Macrowire for intracranial thrombectomy: An early experience of a new device and technique for anterior circulation large vessel occlusion stroke

Abstract

Background and Purpose

Mechanical thrombectomy (MT) has become the standard of care for treatment of acute ischemic stroke secondary to large vessel occlusion up to 24 h from the last known normal time. With ADAPT and SOLUMBRA techniques, classically, a large bore aspiration catheter is delivered over a microcatheter and microwire crossing the clot to perform thrombectomy. Recently, a novel macrowire (Colossus 035 in.) has been introduced as a potential alternative to the use of microwire-microcatheter to allow the delivery of the aspiration catheter (ID = 0.070 in. up to 0.088 in.) over a macrowire alone.

Objective

To test the feasibility of delivering an aspiration catheter to clot interface over a macrowire alone.

Materials and Methods

A retrospective evaluation of prospectively maintained Macrowire for Intracranial Thrombectomy (MINT) Registry where this novel technique was utilized for thrombectomy. Consecutive patients undergoing MT using the MINT technique were included. We collected baseline demographics, imaging and clinical characteristics, rate of procedural success, conversion to traditional MT, and complications.

Results

Fifty consecutive patients were recruited during the initial 4 months of the larger study duration. The aspiration catheter was able to be advanced to the clot interface successfully in 46/50 (92%) using the MINT technique. Median time from vascular access to the first pass was 11.30 min (IQR = 7.45–14.30 min) and successful thrombectomy was 14 min (IQR = 10–22.15). The modified first-pass effect with this procedure was 71%. One vasospasm was reported as a procedural complication.

Conclusions

MINT is safe and feasible for large vessel occlusion recanalization based on our initial clinical experience in this multicenter study.

Introduction

Mechanical Thrombectomy has become the cornerstone therapy to achieve reperfusion in large vessel occlusion causing acute ischemic stroke.^1,2 Although pivotal clinical trials were used and guidelines recommended stent retrievers use to perform MT, a direct aspiration first pass technique (ADAPT) was proven to be noninferior to the stent retriever (SOLUMBRA) technique in the COMPASS trial.^2,3 Now, the ADAPT and SOLUMBRA techniques are the most commonly utilized techniques for MT the world over.^3,4,5 The success of ADAPT in part has led to significant development of catheter technology. With remarkable success in reducing morbidity, the procedural volumes have increased with the continued expansion of indications for MT. Increased volumes have allowed for developing focus on making thrombectomy safer, faster, and more widely available. Although significant strides have been made in newer and more trackable devices, both these techniques have largely remained unchanged in the last two decades. In both techniques, a triaxial setup is utilized to deliver an aspiration catheter over a microcatheter and microwire through a support base catheter. In both techniques^3,4,5 the clot is crossed with the help of a microwire and microcatheter to allow an advancing aspiration catheter or to deploy a stent retriever through a microcatheter. Crossing the clot raises multiple technical challenges like possible microwire perforation in view of no distal roadmap post occlusion, plaque disruption with underlying intracranial atherosclerosis, and possible distal new territory embolization secondary to clot disruption. Distal embolization has remained a common complication of endovascular treatment of proximal large vessel occlusion with rates even in recent trials up to 50.6%. ⁶ Clot disruption while performing a thrombectomy is further increased by more thrombectomy passes, long clots, and clot makeup. ⁶ Recently, Aristotle Colossus macrowire (Scientia Vascular, Inc. West Valley City, UT, USA) became the first 0.035 in. macrowire to receive United States Food and Drug Administration (US FDA) approval for neurovascular purposes. We hypothesized delivering an aspiration catheter to the clot/thrombus over the macrowire alone without the traditional use of microcatheter and microwire is feasible. Advantages of using a macrowire over the traditional technique include lesser chances of wire perforation by going blind without roadmap post clot, clot, or plaque disruption, streamlining setup, and avoiding additional costs for microcatheter and microwire with the potential to reduce procedure times. In addition to the above, there is a potential to increase safety by avoiding the selection of small perforators and this prevents microwire perforations with this adaptation. We believe the catheter sizes that can be delivered using this device/technique is wide ranging from ID: 0.038–0.088 in. but can be more challenging as the ID/size of the ledge effect keeps on increasing making it difficult to deliver the large and ultra-large bore catheters.

We describe the Macrowire for Intracranial Thrombectomy (MINT) technique, performing ADAPT by delivering aspiration/reperfusion catheter to the clot interface over the Colossus macrowire alone across multiple high-volume centers.

Materials and methods

Overview of the study design

The MINT Registry is a multicenter, observational study with a focus on understanding the delivery of aspiration catheter over a novel macrowire (Colossus 0.035 in. Scientia Vascular, Inc. West Valley City, UT, USA) to clot interface without clot disruption. The rationale and design of the registry have been published earlier. ⁷ Standard definition of anterior circulation large vessel occlusion was employed to include carotid terminus and middle cerebral artery (MCA) M1 segment.^1,2 The MINT technique aims to provide data on the feasibility of performing MT with the delivery of an aspiration catheter over a macrowire alone. The sites were selected from high-volume centers that had used this macrowire at least for three successful neurovascular cases and performed “ADAPT first” for MT. This study is an early experience of the first 50 cases done as a part of this registry.

