Abstract
Introduction
Endovascular mechanical thrombectomy (MT) is an established treatment for large vessel occlusion strokes with a National Institutes of Health Stroke Scale (NIHSS) score of 6 or higher. Data pertaining to minor strokes, medium, or distal vessel occlusions, and most effective MT technique is limited and controversial.
Methods
A multicenter retrospective study of all patients treated with MT presenting with NIHSS score of 5 or less at 29 comprehensive stroke centers. The cohort was dichotomized based on location of occlusion (proximal vs. distal) and divided based on MT technique (direct aspiration first-pass technique [ADAPT], stent retriever [SR], and primary combined [PC]). Outcomes at discharge and 90 days were compared between proximal and distal occlusion groups, and across MT techniques.
Results
The cohort included 759 patients, 34% presented with distal occlusion. Distal occlusions were more likely to present with atrial fibrillation (p = 0.008) and receive IV tPA (p = 0.001). Clinical outcomes at discharge and 90 days were comparable between proximal and distal groups. Compared to SR, patients managed with ADAPT were more likely to have a modified Rankin Scale of 0–2 at discharge and at 90 days (p = 0.024 and p = 0.013). Primary combined compared to ADAPT, prior stroke, multiple passes, older age, and longer procedure time were independently associated with worse clinical outcome, while successful recanalization was positively associated with good clinical outcomes.
Conclusions
Proximal and distal occlusions with low NIHSS have comparable outcomes and safety profiles. While all MT techniques have a similar safety profile, ADAPT was associated with better clinical outcomes at discharge and 90 days.
Keywords: Thrombectomy, MVO, minor stroke
Introduction
Endovascular mechanical thrombectomy (MT) is the standard of care for patients with large vessel occlusion (LVO) and National Institutes of Health Stroke Scale (NIHSS) 6 or higher presenting within an appropriate time frame.1–5 There is retrospective data investigating the use of MT in patients with “minor” stroke (i.e., NIHSS < 6) which shows mixed results when comparing it to best medical management or intravenous thrombolytics (IVT).6–9 However, a recent systematic review suggests that there may be a benefit, 10 and a recent investigation suggests that it is more cost-effective than medical management with M1 occlusions. 11
We recently published a large multicenter registry experience demonstrating safety and efficacy of MT for patients with minor stroke compared to those with NIHSS greater than 6. 12 However, few (if any) reports have systematically analyzed the specific factors associated with good outcome for patients in this minor stroke category undergoing MT. Furthermore, while there are retrospective reports of efficacy in utilizing MT in patients with distal occlusions as well as ongoing clinical trials, 13 there are variable definitions of what constitutes “distal” and no comparisons of a proximal clot location. Finally, there are mixed reports in the literature for various MT techniques affecting clinical outcomes,14–18 but no analyses geared specifically at techniques in low NIHSS MT for LVO.
Here, we investigated the role that (1) location of occlusion and (2) technique employed during MT had on clinical outcomes for patients with minor stroke undergoing MT.
Methods
The Stroke Thrombectomy and Aneurysm Registry (STAR) is a large, international, prospectively maintained database with data from—at the time of the creation of this manuscript—29 centers. Each participating center obtained independent institutional review board approval for data sharing; subsequent data pooling and analysis were performed at the core institution. We analyzed all patients who underwent MT and presented with an NIHSS of 5 or less. Each center independently collected patient demographics, medical history, comorbidities, baseline modified Rankin Scale (mRS), details of presentation (including the NIHSS), details of the MT procedure (including location and technique), clinical outcomes, and complications.
For the first part of the analysis, patients were dichotomized into those with “proximal” occlusion locations which were conventional large vessels included in the major MT trials (internal carotid artery [ICA] and M1) as well as other large, proximal, posterior circulation vessels (vertebral artery and basilar artery), and those with “distal” occlusions, such as medium vessel occlusion or other sites not included in the major MT trials (A1/A2, M2, M3/4, and P1/2). The primary outcomes were functional independence (mRS 0–2) at 90 days and discharge. Secondary outcomes were hemorrhage, post procedural complications, and favorable change in NIHSS at discharge. For the second part of the analysis, we stratified patients by frontline technique used during the MT, which included aspiration (ADAPT), stent retriever (SR), and primary combined (PC; SOLUMBRA technique with both an aspiration catheter and a SR). We analyzed the same outcomes. We used the STROBE checklist and guidelines for compiling a cohort study.
