.

All statistical tests were 2 sided, with P<0.05 considered statistically significant. Statistical analyses were conducted using SAS, version 9.3 (SAS Institute, Cary, NC), and R, version 3.2 (R Foundation for Statistical Computing, Vienna, Austria).

Results

Stent Retriever Length and Diameter Population

Baseline Features and Demographics

A total of 715 patients met the inclusion criteria for this analysis (Figure 1). The 4×20 stent retriever was used in 201 (28%) patients, 4×40 was used in 270 (38%) patients, and the 6×30 was used in 244 (34%) patients. Baseline characteristics were mostly similar between these groups (Table 1).

Table 1. Baseline Variables Among Different Stent Retriever Diameters and Lengths

Solitaire 4×20 (n=201)Solitaire 4×40 (n=270)Solitaire 6×30 (n=244)P Value
4×20 vs 4×404×20 vs 6×304×40 vs 6×30
Age, y69.1±15.01 (201); 71.0 (61–80)67.7±15.60 (270); 70.0 (60–79)69.6±14.54 (244); 72.0 (61.5–80)0.27140.89160.1937
Sex: men103 (51.2%)131 (48.5%)123 (50.4%)0.55850.86100.6685
 Atrial flutter or fibrillation91 (45.3%)120 (44.4%)103 (42.2%)0.85790.51700.6103
 Systemic hypertension153 (76.1%)191 (70.7%)184 (75.4%)0.19330.86210.2340
 Diabetes mellitus49 (24.4%)70 (25.9%)80 (32.8%)0.70220.05170.0875
 Coronary artery disease55 (27.4%)77 (28.5%)65 (26.6%)0.78240.86400.6342
 Hyperlipidemia91 (45.3%)104 (38.5%)118 (48.4%)0.14100.51610.0245
 Peripheral artery disease5 (2.5%)8 (3.0%)17 (7.0%)0.75540.03010.0351
 Carotid artery disease10 (5.0%)35 (13.0%)15 (6.1%)0.00350.59300.0092
 Current or prior tobacco use101 (50.2%)123 (45.6%)114 (46.7%)0.31310.45870.7912
Prestroke mRS score0.18420.63330.3261
 0158 (78.6%)194 (71.9%)183 (75.0%)
 137 (18.4%)69 (25.6%)51 (20.9%)
 2*6 (3.0%)7 (2.6%)10 (4.1%)
Initial qualifying NIHSS17.5±5.74 (201); 18.0 (13–22)17.2±5.44 (270); 17.0 (13–22)17.9±5.36 (244); 18.0 (14–21)0.58940.51030.1651
Baseline ASPECTS8.4±1.54 (165); 9.0 (8–9)8.2±1.62 (222); 8.0 (8–9)8.2±1.48 (190); 8.0 (8–9)0.09340.07660.8746
IV tPA delivered116 (57.7%)175 (64.8%)157 (64.3%)0.15020.19250.9113
IA tPA delivered19 (9.5%)12 (4.4%)14 (5.7%)0.03020.13660.5041
General anesthesia used61 (30.3%)57 (21.1%)62 (25.4%)0.02210.24640.2486
Adjunctive technique use<0.00010.0003<0.0001
 Balloon guide use109/201 (54.2%)205/270 (75.9%)91/244 (37.3%)
 Conventional guide20/201 (10.0%)13/270 (4.8%)17/244 (7.0%)
 Distal catheter55/201 (27.4%)45/270 (16.7%)123/244 (50.4%)
Vessel treated on first pass<0.0001<0.0001<0.0001
 ICA14 (7.0%)43 (15.9%)107 (43.9%)
 MCA-M1122 (60.7%)186 (68.9%)126 (51.6%)
 MCA-M265 (32.3%)41 (15.2%)11 (4.5%)
Stroke onset to puncture, min234.7±94.7 (197); 216.0 (159–297)226.5±97.3 (268); 208.0 (150–291)208.3±104.6 (244); 188.0 (128–278)0.31360.00150.0157

Data are n (%) or mean±SD (n); median (IQR). ASPECTS indicates Alberta Stroke Program Early CT Score; IA, intra-arterial; ICA, internal carotid artery; IQR, interquartile range; IV, intravenous; MCA, middle cerebral artery; mRS, modified Rankin Scale; NIHSS, National Institutes of Health Stroke Scale; SWIFT-PRIME, Solitaire With the Intention for Thrombectomy as Primary Endovascular Treatment for Acute Ischemic Stroke; and tPA, tissue-type plasminogen activator.