Population

Investigators at all individual sites will screen and collect data on patients who meet the following inclusion and exclusion criteria.

Inclusions

1. Age 18–85 years

2. Time of onset 0–24 h

3. Acute stroke patient with NIHSS ≥ 6

4. CT-ASPECTS ≥ 6

5. Evidence of proximal anterior circulation intracranial occlusion on noninvasive imaging

6. Baseline Modified Rankin score: 0–2

Exclusion

1. Age <18 years or >85 years

2. Unknown time of onset

3. NIHSS ≤ 5

4. CT ASPECTS ≤5

5. Prestroke morbidity, modified Rankin score > 2

6. Tandem occlusion

7. MCA-M2/M3 occlusions

MINT technique

The selection of aspiration catheters was left to the operators to select whatever was the local standard to test our hypothesis in the most pragmatic, realistic true world experience. The aspiration catheters were to be advanced over the macrowire (Colossus 0.035 in. Scientia Vascular, Inc. West Valley City, UT, USA) to the clot interface and the clot was not to be crossed by the macrowire. Local protocol for aspiration was followed to complete MT. It was considered a failure if the aspiration catheter could not be advanced to the thrombus over a macrowire alone. As operators did not have experience with this product before, the consensus was to avoid crossing the clot to avoid inadvertent dissection or perforation by advancing the macrowire blind post thrombus. In addition, if there was a failure to advance the aspiration catheter to the clot interface, the decision to switch set-up was left to the operator which included the use of a stent retriever or the use of microwire and microcatheter to perform thrombectomy. As this was a learning experience for all operators, we requested the operators to make subsequent passes after the first attempt per local standards to switch techniques or setups and gathered that information. A representative video of the MINT technique is attached as a supplementary file (Video 1).

Variables collected

Variables collected include demographics, stroke risk factors, premorbid condition, baseline National Institute of Health Stroke Scale (NIHSS), and follow-up imaging data. We collected NIHSS at discharge and a modified Rankin Scale was obtained from follow-up clinic data where available. All radiologic and angiographic details were self-adjudicated including the thrombolysis in cerebral ischemia (TICI) scale.

Descriptive statistics were used to present the data using the mean, standard deviation, and median with interquartile range or frequency distribution as appropriate.

Results

Baseline patient characteristics

A total of the first 50 MT procedures utilizing the MINT technique were performed at six hospitals from June 2023 for a period of 6 months. Patient and procedural characteristics are described in Table 1. The patients included had slight male preponderance (52%) with a median age of 70 years (IQR = 64–76.3 years). Intravenous thrombolysis was performed in 32% of patients and the median time from last known well time to vascular access was 347 min (IQR = 163.75–814.5 min). NIHSS at presentation was 18 (IQR = 14–24). General anesthesia was utilized in 52% of cases and most cases were performed via femoral access (96%). 16% (8/50) of cases were terminus occlusions and the rest were MCA-M1 occlusion cases. In cases where etiology was determined, atrial fibrillation was responsible for 50% of cases in this sample (n = 25/50). Other etiologies were ICAD in 6% of cases, patent foramen ovale, malignancy, aortic valve growth, and heart failure were responsible for the rest of 12% of cases. Embolic stroke of unknown source was responsible for 32% of cases.

Table 1.

Patient and procedural characteristics

Patient characteristics
Age (median)	70.0 years (64.0–76.3 years IQR)
Female	24/50 (48.0%)
Hypertension	41/50 (82.0%)
Hyperlipidemia	32/50 (64.0%)
Diabetes mellitus	19/50 (38.0%)
Atrial fibrillation	18/50 (36.0%)
Hypercoagulable condition	6/50 (12.0%)
Known chronic heart failure	8/50 (16.0%)
Previous stroke	8/50 (16.0%)

*3 unknown last seen well times

Angiographic and imaging results

The MINT technique was successful in delivering an aspiration catheter to the clot interface in 92% of cases (n = 46/50). The median time for vascular access to the first pass is 11.30 min (IQR = 7.45–14.30 min) with the first pass to recanalization in 14 min (IQR = 10.00–22.15 min). Successful MT was performed with an average of 1.5 passes (range = 1–5) with 71.7% achieving TICI3 recanalization with TICI2c in 15.22% and TICI2b in 13%, respectively. There was a failure to perform the MINT technique in four cases characteristics described in Tables 2 and 3. In all four cases where there was MINT failure, adjunctive devices were required to perform thrombectomy. The first-pass effect was 52% and the modified first-pass effect was 71% (n = 33/46) with this technique. In five patients, there was a switchover to the SOLUMBRA technique after at least one pass, and in other cases, more passes with the same setup resulted in successful recanalization. Three people died: one secondary to pulmonary embolism on day 14 and two secondary to families deciding comfort care. In all cases of MINT, there was no distal embolization to any new territory. Table 4 includes information on all aspiration catheters included in the study.

Table 2.