Statistical analysis
All statistical analyses were performed using IBM SPSS Statistics v27 or GraphPad Prism v9. Patients were stratified across location of LVOs (proximal vs distal) or primary technique used for endovascular thrombectomy (ADAPT, SR, or Combined). For univariate analysis across these groups, parametric variables were compared using Student's t-test/One-way ANOVA; nonparametric variables were compared using Mann–Whitney/Kruskal–Wallis tests; and categorical variables were compared using Fischer/Chi-square tests. Tests were two-sided and α < 0.05 was considered significant. Multiple imputation was used to account for missing variables of the following baseline variables in the unmatched samples: sex (0.13%), race (15.7%), diabetes (1.01%), hypertension (1.01%), atrial fibrillation (1.01%), hyperlipidemia (1.01%), prior stroke (12.9%), baseline mRS (16.8%), and onset-to-puncture time (16.83%). Primary outcome (mRS at 90 days) and LVO location were used as predictors in the imputation model. The unadjusted odds ratio (OR) of favorable primary and secondary outcomes was calculated using independent logistic regression with LVO location or primary technique used as sole predictors. Multivariate mixed models were used to determine independent predictors of favorable mRS at 90 days or favorable change in NIHSS (defined as a decrease in presenting NIHSS). Variables were included in the models based on their statistical significance on univariate analysis (p < 0.1) or clinical significance.
Results
At the time of this investigation, the STAR registry contained data from 8972 MT procedures. There were 759 patients with low NIHSS (less than 6) and that were included in the analysis.
Table 1 shows the demographics and characteristics of the cohort after stratifying patients based on location of occlusion. Patients in the distal group were more likely to be female (54.1% vs. 45.2%, p = 0.022), African American (13.7% vs. 8.6%, p < 0.001), or Hispanic (8.8% vs. 4.1%, p < 0.001), and have atrial fibrillation (34% vs. 24.6%, p = 0.008) as compared to the proximal group. Also, NIHSS was slightly higher at presentation (3.6 ± 1.4 vs. 3.1 ± 1.6, p < 0.001) and onset-to-groin time was shorter (447 ± 394 vs. 611 ± 921 min, p = 0.002). Technical details are provided at the bottom of the table; patients in the distal group were more likely to receive IV tPA (41.3% vs. 29.5%, p = 0.001), undergo ADAPT (39.4% vs. 30.7%, p = 0.022), less likely to require angioplasty of the ICA (3.8% vs. 23.2%, p < 0.001), and had higher final TICI scores of 3 (41.3% vs 29.5%, p = 0.019) as compared to the proximal group.
Table 1.
Demographics, characteristics, and procedural details for proximal and distal vessel occlusions.
| Variable | Location of occlusion | P value | |||
|---|---|---|---|---|---|
| Proximal (ICA/M1;vert/basilar) |
Distal (all other) |
||||
| N | Mean (SD) N (%) Median (IQR) |
N | Mean (SD) N (%) Median [IQR] |
||
| Baseline characteristics | |||||