*The protocol was amended to restrict enrollment to mRS scores of 0–1 to ensure consistency with SWIFT-PRIME trial enrollment criteria.

Notably, there was a higher incidence of hyperlipidemia in the 6×30 group compared with the 4×40 group (P=0.024), and a higher incidence of carotid artery disease in the 4×40 group compared with both the 4×20 (P=0.0035) and 6×30 (P=0.009) groups. There was also a higher incidence of peripheral artery disease in the 4×20 and 4×40 groups compared with the 6×30 group (P=0.03 and P=0.035, respectively). In addition, more frequent use of balloon guide catheter, general anesthesia, and intra-arterial tPA was observed in the 4×20 group compared with the 4×40 group (P<0.0001, P=0.022, and P=0.03, respectively). Shorter time from stroke onset to puncture was observed in the 6×30 group compared with both the 4×20 (P=0.0015) and 4×40 (P=0.016) groups.

Angiographic and Clinical Outcomes

The 4×40 stent retriever group had the highest rate of revascularization to FPE (49% [131 of 269 patients]) compared with the 6×30 group (36% [86 of 242 patients]; P=0.003), as shown in Table 2 and Figure 2. Similarly, the 4×40 group had a higher rate of mFPE (69% [185 of 269 patients]) compared with the 4×20 group (60% [119 of 200 patients]; P=0.038) and the 6x30 group (52% [126 of 242 patients]; P=0.0001). Final revascularization was not significantly different across the 3 groups.

Table 2. Clinical and Angiographic Outcomes by Stent Retriever Diameters and Lengths

OutcomeSolitaire 4×20 (n=201)Solitaire 4×40 (n=270)Solitaire 6×30 (n=244)P Value
4×20 vs 4×404×20 vs 6×304×40 vs 6×30
Clinical outcomes
 mRS score 0–2 at 90 d104/185 (56.2%)142/255 (55.7%)118/220 (53.6%)0.91200.60330.6545
Safety outcomes
 All-cause mortality at 90 d25/185 (13.5%)51/255 (20.0%)33/220 (15.0%)0.05980.73470.1005
 Symptomatic ICH4/185 (2.2%)5/255 (2.0%)00.20220.03350.0364
Angiographic outcomes
 Primary outcome
  FPE (mTICI ≥2c after first pass)82/200 (41.0%)131/269 (48.7%)86/242 (35.5%)0.09770.23890.0027
  mFPE (mTICI ≥2b after first pass)119/200 (59.5%)185/269 (68.8%)126/242 (52.1%)0.03750.11760.0001
Final mTICI*0.26290.37490.8804
 325/166 (15.1%)23/225 (10.2%)26/202 (12.9%)
 2b119/166 (71.7%)181/225 (80.4%)157/202 (77.7%)
 2a14/166 (8.4%)16/225 (7.1%)16/202 (7.9%)
 12/166 (1.2%)2/225 (0.9%)1/202 (0.5%)
 06/166 (3.6%)3/225 (1.3%)2/202 (1.0%)
Final mTICI ≥2b*144/166 (86.7%)204/225 (90.7%)183/202 (90.6%)0.22080.24320.9795
No. of device passes1.8±1.07 (201); 1.0 (1–2)1.7±1.07 (270); 1.0 (1–2)2.1±1.50 (244); 2.0 (1–3)0.04800.07710.0001
Rescue device used9.5% (19/201)6.3% (17/270)16.0% (39/244)0.20220.04170.0004
>3 Solitaire passes5.0% (10/201)3.7% (10/270)5.7% (14/244)0.49850.72300.2751
Vessel cutoff in downstream territory*94/166 (56.6%)123/225 (54.7%)111/202 (55.0%)0.69990.74740.9531
Emboli to new territory*4/166 (2.4%)01/202 (0.5%)0.01930.11440.2907
Puncture to revascularization, min36.0 (25–57); 43.1±26.66 (187)33.0 (23–50); 40.5±25.16 (263)34.0 (24–56); 42.8±27.06 (238)0.25090.73610.4208

