Factors Associated With Improved Technical Outcomes When Using 0.068‐ to 0.074‐Inch Aspiration Catheters: Analysis From a Multicenter Retrospective Cohort

Abstract

Background

In addition to enlarging the catheter tip diameter, recent aspiration catheters were designed with a novel angled‐tip design. We aimed to evaluate the efficacy of new‐generation angled‐tip aspiration catheters in comparison to commonly used straight‐tip large‐bore aspiration catheters.

Methods

We performed a multicenter retrospective analysis of consecutive cases with M1 occlusion treated with aspiration thrombectomy from July 2016 to February 2021. Patients were divided into 2 cohorts: those in whom a 0.071‐inch angled‐tip catheter was used and those in whom a 0.068‐ to 0.074‐inch flat‐tip catheter was used.

Results

A total of 384 patients were identified. The angled‐tip catheter was used in 129 (33.6%) patients, whereas 255 (66.4%) patients were treated with flat‐tip catheters. There was no significant difference in age, sex, baseline modified Rankin scale score, side of occlusion, initial National Institutes of Health Stroke Scale score, time from last known normal to access, or rate of intravenous recombinant tPA (tissue‐type plasminogen activator) administration. Use of the angled‐tip reperfusion catheter was associated with average 5‐minute faster time to Thrombolysis in Cerebral Infarction 2B or better (22.13±21.05 versus 27±24.54 minutes; P=0.012) and 7‐minute faster time to final recanalization (25.85±25.22 versus 32.96±29.26 minutes; P=0.011). There was no difference in the rate of good outcome or hemorrhagic transformation.

Conclusions

We report a multicenter, retrospective review of patients treated with current generation large‐bore aspiration catheters. Angled‐tipped catheters were associated with shorter times to Thrombolysis in Cerebral Infarction 2B and final reperfusion. There were no differences in 90‐day modified Rankin scale score, rates of intracranial hemorrhage, or complications.

Nonstandard Abbreviations and Acronyms

ECASS

European Cooperative Acute Stroke Study

ICH

intracranial hemorrhage

mRS

modified Rankin scale

TICI

Thrombolysis in Cerebral Infarction

Clinical Perspective

• Newer catheters have been designed to provide larger catheter tip diameters, as there is evidence suggesting that suction force at the tip of a catheter has a significant impact on the success of aspiration thrombectomy, and the force at the catheter tip is directly proportional to the cross‐sectional area of the catheter tip.

• Use of the angled‐tip reperfusion catheter was associated with average 5‐minute faster time to Thrombolysis in Cerebral Infarction 2B or better and 7‐minute faster time to final recanalization.

• There was no significant difference in the rate of good or poor clinical outcome between the angled‐ and flat‐tipped groups; more studies are needed to evaluate potential reasons for this.

Several trials have established the efficacy of mechanical thrombectomy as a treatment option in patients with large‐vessel occlusions. ¹ , ² , ³ , ⁴ , ⁵ , ⁶ , ⁷ , ⁸ Although multiple thrombectomy techniques have been described using stent retrievers as a first‐line device, direct contact aspiration has become an accepted alternative to stent retriever–based techniques, with a comparable recanalization rate. ⁹ , ¹⁰ , ¹¹ , ¹² , ¹³ , ¹⁴ Direct contact aspiration uses large‐bore catheters to aspirate the thrombus, and if unsuccessful, provides a platform for delivery of other devices, such as stent retrievers, stents, and angioplasty balloons. ¹⁵ , ¹⁶ , ¹⁷

There is evidence suggesting that suction force at the tip of a catheter has a significant impact on the success of aspiration thrombectomy, and the force at the catheter tip is directly proportional to the cross‐sectional area of the catheter tip (pressure is the ratio of force/area). ¹⁸ , ¹⁹ , ²⁰ Thus, newer catheters have been designed to provide larger catheter tip diameters. ²⁰ , ²¹ , ²² , ²³ , ²⁴ , ²⁵ , ²⁶ In addition to enlarging the catheter tip diameter, recent catheters were designed with a novel angled‐tip design to maximize clot engagement area. ²⁷ We aimed to evaluate the efficacy of new‐generation angled‐tip aspiration catheters in comparison to commonly used straight‐tip large‐bore aspiration catheters in a real‐world data set.