| Agea | 502 | 66.1 (14.6) | 257 | 68.2 (14.6) | 0.118 |
| Femaleb | 502 | 227 (45.2%) | 257 | 139 (54.1%) | 0.022 |
| Raceb | 439 | 204 | <0.001 | ||
| White | 247 (56.3%) | 120 (58.8%) | |||
| African American | 38 (8.6%) | 28 (13.7%) | |||
| Hispanic | 18 (4.1%) | 18 (8.8%) | |||
| Other | 136 (31%) | 38 (18.7%) | |||
| Comorbiditiesb | |||||
| Diabetes | 500 | 151 (30.2%) | 254 | 76 (29.9%) | 1 |
| Hypertension | 500 | 334 (66.8%) | 254 | 177 (69.7%) | 0.458 |
| Atrial fibrillation | 499 | 123 (24.6%) | 253 | 86 (34%) | 0.008 |
| Hyperlipidemia | 500 | 221 (44.2%) | 254 | 97 (38.2%) | 0.119 |
| CHF | 209 | 22 (10.5%) | 150 | 19 (12.7%) | 0.614 |
| Prior strokeb | 443 | 65 (14.7%) | 219 | 34 (15.5%) | 0.817 |
| Smoking statusb | 287 | 169 | 0.788 | ||
| Never smoker | 201 (70%) | 116 (68.6%) | |||
| Previous smoker | 36 (12.5%) | 25 (14.8%) | |||
| Current smoker | 50 (17.4%) | 28 (16.6%) | |||
| Prestroke mRSc | 424 | 0 [0] | 209 | 0 [0] | 0.569 |
| Prestroke mRS <2b | 424 | 407 (96%) | 209 | 197 (94.3%) | 0.32 |
| Admission NIHSSa | 502 | 3.1 (1.6) | 257 | 3.6 (1.4) | <0.001 |
| Onset to groina | 416 | 611 (921) | 220 | 447 (394) | 0.002 |
| Posterior circulationb | 420 | 95 (22.6%) | 246 | 34 (13.8%) | 0.015 |
| Procedural variables | |||||
| IV-tPA useb | 495 | 146 (29.5%) | 252 | 104 (41.3%) | 0.001 |
| Techniqueb | 433 | 236 | 0.022 | ||
| ADAPT | 133 (30.7%) | 93 (39.4%) | |||
| Stent retriever | 128 (29.6%) | 52 (22%) | |||
| Primary combined | 146 (33.7%) | 84 (35.6%) | |||
| Other | 26 (6%) | 7 (3%) | |||
| ICA angioplastyb | 302 | 70 (23.2%) | 157 | 6 (3.8%) | <0.001 |
| IA-tPA useb | 410 | 32 (7.8%) | 242 | 24 (9.9%) | 0.386 |
| Attemptsc | 341 | 2 [2] | 217 | 2 [2] | 0.433 |
| Time to recanalizationa | 459 | 54 (43) | 223 | 51 (39) | 0.376 |
| Total procedure timea | 166 | 63 (48) | 124 | 58 (47) | 0.594 |
| Final mTICI scoreb | 495 | 252 | 0.019 | ||
| 0 | 26 (5.5%) | 13 (5.3%) | |||
| 1 | 10 (2.1%) | 8 (3.2%) | |||
| 2A | 24 (5.1%) | 30 (12.1%) | |||
| 2B | 146 (30.9%) | 75 (30.4%) | |||
| 2C | 40 (8.5%) | 20 (8.1%) | |||
| 3 | 146 (29.5%) | 104 (41.3%) | |||
| Complicationsb | 341 | 28 (8.2%) | 212 | 17 (8%) | 1 |
NIHSS: National Institutes of Health Stroke Scale; IV-tPA: intravenous tissue plasminogen activator; ICA: internal carotid artery; ADAPT: A direct aspiration first pass technique; Primary Combined: ADAPT and stent retriever; mTICI: modified thrombolysis in cerebral infarction score; mRS: modified Rankin Scale.
ANOVA.
Chi Square.
Kruskal–Wallis.
p<0.05 values indicated in bold.
The clinical outcomes for both groups are listed in Table 2. Outcomes at 90 days and discharge were mostly comparable (Figure 1), though patients in the distal group were more likely to experience a favorable shift in NIHSS (i.e., reduction in presenting NIHSS) by discharge (60.5 vs. 49.8%, p = 0.027). Both the rates of intracranial hemorrhage and overall complication were similar between the groups as well.
Table 2.
Clinical outcomes based on location of occlusion.