Data are n (%) or mean±SD (n); median (IQR). FPE indicates first-pass effect; ICH, intracranial hemorrhage; IQR, interquartile range; mFPE, modified first-pass effect; mRS, modified Rankin Scale; and mTICI, modified Thrombolysis in Cerebral Infarction.

*Assessed by image core laboratory.

Figure 2.

Figure 2. Rate of first-pass effect based on stent retriever size in the full internal carotid artery (ICA) occlusion cohorts. STRATIS indicates Systematic Evaluation of Patients Treated With Neurothrombectomy Devices for Acute Ischemic Stroke.

The 4×40 group had the lowest number of device passes with an average of 1.7±1.07 passes compared with 1.8±1.07 in the 4×20 group (P=0.048) and 2.1±1.5 in the 6×30 group (P=0.0001). The 6×30 group had the highest rate of rescue device used (16% [39 of 244 patients]) compared with both the 4×20 (10% [19 of 201 patients]; P=0.042) and 4×40 groups (6% [17 of 270 patients]; P=0.0004). The rate of embolization into new territory was significantly lower with the longer 4×40 stent retriever (0% [0 of 225 patients]) compared with the shorter 4×20 stent retriever (2% [4 of 166 patients]; P=0.019) but did not differ from the larger diameter 6×30 stent retriever (1% [1 of 202 patients]; P=0.29). There was no difference in the rate of distal embolization between the groups (Table 2).

Use of the longer stent retriever (4×40) as a first device was an independent predictor of achieving mFPE (adjusted OR, 1.55 [95% CI, 1.03–2.32]; P=0.037 for 4×40 versus 6×30), and (adjusted OR, 1.54 [95% CI, 1.03–2.32]; P=0.037 for 4×40 versus 4×20) after adjusting for the National Institutes of Health Stroke Scale, ASPECTS, occlusion location, use of intravenous tPA, use of intra-arterial tPA, female sex, octogenarian status, balloon guide catheter, or distal access catheter use, presence of atrial fibrillation, and onset to puncture time (Tables I and II in the online-only Data Supplement).

There were no significant differences in functional dependence at 90 days across the groups (Figure 3; Table 2). When comparing safety outcomes, there was a lower incidence of symptomatic intracranial hemorrhage in the 6×30 group (0% [0 of 220 patients]) compared with both the 4×20 group (2% [4 of 185 patients]; P=0.03) and the 4×40 group (2% [5 of 255 patients]; P=0.36), although the total incidence of symptomatic intracranial hemorrhage was small (n≤5) in all groups. There were no significant differences in all-cause mortality at 90 days post-procedure (Table 2). Baseline characteristics that predicted good clinical outcome are presented in Table II in the online-only Data Supplement) and included age (unit, 10 years; OR, 0.70 [95% CI, 0.61–0.81]; P<0.001), National Institutes of Health Stroke Scale (unit, 5 points; OR, 0.81 [95% CI, 0.68–0.96]; P=0.017), baseline ASPECTS (unit, 1 point; OR, 1.34 [95% CI, 1.17–1.53]; P<0.001), an M1 occlusion (versus internal carotid artery [ICA] OR, 1.66 [95% CI, 1.06–2.58]; P<0.026), and onset to arterial puncture (unit, 60 minutes; OR, 0.89 [95% CI, 0.80–0.99]; P<0.001).