Methods

The data that support the findings of this study are available from the corresponding author on reasonable request.

Data Collection

We performed a multicenter retrospective analysis of patients with acute ischemic stroke treated with endovascular therapy after obtaining institutional review board approval in each participating center. Ten high‐volume, Comprehensive Stroke Centers participated. Operators contributed consecutive cases with M1 occlusion treated with mechanical thrombectomy from July 2016 to February 2021. Patient‐specific data included age, sex, gender, admission National Institutes of Health Stroke Scale score, and baseline modified Rankin scale (mRS) score. Preprocedure data consisted of side of occlusion, whether the patient received intravenous recombinant tPA (tissue‐type plasminogen activator), and time from last known well to access. Procedural data consisted of location of vascular access, the use of conscious sedation or general anesthesia, the primary aspiration catheter used, modified Thrombolysis in Cerebral Infarction (TICI) score after first pass and at the end of the procedure, number of passes to achieve TICI 2B or better, TICI 2C or better, and final recanalization, whether a stent retriever was used as a second‐line device, time to recanalization, presence of downstream emboli, and presence of emboli to new territory. ²⁸ Postprocedural data collected were discharge National Institutes of Health Stroke Scale score, National Institutes of Health Stroke Scale and mRS scores at 90 days, the presence of intracranial hemorrhage (ICH) on follow‐up imaging, and periprocedural and postprocedural complications. ICH was scored according to the ECASS (European Cooperative Acute Stroke Study) III scoring system when possible. ²⁹ All data were self‐adjudicated.

Not all centers rated reperfusion using the TICI 2C scoring. In some instances, these data could be extrapolated (ie, in the case of a single‐pass resulting in a final recanalization of TICI 3, the time to final recanalization was used as a surrogate for time to TICI 2C or better). Likewise, if 2 passes were performed to achieve a final recanalization of TICI 3 and the first pass resulted in a recanalization of TICI 2B, then the number of passes and time to achieve TICI 2C or better were assumed to be the same as for final recanalization. In cases in which the final recanalization was not 3 and >2 passes were made, no assumptions were made.

Outcome Measures

Angiographic Outcomes

The rate of TICI2b or better recanalization was defined as good angiographic outcome, whereas TICI2c or better was defined as excellent angiographic outcome. We also used access time to recanalization and average number of passes to achieve recanalization as angiographic outcome measures.

Clinical Efficacy Outcome

We defined 90‐day mRS score of 0 to 2 as good outcome and mRS score >2 as poor outcome.

Clinical Safety Outcome

The rate of ICH calculated on the basis of ECASS III criteria was used as safety outcome, including petechial hemorrhagic transformations (HI‐1 and HI‐2) and parenchymal hemorrhages (PH‐1 and PH‐2).

Statistical Analysis

Patients were divided into 2 cohorts: those in whom a 0.071‐inch angled‐tip Zoom71 catheter (Imperative Care, Campbell, CA) was the initial device used to attempt reperfusion and those in whom a 0.068‐ to 0.074‐inch flat‐tip (nonangled) catheter was the initial device used to attempt reperfusion. Patient characteristics and periprocedural and postprocedural metrics were compared.

Continuous variables are reported as mean±SD or median (interquartile range) and were tested using a Wilcoxon rank‐sum test. Discrete variables are reported as number (percentage) and were tested using Fisher exact test. Values of P<0.05 were considered statistically significant. All analyses were performed with the Julia programming language, version 1.6.1, using the StatsKit package.

Statistical analysis was repeated including only cases from 2018 onwards to mitigate any effect of improvements in techniques over time.