| Outcomes | Proximal (ICA/M1;vert/basilar) |
Distal (all other) |
Unadjusted OR | P value | ||
|---|---|---|---|---|---|---|
| N | Mean (SD) N (%) Median [IQR] |
N | Mean (SD) N (%) Median (IQR) |
|||
| Outcome at 90 days | ||||||
| 90 days mRS 0–2 | 448 | 288 (64.3%) | 226 | 146 (64.6%) | 1.01 (0.73–1.42) | 0.936 |
| 90 days mRS 0–1 | 448 | 206 (46%) | 226 | 116 (51.3%) | 1.24 (0.9–1.71) | 0.19 |
| 90 days mortality | 448 | 42 (9.4%) | 226 | 20 (8.8%) | 0.94 (0.54–1.64) | 0.824 |
| Outcome at Discharge | ||||||
| Discharge mRS 0–2 | 379 | 224 (59.1%) | 207 | 121 (58.5%) | 0.97 (0.69–1.37) | 0.88 |
| Discharge mRS 0–1 | 379 | 152 (40.1%) | 207 | 95 (45.9%) | 1.27 (0.9–1.78) | 0.18 |
| Discharge Mortality | 379 | 20 (5.3%) | 207 | 13 (6.3%) | 1.25 (0.6–2.61) | 0.55 |
| Favorable Shift in NIHSS | 295 | 147 (49.8%) | 172 | 104 (60.5%) | 1.54 (1.05–2.26) | 0.027 |
| Hemorrhages | ||||||
| sICH/PH2 | 485 | 25 (5.2%) | 248 | 17 (6.9%) | 1.35 (0.72–2.56) | 0.35 |
| Any ICH | 475 | 89 (18.7%) | 246 | 48 (19.5%) | 1.05 (0.71–1.55) | 0.8 |
| Complications | 341 | 28 (8.2%) | 212 | 17 (8%) | 0.98 (0.52–1.83) | 0.94 |
ICA: internal carotid artery; SD: standard deviation; IQR: interquartile range; OR: odds ratio; mRS: modified Rankin scale; NIHSS: National Institutes of Health Stroke Scale; sICH: symptomatic intracranial hemorrhage; mRS: modified Rankin Scale.
p<0.05 values indicated in bold.
Figure 1.
Clinical outcomes at 90 days according to location of occlusion.
In Table 3, all patients undergoing MT are combined regardless of location of occlusion and stratified by the three main techniques employed. The percentage of patients managed with each technique in each vessel is shown in Figure 2. Clinical outcomes are displayed. Patients undergoing MT using ADAPT were more likely to have a good clinical outcome (i.e., mRS 0–2) at 90 days as compared to either SR or PC, regardless of anterior or posterior circulation status (Figure 3). Discharge mRS was also improved in the ADAPT group compared to SR. All three techniques had comparable rates of ICH and overall complications. When dichotomized into proximal and distal occlusions, a statistically significant improvement in outcomes was detected in the proximal cohort (Supplemental Table 1). Table 4 displays multivariate modeling for variables related to clinical outcomes, on the top for a good clinical outcome at 90 days (mRS 0–2) and on the bottom for a favorable change in NIHSS (from discharge to admission). For the primary outcome (i.e., mRS at 90 days), PC compared to ADAPT (OR = 0.5, p = 0.026), prior stroke (OR = 0.36, p = 0.008), multiple passes (OR = 0.77, p = 0.006), older age (OR = 0.96, p < 0.001), and longer procedure time (OR = 0.99, p = 0.031) were independently associated with worse clinical outcome, while successful recanalization was positively associated (OR = 4.67, p < 0.001) with good clinical outcomes. For favorable change in NIHSS, PC compared to ADAPT (OR = 0.5, p = 0.026) and longer procedure times (OR = 0.99, p = 0.003) also independent predictors of an unfavorable increase in NIHSS between admission and discharge, whereas successful recanalization (OR = 3.25, p = 0.002) and distal location of occlusion (OR = 2.03, p = 0.006) were found to be associated with a favorable decrease change in this measure.
Table 3.
Clinical outcomes based on technique employed for mechanical thrombectomy (MT).