Figure 3.

Figure 3. Distribution of modified Rankin Scale scores at 90 d according to stent retriever size.

We then evaluated the revascularization efficacy of stent retriever sizes at different clot locations to test the hypothesis that a larger stent would be more effective at the ICA occlusion versus middle cerebral artery (MCA) occlusion. In the MCA occlusion population, the majority of patients (n=186) were treated with the longer 4×40 stent retriever device (4×20, n=122 and 6×30, n=126), and this group had the highest rate of mFPE after first pass (72% [133 of 186 patients]; P=0.029 versus 4×20; Table III in the online-only Data Supplement). In patients with an ICA occlusion, the majority (n=107) were treated with the larger diameter 6×30 device (4×20, n=14 and 4×40, n=43); however, patients treated with the 4×40 stent retriever had the highest rate of mFPE after first pass (62% [26 of 42 patients]; P=0.006 versus 6×30; Table IV in the online-only Data Supplement). In patients with an M2 occlusion, the majority (n=65) were treated with the shorter 4×20 stent retriever (4×40, n=41 and 6×30, n=11), and there were no significant differences in the rates of FPE of mFPE revascularization (Figure 2; Table V in the online-only Data Supplement).

Discussion

We investigated the impact of stent retriever size on clinical and angiographic outcomes after mechanical thrombectomy for acute ischemic stroke using data from the STRATIS registry. We found that the longer stent retriever showed a higher rate of revascularization when compared with the shorter or larger diameter stent retriever but was not associated with better clinical outcome. These results are consistent with prior studies of the impact of stent retrievers on both clinical and angiographic outcomes from large retrospective and smaller cohort studies.19–21 However, this study is the first to demonstrate that a longer stent retriever is more likely to achieve FPE and mFPE on first pass, suggesting that routing use of longer stent retrievers may improve the rates of early revascularization success.

Stent Retriever Size and Outcomes

A surprising finding was that the length of the stent retriever had a greater impact on outcomes than diameter. The 4×40 stent retriever was associated with the highest rates of FPE and mFPE revascularization, although this did not correlate with better clinical outcomes, likely because ischemia-reperfusion injury may not be resolved with complete recanalization. Another potential explanation is that, in spite of the statistical difference in revascularization rates, the absolute gain was not high enough to translate to significant differences in clinical outcome. The TRACK registry (TREVO Stent-Retriever Acute Stroke) showed a strong correlation between first-pass revascularization and good clinical outcomes,22 although the rates are difficult to compare with this study because the TRACK registry used FPE=Thrombolysis in Cerebral Infarction 3 as its metric, not mTICI ≥2c. Given this, we recommend further study of stent retriever size and the correlation between FPE and clinical outcome.

Larger Versus Longer Stent Retriever

Patients with an MCA occlusion were divided into equal sample sizes across the 3 stent retriever sizes. We hypothesized that the larger and longer stent retrievers (eg, 6×30) would achieve the highest rate of first-pass revascularization, as a recent analysis of 420 thrombectomies found that the shorter stent retriever group had more frequent complications and that the longer retriever group had higher rates of first-pass reperfusion (62% versus 50%).10 We found that the longer (4×40) stent retriever showed higher rates of mFPE and a trend toward more successful FPE revascularization. The 6×30 did not perform better than 4×20 for MCA occlusions, despite its greater length and diameter. In fact, the 4×40 had the highest rate of revascularization in this location. This finding may be related to possible vasospasm and vessel irritation when a larger diameter stent is used in a small artery, such as the MCA. Based on this finding, it is possible that there is a limit to the benefit of diameter size above the target vessel diameter.