Results

A total of 384 patients with acute M1 occlusion who underwent thrombectomy were identified. The angled‐tip catheter was used in 129 (33.6%) patients, whereas 255 (66.4%) patients were treated with flat‐tip aspiration catheters (Table 1).

Table 1.

Summary of Catheters Used

Catheter	Company	Size, inches	No.
Angled tip
Zoom71	Imperative Care, Campbell, CA	0.071	129
Flat tip
ACE68	Penumbra, Alameda, CA	0.068	91
Jet7	Penumbra, Alameda, CA	0.072	111
Sofia Plus	Microvention, Aliso Viejo, CA	0.070	18
React71	Medtronic, Minneapolis, MN	0.071	21
Large‐bore catheter	Cerenovus, Irvine, CA	0.071	8
Vecta	Stryker Neurovascular, Kalamazoo, MI	0.074	6

Baseline Patient and Preprocedural Characteristics

There was no significant difference between the 2 groups in terms of age, sex, baseline mRS score, side of occlusion, initial National Institutes of Health Stroke Scale score, time from last known normal to access, or rate of intravenous tPA administration. There was a significantly higher proportion of tandem occlusions in the angled‐tip cohort (5.15% versus 0.48%; P=0.027) (Table 2).

Table 2.

Baseline Patient and Preprocedural Characteristics for Each Cohort

Characteristic	Angled‐tip cohort	Flat‐tip cohort
Total No.	129	255	P value
Age, mean±SD, y (N)	65.7±13.84 (119)	67.9±14.43 (234)	0.12
Female sex, N/total (%)	62/129 (48.1)	133/255 (52.2)	0.52
Baseline mRS score, median/IQR (N)	1.0/2.0 (127)	0.0/2.0 (237)	0.36
Initial NIHSS score, mean±SD (N)	16.19±6.78 (129)	16.57±6.25 (249)	0.47
Received intravenous tPA, N/total (%)	50/128 (39.1)	92/253 (36.4)	0.69
Right side lesion, N/total (%)	62/129 (48.1)	121/255 (47.5)	1.0
Tandem occlusion, N/total (%)	5/97 (5.15)	1/207 (0.483)	0.027*
LKN to access, mean±SD, min (N)	259.0±310.94 (91)	290.48±331.19 (221)	0.16

IQR indicates interquartile range; mRS, modified Rankin scale; NIHSS, National Institutes of Health Stroke Scale; tPA, tissue‐type plasminogen activator; and LKN, last known normal.

^* Denotes statistical significance.

Angiographic Outcomes

Use of the angled‐tip reperfusion catheter was associated with average 5‐minute faster time to TICI 2B or better (22.13±21.05 versus 27±24.54 minutes; P=0.012) and 7‐minute faster time to final recanalization (25.85±25.22 versus 32.96±29.26 minutes; P=0.011). There were no significant differences in rates of good and excellent recanalization or number of passes to achieve recanalization between cohorts. Most cases in both cohorts were performed via femoral access and with conscious sedation, with no significant difference between the groups. There was also no difference in stent retriever use, reported emboli to new territory, downstream emboli, or procedural complications (Table 3). When only cases from January 2018 onwards were selected, the angled‐tipped group remained associated with a faster time from access to TICI 2B or better (22.13±21.05 versus 27.6±25.5 minutes; P=0.012) and final recanalization (25.85±25.22 versus 33.76±30.31 minutes; P=0.011).

Table 3.