| Outcomes | Frontline technique used | N | Mean (SD) N (%) Median [IQR] |
Unadjusted OR (95% CI) or unadjusted RR (95% CI) | P value |
|---|---|---|---|---|---|
| Outcome at 90 days | |||||
| 90 days mRS 0–2 * | ADAPT | 206 | 146 (70.9%) | Reference Category | |
| SR | 174 | 102 (58.6%) | 0.58 (0.38–0.89) | 0.013 | |
| Combined | 192 | 118 (61.5%) | 0.66 (0.43–0.99) | 0.048 | |
| 90 days mRS 0–1 * | ADAPT | 206 | 112 (54.4%) | Reference Category | |
| SR | 174 | 80 (46%) | 0.71 (0.48–1.07) | 0.103 | |
| Combined | 192 | 88 (45.8%) | 0.71 (0.48–1.05) | 0.089 | |
| 90 days mortality * | ADAPT | 206 | 17 (8.3%) | Reference Category | |
| SR | 174 | 14 (8%) | 0.97 (0.47–2.03) | 0.942 | |
| Combined | 192 | 21 (10.9%) | 1.37 (0.7–2.67) | 0.364 | |
| Outcome at discharge | |||||
| Discharge mRS 0–2 | ADAPT | 206 | 130 (63.1%) | Reference Category | |
| SR | 147 | 75 (51.0%) | 0.61 (0.4–0.94) | 0.024 | |
| Combined | 178 | 105 (56.1%) | 0.75 (0.5–1.12) | 0.16 | |
| Discharge mRS 0–1 | ADAPT | 206 | 97 (47.1%) | Reference Category | |
| SR | 147 | 51 (34.7%) | 0.6 (0.39–0.92) | 0.02 | |
| Combined | 178 | 75 (40.1%) | 0.75 (0.5–1.12) | 0.164 | |
| Discharge mortality | ADAPT | 206 | 15 (7.3%) | Reference Category | |
| SR | 147 | 6 (4.1%) | 0.54 (0.21–1.43) | 0.216 | |
| Combined | 178 | 11 (5.9%) | 0.8 (0.36–1.78) | 0.578 | |
| Favorable decrease in NIHSS (categorical) | ADAPT | 184 | 108 (58.7%) | Reference Category | |
| SR | 60 | 34 (56.7%) | 0.92 (0.51–1.66) | 0.782 | |
| Combined | 157 | 78 (49.7%) | 0.70 (0.45–1.07) | 0.096 | |
| Hemorrhages | |||||
| Any ICH | ADAPT | 221 | 48 (21.7%) | Reference Category | |
| SR | 169 | 38 (22.5%) | 1.05 (0.65–1.69) | 0.857 | |
| Combined | 232 | 30 (12.9%) | 0.54 (0.32–0.88) | 0.014 | |
| PH2/sICH | ADAPT | 223 | 14 (6.3%) | Reference Category | |
| SR | 170 | 8 (4.7%) | 0.74 (0.3–1.8) | 0.503 | |
| Combined | 234 | 10 (4.3%) | 0.67 (0.29–1.53) | 0.34 | |
| Complications | ADAPT | 209 | 19 (9.1%) | Reference Category | |
| SR | 105 | 12 (11.4%) | 1.29 (0.6–2.77) | 0.513 | |
| Combined | 201 | 14 (7.0%) | 0.75 (0.36–1.54) | 0.43 | |
SD: standard deviation; IQR: interquartile range; OR: odds ratio; CI: confidence interval; mRS: modified Rankin scale; NIHSS: National Institutes of Health Stroke Scale; sICH: symptomatic intracranial hemorrhage; ADAPT: A direct aspiration first pass technique; SR: stent retriever; Primary Combined: ADAPT and stent retriever; mRS: modified Rankin Scale.
p<0.05 values indicated in bold.
Figure 2.
Distribution of patients according to location of occlusion and mechanical thrombectomy (MT) technique utilized.
Figure 3.
Clinical outcomes at 90 days according to mechanical thrombectomy (MT) technique.
Table 4.
Multivariate models for good clinical outcome (i.e., mRS 0–2, top) and favorable change in National Institutes of Health Stroke Scale (NIHSS) (bottom).