For ICA occlusions, the 6×30 stent retriever was the most frequently used device. However, there was no clear advantage of the 6×30 over the 4×40 size, and a trend toward better performance with early revascularization was found when using the 4×40 stent retriever. This suggests that clot retrieval efficiency does not improve above a certain diameter in a given target vessel diameter or location. One might hypothesize that a larger diameter may increase the risk of vascular injury with a minimal gain in revascularization rate because of reduced radial force gradient with a 4-mm stent across the different segments of the cerebrovascular tree than with a 6-mm device, which may expose the captured clot to higher radial force changes, given the wider discrepancy in device to vessel diameter. The increased efficiency of a longer stent retriever, on the contrary, could also be explained by the increased distal protection it provides to the clot and reduced likelihood of clot migration out of the stent if the stent retriever is longer. Future studies may shed light on the optimal diameter and length of stent retrievers for each clot location.

Limitations

These are observational findings from a prospective study with a prespecified study design, which did not randomize the allocation of stent retriever sizes, creating the potential for bias. Additional limitations include operator and center effects, in which an imbalance may exist in stent retriever size availability and preference. Operators’ prior experience, based on clot type or patient characteristics, may have affected their choice of first device size, creating selection bias.

Technique analysis was limited by its relation to site-reported clinical outcome, although the central technique laboratory was blinded to clinical outcome. Stent retriever sizes were evaluated and compared using FPE as the primary angiographic outcome measure. FPE seems to be an appropriate choice of primary revascularization outcome, given interventionalists’ tendencies to switch stent retriever or adjunctive device after 1 or 2 passes; however, the grading was not blinded to stent size, which may have created bias.

Additionally, clinical outcomes and final reperfusion can be impacted by the use of adjunctive techniques.10 The results of this study are based on a sample of patients that were treated with adjunctive techniques that included balloon guide catheters, distal access catheters, or conventional guide catheters. Thus, it is possible that the combination of adjunctive techniques with the stent retriever contribute to the clinical outcomes and early reperfusion rates observed in this study.

A final limitation was the lack of 6×40 stent in the STRATIS registry because this device was not commercially available at the time of the study. In its place, we compared the 4×40 to the 6×30, which limits the interpretation of diameter-based results. Nevertheless, 6×30 did not perform better than 4×20 in MCA occlusion, supporting our finding that longer 4-mm stents are the most promising in achieving revascularization success. Finally, technical advances are constantly occurring. Newer and enhanced stent retrievers have been introduced since the STRATIS study, including the 6×40 size; hence, outcomes may change accordingly.

Conclusions

In the STRATIS registry, the 4×40 stent retriever size was associated with higher rates of early revascularization for MCA occlusions, as measured by FPE and mFPE after a single device pass. For ICA occlusions, the 4×40 stent retriever also had a higher rate of mFPE over the 4×20 and 6×30 sizes. There was no difference in revascularization or mFPE rates for M2 occlusions, nor in clinical outcomes for any of the devices. These results suggest that routine use of the 4×40 stent retriever for MCA and ICA occlusions may improve early revascularization rates.

Acknowledgments

We acknowledge Medtronic for their editing assistance.

Footnotes

The online-only Data Supplement is available with this article at https://www.ahajournals.org/doi/suppl/10.1161/STROKEAHA.118.022987.

Correspondence to Osama O. Zaidat, MD, Mercy Health - St. Vincent Mercy Medical Center, 2222 Cherry St, M200, Toledo, OH 43608. Email