Procedural Characteristics and Angiographic Results

Variable	Angled‐tip cohort	Flat‐tip cohort
Total No.	129	255	P value
Procedural characteristics, N/total (%)
Femoral access	126/129 (97.7)	251/255 (98.4)	0.87
Conscious sedation	101/128 (78.9)	219/254 (86.2)	0.096
Stent retriever	26/126 (20.6)	47/234 (20.1)	1.0
Emboli to new territory	0/125 (0.0)	6/225 (2.67)	0.14
Downstream emboli	20/113 (17.7)	36/145 (24.8)	0.22
Procedural complications	6/129 (4.65)	8/255 (3.14)	0.63
Final TICI, N/total (%)
TICI 2B	34/129 (26.4)	68/254 (26.8)	1.0
TICI 2C	27/129 (20.9)	36/254 (14.2)	0.13
TICI 3	63/129 (48.8)	139/254 (54.7)	0.33
TICI 2B or better	124/129 (96.1)	243/254 (95.7)	1.0
TICI 2C or better	90/129 (69.8)	175/254 (68.9)	0.96
No. of passes to recanalization, median/IQR (N)
2B or better	1.0/1.0 (123)	1.0/1.0 (241)	0.58
2C or better	1.0/1.0 (99)	1.0/1.0 (181)	0.98
Final recanalization	1.0/1.0 (126)	1.0/2.0 (255)	0.95
First‐pass efficacy, N/total (%)
First‐pass TICI 2B or better	85/129 (65.9)	174/254 (68.5)	0.69
First‐pass TICI 2C or better	90/129 (69.8)	175/254 (68.9)	0.96
Time from access to recanalization, mean±SD, min (N)
2B or better	22.13±21.05 (115)	26.99±24.54 (235)	0.012*
2C or better	19.41±13.91 (83)	17.79±11.36 (92)	0.9
Final recanalization	25.85±25.22 (121)	32.96±29.26 (246)	0.011*

IQR indicates interquartile range; and TICI, Thrombolysis in Cerebral Infarction.

^* Denotes statistical significance.

Clinical Outcomes

There was no significant difference in the rate of good or poor clinical outcome between the angled‐ and flat‐tipped groups. There were no statistically significant differences in rate of hemorrhagic transformation between the 2 cohorts. Of the 95 reported postprocedural hemorrhages, 75 (78.9%) were scored according to the ECASS III hemorrhage grade. ³⁰ There were significantly fewer hemorrhagic transformations (HI‐1 and HI‐2) in the angled‐tipped cohort (14.6% versus 25.3%; P=0.026), and no reported parenchymal hemorrhages (PH‐1 or PH‐2) for either group (Table 4).

Table 4.

Summary of Outcomes Between the 2 Group

Variable	Angled‐tip cohort	Flat‐tip cohort
Total No.	129	255	P value
Discharge NIHSS score, mean±SD (N)	8.13±8.7 (87)	9.01±10.23 (199)	0.54
90‐d mRS score			0.86
0–2, N/total (%)	33/79 (41.8)	40/118 (33.9)
3–6, N/total (%)	46/79 (58.2)	78/118 (66.1)
ICH, N/total (%)	30/123 (24.4)	65/225 (28.9)	0.44
Scored ICH (ECASS), N/total (%)	18/123 (14.6%)	57/225 (25.3%)	0.026*
HI‐1	11/123 (8.9)	31/225 (13.8)
HI‐2	7/123 (5.7)	26/225 (11.6)
PH‐1	0/123 (0)	0/255 (0)
PH‐2	0/123 (0)	0/255 (0)

ECASS indicates European Cooperative Acute Stroke Study; HI, hemorrhagic transformation; ICH, intracranial hemorrhage; mRS, modified Rankin scale; NIHSS, National Institutes of Health Stroke Scale; and PH, parenchymal hemorrhage.

^* Denotes statistical significance.