| Predictors of good outcome (mRS 0–2) | ||
|---|---|---|
| Variable | aOR (95% CI) | P value |
| Age | 0.96 (0.94–0.98) | <0.001 |
| Race (white/nonwhite) | 1.52 (0.86–2.7) | 0.152 |
| Diabetes | 0.69 (0.4–1.18) | 0.175 |
| Hypertension | 0.74 (0.38–1.41) | 0.354 |
| Prior stroke | 0.36 (0.17–0.76) | 0.008 |
| Baseline mRS | 0.74 (0.52–1.05) | 0.095 |
| Posterior circulation | 0.89 (0.48–1.66) | 0.719 |
| IV-tPA | 1.3 (0.74–2.28) | 0.357 |
| Onset to puncture (mins) | 1 (1–1) | 0.583 |
| Number of passes | 0.77 (0.64–0.93) | 0.006 |
| Procedure time | 0.99 (0.99–1) | 0.031 |
| Successful recanalization | 4.67 (2.33–9.38) | <0.001 |
| Vessel (Distal vs Proximal) | 1.3 (0.77–2.19) | 0.334 |
| Technique | ||
| ADAPT | Reference Category | |
| SR vs ADAPT | 0.59 (0.29–1.23) | 0.158 |
| PC vs ADAPT | 0.5 (0.27–0.92) | 0.026 |
| Predictors of favorable NIHSS change | ||
| Variable | aOR (95% CI) | P value |
| Age | 0.98 (0.97–1) | 0.089 |
| Race (white/nonwhite) | 1.44 (0.8–2.6) | 0.221 |
| Diabetes | 0.95 (0.55–1.64) | 0.865 |
| Hypertension | 1.18 (0.65–2.16) | 0.582 |
| Prior stroke | 1.05 (0.48–2.29) | 0.901 |
| Baseline mRS | 0.93 (0.65–1.32) | 0.668 |
| Posterior circulation | 0.93 (0.52–1.7) | 0.825 |
| IV-tPA | 1.66 (0.97–2.83) | 0.064 |
| Onset to puncture (mins) | 1 (1–1) | 0.202 |
| Number of passes | 0.99 (0.83–1.19) | 0.943 |
| Procedure time | 0.99 (0.98–1) | 0.003 |
| Successful recanalization | 3.25 (1.56–6.76) | 0.002 |
| Vessel (Distal vs Proximal) | 2.03 (1.22–3.38) | 0.006 |
| Technique | ||
| ADAPT | Reference Category | |
| SR vs ADAPT | 0.59 (0.29–1.23) | 0.158 |
| PC vs ADAPT | 0.5 (0.27–0.92) | 0.026 |
aOR: adjusted odds ratio; CI: confidence interval; IV: intravenous; ADAPT: A direct aspiration first pass technique; SR: stent retriever; PC: primary combined: ADAPT and stent retriever; NIHSS: National Institutes of Health Stroke Scale; mRS: modified Rankin Scale.
p<0.05 values indicated in bold.
Discussion
We present a large cohort of patients undergoing MT with a low NIHSS (i.e., less than 6) and intracranial vessel occlusion (proximal and distal) in an effort to shed light on the important parameters affecting presentation and outcome. We found that (1) patients with proximal and distal clot locations had comparable outcomes, (2) ADAPT resulted in superior clinical outcomes in comparison to SR or PC, and (3) that there are specific factors associated with good and poor clinical outcomes for patients with LVO and low NIHSS treated with MT regardless of clot location.
Location of occlusion
Patients presenting with low NIHSS and a distal occlusion represent a distinctly different entity than those patients presenting with proximal occlusions. Patients with distal occlusion were more likely to harbor underlying atrial fibrillation and an absence of ICA angioplasty (and thus presumable associated tandem intracranial atherosclerotic disease [ICAD]), which may reflect the difference in etiopathogenesis of these occlusions. Furthermore, patients with distal occlusion had a higher NIHSS at the time of thrombectomy, which again may reflect the phenomenon that patients with proximal occlusion harbor ICAD more frequently and thus chronically developed collateral networks of cerebral perfusion, making the LVO better tolerated.19,20 This is reflected in the relatively high rate of ICA angioplasty in this proximal group (23.2%). Alternatively, the difference in baseline NIHSS may reflect stricter selection criteria for distal occlusion patients undergoing MT; this is further supported by the higher percentage of distal occlusion patients receiving IV tPA prior to thrombectomy, which is a more accepted first-line treatment for this patient subgroup despite its limited efficacy.21–24 Interestingly, patients with distal occlusions also experienced a favorable shift in NIHSS more often than the proximal group, perhaps due to a lack of underlying ICAD or due to a higher initial NIHSS score; however, there was no difference in 90-day outcomes between the two groups. This data emphasizes previous publications by our group as well as data from other studies regarding the efficacy and outcomes of distal vessel MT.25–29 Interestingly, we found a difference in ethnic distribution of patients with a higher African American and Hispanic population in the