References

  • 1. Berkhemer OA, Fransen PS, Beumer D, van den Berg LA, Lingsma HF, Yoo AJ, et al; MR CLEAN Investigators. A randomized trial of intraarterial treatment for acute ischemic stroke.N Engl J Med. 2015; 372:11–20. doi: 10.1056/NEJMoa1411587CrossrefMedlineGoogle Scholar
  • 2. Campbell BC, Mitchell PJ, Kleinig TJ, Dewey HM, Churilov L, Yassi N, et al; EXTEND-IA Investigators. Endovascular therapy for ischemic stroke with perfusion-imaging selection.N Engl J Med. 2015; 372:1009–1018. doi: 10.1056/NEJMoa1414792CrossrefMedlineGoogle Scholar
  • 3. Goyal M, Demchuk AM, Menon BK, Eesa M, Rempel JL, Thornton J, et al; ESCAPE Trial Investigators. Randomized assessment of rapid endovascular treatment of ischemic stroke.N Engl J Med. 2015; 372:1019–1030. doi: 10.1056/NEJMoa1414905CrossrefMedlineGoogle Scholar
  • 4. Bracard S, Ducrocq X, Mas JL, Soudant M, Oppenheim C, Moulin T, et al; THRACE Investigators. Mechanical thrombectomy after intravenous alteplase versus alteplase alone after stroke (THRACE): a randomised controlled trial.Lancet Neurol. 2016; 15:1138–1147. doi: 10.1016/S1474-4422(16)30177-6CrossrefMedlineGoogle Scholar
  • 5. Jovin TG, Chamorro A, Cobo E, de Miquel MA, Molina CA, Rovira A, et al; REVASCAT Trial Investigators. Thrombectomy within 8 hours after symptom onset in ischemic stroke.N Engl J Med. 2015; 372:2296–2306. doi: 10.1056/NEJMoa1503780CrossrefMedlineGoogle Scholar
  • 6. Saver JL, Goyal M, Bonafe A, Diener HC, Levy EI, Pereira VM, et al; SWIFT PRIME Investigators. Stent-retriever thrombectomy after intravenous t-PA vs. t-PA alone in stroke.N Engl J Med. 2015; 372:2285–2295. doi: 10.1056/NEJMoa1415061CrossrefMedlineGoogle Scholar
  • 7. Powers WJ, Derdeyn CP, Biller J, Coffey CS, Hoh BL, Jauch EC, et al; American Heart Association Stroke Council. 2015 American Heart Association/American Stroke Association focused update of the 2013 guidelines for the early management of patients with acute ischemic stroke regarding endovascular treatment: a guideline for healthcare professionals from the American Heart Association/American Stroke Association.Stroke. 2015; 46:3020–3035. doi: 10.1161/STR.0000000000000074LinkGoogle Scholar
  • 8. Bhatia R, Hill MD, Shobha N, Menon B, Bal S, Kochar P, et al. Low rates of acute recanalization with intravenous recombinant tissue plasminogen activator in ischemic stroke: real-world experience and a call for action.Stroke. 2010; 41:2254–2258. doi: 10.1161/STROKEAHA.110.592535LinkGoogle Scholar
  • 9. Kitahara H, Okada K, Kimura T, Yock PG, Lansky AJ, Popma JJ, et al. Impact of stent size selection on acute and long-term outcomes after drug-eluting stent implantation in de novo coronary lesions.Circ Cardiovasc Interv. 2017; 10:e004795LinkGoogle Scholar
  • 10. Haussen DC, Al-Bayati AR, Grossberg JA, Bouslama M, Barreira C, Bianchi N, et al. Longer stent retrievers enhance thrombectomy performance in acute stroke.J Neurointerv Surg. 2019; 11:6–8. doi: 10.1136/neurintsurg-2018-013918CrossrefMedlineGoogle Scholar
  • 11. Yang D, Hao Y, Zi W, Wang H, Zheng D, Li H, et al. Effect of retrievable stent size on endovascular treatment of acute ischemic stroke: a multicenter study.AJNR Am J Neuroradiol. 2017; 38:1586–1593. doi: 10.3174/ajnr.A5232CrossrefMedlineGoogle Scholar
  • 12. Jahan R. Solitaire flow-restoration device for treatment of acute ischemic stroke: safety and recanalization efficacy study in a swine vessel occlusion model.AJNR Am J Neuroradiol. 2010; 31:1938–1943. doi: 10.3174/ajnr.A2169CrossrefMedlineGoogle Scholar