Discussion

We sought to investigate the factors associated with technical outcomes in a multicenter, retrospective cohort of M1 occlusions, using a variety of current‐generation large‐bore aspiration catheters. Our results demonstrate that angled‐tipped aspiration catheters were associated with a significantly faster access time to TICI 2B and final recanalization, despite the higher proportion of tandem occlusions in the angled‐tip catheter cohort. This supports an earlier report that associates the use of an angled‐tipped catheter with better technical outcomes; however, improved clinical outcomes were not observed in this multicenter study. In the original report, we theorized that time to recanalization was faster with the beveled tip because of a higher force at the tip, thus allowing better clot ingestion, as well as a better angle of interaction with the clot, both of which have been shown to improve efficacy of thrombectomy. ²⁷ Despite evidence demonstrating the positive impact of shorter procedural times on outcomes, there was no difference in 90‐day mRS score between the flat‐ and angled‐tipped cohorts. ³¹ , ³² TICI 2C remains a controversial metric, and many centers do not report TICI 2C recanalization, instead using TICI 2B or better as a target for successful reperfusion despite evidence that TICI 2C or better has a better predictive value for improved outcomes. ³³ , ³⁴ , ³⁵

To evaluate the potential effect of improving experience over time leading to improved speed of recanalization in our more recent angled‐tip cases, we compared procedure times from August 2016 to February 2021 with those from January 2018 to February 2021 and found that even when excluding cases from before January 2018, there remained a significant difference in time to TICI 2B and final recanalization between angled‐ and flat‐tipped catheters.

The rate of hemorrhage on follow‐up was 24.4% in the angled‐tip group and 28.9% in the flat‐tipped group, which was not statistically significant (P=0.44). However, these rates are higher than the reported rate of symptomatic ICH following mechanical thrombectomy. ³⁶ , ³⁷ , ³⁸ We report both symptomatic and radiographic ICH, and not all centers reported ICHs in using the ECASS score. Any blood products on a heme‐sensitive magnetic resonance imaging sequence were reported as hemorrhage in this study, although most were asymptomatic. Contrast staining has been reported in 23% to 84% of patients, and it may represent a significant proportion of our reported ICH rate. ³⁹ In many centers, follow‐up imaging is performed using noncontrasted head computed tomography scans. In these cases, if there is no pressing need to distinguish contrast staining from parenchymal hemorrhage (PH‐1) ECASS hemorrhage, further investigation with magnetic resonance imaging or serial head computed tomography scans may not be performed. As postthrombectomy imaging becomes more routine, it will become more important to identify contrast staining versus true ICH in a resource‐conscious manner. Finally, there were no reported parenchymal hemorrhages (PH‐1 or PH‐2) in either cohort, underscoring the safety of aspiration thrombectomy.

Limitations

There are several limitations to our study. First, this was a retrospective analysis of self‐reported data from many centers with multiple operators. There is significant variability in the grading of the TICI score, and TICI 2C was not consistently used by many centers. Second, there are subtle variations between operators’ techniques that are difficult to capture. The definition of a thrombectomy pass remains ill defined and open to debate. Some operators opt to cross the lesion with wires and microcatheters, whereas others do not, citing concerns of clot fragmentation. ⁴⁰ Third, we report on catheters that were used to successfully perform a thrombectomy attempt, not ones that failed to navigate to the lesion. Although the navigability of the aspiration catheters may be reflected in the time to recanalization, attention should be given to rates of catheter navigation failure as well. Furthermore, data on the type of arch were not routinely collected at all sites and were thus not available for analysis. Finally, our primary aim was to examine the efficacy of aspiration catheters and, as such, we did not examine the relationship between aspiration catheter performance and the use of different guide catheters, such as balloon guides. Further research is needed to clarify the role of guide catheters in aspiration thrombectomy. However, all centers used their usual practice patterns for thrombectomy and, as such, this represents real‐world experience.

Conclusions

We report a real‐world, multicenter, retrospective review of 384 patients presenting with an acute ischemic stroke attributable to M1 occlusions treated with current‐generation large‐bore aspiration catheters using aspiration first techniques. Angled‐tipped catheters were associated with a shorter time to TICI 2B and final reperfusion. There were no differences in 90‐day mRS score, rates of ICH, or complications between flat‐ and angled‐tipped cohorts.

Sources of Funding

None.

Disclosures

Several authors of this paper have competing interests that include consulting positions, stock options and/or service on advisory boards.