distal occlusion cohort. This is consistent with previous literature that shows these differences are not attributed to specific patient risk factors or comorbidities.30,31 An important limiting factor for MT in distal vessel occlusion is the theoretical concern for a high risk of complications due to manipulation of smaller more tortuous vessels. However, with the introduction of newer technology (such as smaller SRs and aspiration catheters designed for smaller vessels) as well as appropriate patient selection, this no longer seems to be an issue with both patient cohorts experiencing a similar post-intervention complication rate comparable to low rates reported in the literature.25,26 Ultimately, we did not find any difference in 90-day outcomes between the proximal and distal groups; however, generalized recommendations based on these data are limited due to the absence of a control group to compare outcomes of distal occlusion in the absence of MT. This highlights the need for prospective investigation into the precise role that MT plays in patients with distal occlusion. There are currently multiple randomized clinical trials underway specifically dedicated to understanding the role of MT in distal occlusions, including DISTAL (NCT05029414), DISTALS (NCT05152524), DISCOUNT (NCT05030142), and ESCAPE-MeVO (NCT05151172). 13
Mechanical thrombectomy technique
Most patients in STAR registry were treated via ADAPT, PC, or SR. There are some existing data supporting the use of ADAPT over PC in LVO due to better clinical outcomes14,15 or reduced procedural time. 16 There are also data from prospective randomized controlled trials showing equipoise between ADAPT and SR. 17 Finally, a recent summary of seven meta-analyses suggested that ADAPT was slightly more effective than SR in achieving reperfusion, but that there was insufficient evidence to totally clarify the superiority. 32
Data comparing the use of ADAPT vs SR in distal vessel occlusion is limited to a few studies and a subgroup analysis for M2 occlusions from the ASTER trial.18,33–35 There is some concern regarding the use of MT techniques in smaller thin-walled vessels of the distal intracranial circulation, which are theoretically more susceptible to perforation or dissection, especially with the SR. Furthermore, with more widespread use of MT, comparing the safety and efficacy profiles of the more cost-effective technique, ADAPT, to others becomes of utmost importance with some prior data showing a better safety profile for ADAPT in comparison to other techniques.15,33,36 In this study, similar to some of the previous data, the overall safety profile of all techniques used was similar with no significant difference in overall complication rate, especially regarding distal embolization and sICH.33–35 More importantly, complication rates were similar to those reported in MT for LVO, which reflects the improvement in technology in comparison to older devices.14,16,37 Discharge outcomes were slightly better for ADAPT in comparison to SR with a higher rate of good mRS at discharge; however, similar rates of favorable shift in NIHSS at discharge were observed for both subgroups. Accordingly, similar to prior studies ADAPT showed better to slightly improved discharge outcomes in comparison to other techniques.33–35 Emphasizing the superiority of clinical outcomes utilizing ADAPT, multivariate analysis of 90-day outcome predictors showed PC in comparison to ADAPT was negatively associated with good 90-day outcomes. This is consistent with previously published institutional experiences primarily looking at outcomes for LVO.14,38 Interestingly, in a prior study by Pampana et al., PC showed superior endovascular outcomes when used as a salvage strategy after failed ADAPT. 39 It is important to mention that there are no prior data comparing PC to ADAPT specifically in distal vessel occlusion. Also, while procedure time was independently validated in multivariate modeling to relate to outcomes, it is worth mentioning that there were significant differences in procedure time for the three techniques, with ADAPT having the shortest duration. Intrinsic to ADAPT is a shorter procedure time as (1) the clot does not have to be crossed with a microcatheter, and (2) the time to deploy the SR is not required.