  • 13. Machi P, Jourdan F, Ambard D, Reynaud C, Lobotesis K, Sanchez M, et al. Experimental evaluation of stent retrievers’ mechanical properties and effectiveness.J Neurointerv Surg. 2017; 9:257–263. doi: 10.1136/neurintsurg-2015-012213CrossrefMedlineGoogle Scholar
  • 14. Mueller-Kronast NH, Zaidat OO, Froehler MT, Jahan R, Aziz-Sultan MA, Klucznik RP, et al; STRATIS Investigators. Systematic evaluation of patients treated with neurothrombectomy devices for acute ischemic stroke: primary results of the STRATIS registry.Stroke. 2017; 48:2760–2768. doi: 10.1161/STROKEAHA.117.016456LinkGoogle Scholar
  • 15. Barber PA, Demchuk AM, Zhang J, Buchan AM. Validity and reliability of a quantitative computed tomography score in predicting outcome of hyperacute stroke before thrombolytic therapy. ASPECTS Study Group. Alberta Stroke Programme Early CT Score.Lancet. 2000; 355:1670–1674.CrossrefMedlineGoogle Scholar
  • 16. Zaidat OO, Castonguay AC, Linfante I, Gupta R, Martin CO, Holloway WE, et al. First pass effect: a new measure for stroke thrombectomy devices.Stroke. 2018; 49:660–666. doi: 10.1161/STROKEAHA.117.020315LinkGoogle Scholar
  • 17. Almekhlafi MA, Mishra S, Desai JA, Nambiar V, Volny O, Goel A, et al. Not all “successful” angiographic reperfusion patients are an equal validation of a modified TICI scoring system.Interv Neuroradiol. 2014; 20:21–27. doi: 10.15274/INR-2014-10004CrossrefMedlineGoogle Scholar
  • 18. Goyal M, Fargen KM, Turk AS, Mocco J, Liebeskind DS, Frei D, et al. 2C or not 2C: defining an improved revascularization grading scale and the need for standardization of angiography outcomes in stroke trials.J Neurointerv Surg. 2014; 6:83–86. doi: 10.1136/neurintsurg-2013-010665CrossrefMedlineGoogle Scholar
  • 19. Nguyen TN, Malisch T, Castonguay AC, Gupta R, Sun CH, Martin CO, et al. Balloon guide catheter improves revascularization and clinical outcomes with the Solitaire device: analysis of the North American Solitaire Acute Stroke Registry.Stroke. 2014; 45:141–145. doi: 10.1161/STROKEAHA.113.002407LinkGoogle Scholar
  • 20. Velasco A, Buerke B, Stracke CP, Berkemeyer S, Mosimann PJ, Schwindt W, et al. Comparison of a balloon guide catheter and a non-balloon guide catheter for mechanical thrombectomy.Radiology. 2016; 280:169–176. doi: 10.1148/radiol.2015150575CrossrefMedlineGoogle Scholar
  • 21. Pereira V, Siddiqui A, Jovin T, Yavagal D, Levy E, Bonafé A, et al. P-016 role of balloon guiding catheter in mechanical thrombectomy using stentretrivers subgroup analysis of SWIFT PRIME: Abstract P-016 Table 1. J Neurointerv Surg. 2015; 7:A30.CrossrefGoogle Scholar
  • 22. Zaidat OO, Castonguay AC, Nogueira RG, Haussen DC, English JD, Satti SR, et al. TREVO stent-retriever mechanical thrombectomy for acute ischemic stroke secondary to large vessel occlusion registry.J Neurointerv Surg. 2018; 10:516–524. doi: 10.1136/neurintsurg-2017-013328CrossrefMedlineGoogle Scholar

eLetters(0)

eLetters should relate to an article recently published in the journal and are not a forum for providing unpublished data. Comments are reviewed for appropriate use of tone and language. Comments are not peer-reviewed. Acceptable comments are posted to the journal website only. Comments are not published in an issue and are not indexed in PubMed. Comments should be no longer than 500 words and will only be posted online. References are limited to 10. Authors of the article cited in the comment will be invited to reply, as appropriate.

Comments and feedback on AHA/ASA Scientific Statements and Guidelines should be directed to the AHA/ASA Manuscript Oversight Committee via its Correspondence page.