JV owns stock in Viz.AI, Imperitive Care and is a consultant for Medtronic, Cerenovus, Imperitive Care, QApel, Viz.AI, and Avail. RT is employed by Siemens Healthineers, has equity in Q'Apel, Echovate, Endostream, NEAR Center, and is a consultant for Medtronic, Cerenovus. JM is on the steering committee for the Imperitive Care trial, as well as a consultant for Microvention. RH is a consultant for Medtronic, Stryker, Cerenovous, Microvention, Balt, Phenox, Rapid Medical, and Q'Apel, and is on advisory board for MiVI, eLum, Three Rivers, Shape Medical and Corindus. Unrestricted research grant from NIH, Interline Endowment, Microvention, Stryker, CNX, and is an investor/stockholder for InNeuroCo, Cerebrotech, eLum, Endostream, Three Rivers Medical Inc, Scientia, RisT, BlinkTBI, and Corindus. RD is a consultant and PI for Imperative Care. IC owns stock in Imperative Care and Q'Apel, and is a consultant for Imperative Care, Microvention, Medtronic, Cerenovus, and Q'Apel. MM has an NIH grant, owns stock options in BrainQ,Endostream, Serenity medical, Synchron, QAS.AI, Quantanosis.AI, and is a consultant for Cerenovus and Medtronic. AS has an NIH research grant, and financial Interest/Investor/StockOptions/Ownership: Adona Medical, Inc., Amnis Therapeutics, Bend IT Technologies, Ltd., BlinkTBI, Inc, Cerebrotech Medical Systems, Inc., Cerevatech Medical, Inc., Cognition Medical, CVAID Ltd., E8, Inc., Endostream Medical, Ltd, Galaxy Therapeutics, Inc., Imperative Care, Inc., InspireMD, Ltd., Instylla, Inc., International Medical Distribution Partners, Launch NY, Inc., NeuroRadial Technologies, Inc., NeuroTechnology Investors, Neurovascular Diagnostics, Inc., Peijia Medical, PerFlow Medical, Ltd., Q'Apel Medical, Inc., QAS.ai, Inc., Radical Catheter Technologies, Inc., Rebound Therapeutics Corp. (Purchased 2019 by Integra Lifesciences, Corp), Rist Neurovascular, Inc. (Purchased 2020 by Medtronic), Sense Diagnostics, Inc., Serenity Medical, Inc., Silk Road Medical, Sim & Cure, SongBird Therapy, Spinnaker Medical, Inc., StimMed, LLC, Synchron, Inc., Three Rivers Medical, Inc., Truvic Medical, Inc., Tulavi Therapeutics, Inc., Vastrax, LLC, VICIS, Inc., Viseon, is a consultant/advisor for: Amnis Therapeutics, Apellis Pharmaceuticals, Inc., Boston Scientific, Canon Medical Systems USA, Inc., Cardinal Health 200, LLC, Cerebrotech Medical Systems, Inc., Cerenovus, Cerevatech Medical, Inc., Cordis, Corindus, Inc., Endostream Medical, Ltd, Imperative Care, InspireMD, Ltd., Integra, IRRAS AB, Medtronic, MicroVention, Minnetronix Neuro, Inc., Peijia Medical, Penumbra, Q'Apel Medical, Inc., Rapid Medical, Serenity Medical, Inc., Silk Road Medical, StimMed, LLC, Stryker Neurovascular, Three Rivers Medical, Inc., VasSol, Viz.ai, Inc, and is a national PI/steering committee for Cerenovus EXCELLENT and ARISE II Trial; Medtronic SWIFT PRIME, VANTAGE, EMBOLISE and SWIFT DIRECT Trials; MicroVention FRED Trial & CONFIDENCE Study; MUSC POSITIVE Trial; Penumbra 3D Separator Trial, COMPASS Trial, INVEST Trial, MIVI neuroscience EVAQ Trial; Rapid Medical SUCCESS Trial; InspireMD C GUARDIANS IDE Pivotal Trial.