Limitations
There are a number of limitations given the retrospective design of the study. There is no medical control group (IVT)—based on the design of the registry—and thus the added benefit of MT in this cohort in comparison to maximal medical management alone cannot be established. Yet, there are emerging data for distal anterior 40 and posterior41,42 cerebral artery occlusions, as well as distal vessel occlusions overall 43 that compares medical therapy to MT with essentially all analyses showing equipoise and comparable outcomes. Patient selection for MT as well as choice of technique was determined based on the neurointerventionalists experience on a case-by-case basis and with institutional bias. Thus, there is some variability in how centers and interventionalists enroll patients in MT, particularly in this “off label” low NIHSS subgroup. It is conceivable that patients with more difficult-to-navigate, tortuous cerebrovascular anatomy and with more comorbidity and higher risk of complications were excluded and that may skew the data. In addition, these data are collected from primarily academic, high-volume centers and thus generalization to all practice settings should be considered cautiously. Another limitation of the retrospective design is that the registry is limited to the parameters that are collected upfront. So for example, while the use of intracranial angioplasty is collected (and analyzed here), and we presume during this analysis that this is due to underlying ICAD, routine angiographic analysis of these patients was not feasible or performed and thus neither is there reliable information on each patient's collateral perfusion, which can be multifactorial and perhaps related to genetics or ethnicity. Nor is there data regarding whether or not stenting was required after ICA angioplasty. While these data show promising results of MT for patients with minor stroke due to distal vessel occlusion using ADAPT, establishing superiority can only be achieved through a randomized controlled trial.
Conclusions
Mechanical thrombectomy appears to be a safe, effective treatment for patients with minor strokes involving both proximal and distal vessel occlusions. ADAPT shows superior immediate and 90-day clinical outcomes in comparison to other techniques with a similar safety profile for both proximal and distal vessel occlusions.
Supplemental Material
Supplemental material, sj-docx-1-ine-10.1177_15910199231196451 for The effect of occlusion location and technique in mechanical thrombectomy for minor stroke by Isaac Josh Abecassis, Eyad Almallouhi, Reda M. Chalhoub, Ahmed Helal, Janki R. Naidugari, Sami Al Kasab, Eric Bass, Dale Ding, Vasu Saini, Joshua D. Burks, Ilko L. Maier, Pascal Jabbour, Joon-Tae Kim, Stacey Wolfe, Ansaar Rai, Marios-Nikos Psychogios, Edgar Samaniego, Adam S. Arthur, Shinichi Yoshimura, Brian Howard, Ali Alawieh, Isabel Fragata, Hugo Cuellar, Adam Polifka, Justin Mascitelli, Joshua Osbun, Roberto Crosa, Charles Matouk, Min S. Park, Michael R. Levitt, Travis Dumont, Richard W. Williamson, Alejandro M. Spiotta and Robert M. Starke in Interventional Neuroradiology
Footnotes
The author(s) declared no potential conflicts of interest with respect to the research, authorship, and/or publication of this article.
Funding: The author(s) received no financial support for the research, authorship, and/or publication of this article.
ORCID iDs: Ahmed Helal https://orcid.org/0000-0003-3746-3685
Stacey Wolfe https://orcid.org/0000-0001-7603-2728
Adam S. Arthur https://orcid.org/0000-0002-1536-1613
Isabel Fragata https://orcid.org/0000-0002-7037-7458
Hugo Cuellar https://orcid.org/0000-0002-8348-4535
Charles Matouk https://orcid.org/0000-0003-3234-9541
Min S. Park https://orcid.org/0000-0003-1966-8863
Supplemental material: Supplemental material for this article is available online.
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Supplementary Materials
Supplemental material, sj-docx-1-ine-10.1177_15910199231196451 for The effect of occlusion location and technique in mechanical thrombectomy for minor stroke by Isaac Josh Abecassis, Eyad Almallouhi, Reda M. Chalhoub, Ahmed Helal, Janki R. Naidugari, Sami Al Kasab, Eric Bass, Dale Ding, Vasu Saini, Joshua D. Burks, Ilko L. Maier, Pascal Jabbour, Joon-Tae Kim, Stacey Wolfe, Ansaar Rai, Marios-Nikos Psychogios, Edgar Samaniego, Adam S. Arthur, Shinichi Yoshimura, Brian Howard, Ali Alawieh, Isabel Fragata, Hugo Cuellar, Adam Polifka, Justin Mascitelli, Joshua Osbun, Roberto Crosa, Charles Matouk, Min S. Park, Michael R. Levitt, Travis Dumont, Richard W. Williamson, Alejandro M. Spiotta and Robert M. Starke in Interventional Neuroradiology