Macrowire performance characteristics

0.035 in Macrowire performance characteristics
	Successful delivery of aspiration catheter with guidewire alone	Failure to deliver—microcatheter bailout required	P-values
	46/50 (92.0%)	4/50 (8.0%)
Median access to first pass time	11:30 min (7:45–14:30 min IQR)	36:00 min (27:15–38:00 min IQR)	P < .0001
Median number of passes	1 pass (1–2 pass IQR)	1.5 passes (1–3.5 pass IQR)	P = .415
Median access to revascularization Time	14:00 min (10:00–22:15 min IQR)	48:00 min (28:15–68:30 min IQR)	P < .0001
TICI 3	33/46 (71.7%)	1/4 (25.0%)
TICI 2C	7/46 (15.22%)	2/4 (50.0%)
TICI 2B	6/46 (13.0%)	1/4 (25.0%)

Table 4.

Aspiration catheter choice and success with the technique

Aspiration catheter	Success rate (delivery with just the 0.35 in. guidewire)
6F Sofia (Microvention, Tustin, CA)	13/13 (100%)
5F Sofia (Microvention, Tustin, CA)	2/2 (100%)
Cereglide 71(Cerenovus, CA, USA)	2/3 (67%)
Apro 70 (Medtronic Neurovascular, CA, USA)	1/1 (100%)
LBC 71 (Cerenovus, CA, USA)	5/6 (83%)
Red 62 (Penumbra, Inc, USA)	1/1 (100%)
Red 68 (Penumbra, Inc, USA)	2/2 (100%)
Red 72 (Penumbra, Inc, USA)	3/3 (100%)
Zoom 71 (Imperative Care, CA, USA)	16/17 (94%)
Zoom 88 (Imperative Care, CA, USA)	2/3 (67%)

There was no symptomatic posttreatment ICH (increase of NIHSS by more than four points) or PH-2 as defined by ECASS-3 criteria ⁸ : two patients had hemorrhagic infarction type 1 (HI1), four patients had hemorrhagic infarction type 2 (HI2), and one had parenchymal hematoma type 1 (PH-1). Other than one catheter-related spasm, there were no other intraprocedural complications.

There was no difference in case failures or complication rates in the hands of operators who were in the early stage (<5 years from fellowship graduation) or experienced (> 5 years from fellowship graduation).

Clinical results

Out of 50 cases, 42/50 cases had early neurological improvement (ENI) defined as either an improvement in eight or more points in NIHSS or more than 30% improvement in NIHSS. ⁹ Modified Rankin Scale was available for 42/50 cases out of which excellent outcome (mRS 0–1) was reported in 42% of cases and 66% of patients had good outcome (mRS ≤ 2). There were four deaths out of which one was associated with pulmonary embolism and family choosing comfortable care in the remaining three patients.

Discussion

In this study, we report the early real-world experience of a macrowire in delivering an aspiration catheter to the clot interface. This study demonstrates reasonable safety and efficacy with the MINT technique.

• A. Success in delivery of aspiration catheter to clot interface with a new technique to prevent clot disruption:

In our study, an aspiration catheter was successfully delivered over macrowire alone to clot interface in 92% (n = 46/50) cases without crossing the clot (Figure 1). In the four cases where the MINT technique failed, even the traditional ADAPT (microcatheter and microwire setup) did not succeed. In all four cases, the catheters could not be advanced past the ophthalmic origin over the macrowire alone. All four cases needed a stent retriever as a bailout secondary to anatomy or underlying etiology for acute ischemic stroke. Anatomy plays a significant role, and we studied this in detail with internal carotid artery tortuosity described previously in Koge et al. ¹⁰ In all four cases of failure, in one case extra-large bore catheter was used (Zoom 088) as well as (n = 3/4) had coiled ICA with significant cavernous segment tortuosity (Table 3). As compared to previous studies even in the new platforms like Freeclimb 070 which utilizes a Tenzing device to deliver the aspiration catheter to clot interface, in a smaller sample of 30 cases, seven required an additional microwire to deliver the aspiration catheter over Tenzing to the clot interface, but the aspiration catheter delivery with this setup was in 100% cases (n = 30/30). ¹¹ In another contemporary series even delivery of SofiaPlus catheter delivery failed to advance to the clot interface without the use of Wedge (Microvention, Tustin, CA) device in 24.5% of cases (n = 38/155). ¹²

Figure 1.

Representative case to depict the MINT technique. A: Angiogram showing right middle cerebral artery proximal occlusion (black arrow pointing to the proximal MCA occlusion). B: Fluoroscopy snapshot showing macrowire at clot/thrombus interface (red arrow). C. Fluoroscopy snapshot showing macrowire at clot interface (red arrow) and (green arrow) aspiration catheter location when the macrowire is at position before advancing the aspiration catheter over macrowire. D and E: Angiogram showing complete (TICI3) recanalization in anterior-posterior and lateral projections. F: Postthrombectomy diffusion-weighted image showing small infarct volume.

Table 3.

Categories of anatomical feature classification

Categories of anatomical features
	Anatomical features	Successful delivery of aspiration catheter with guidewire alone	Failure to deliver—microcatheter bailout required
Extracranial tortuosity classification	Tortuous	30/46 (65.2%)	2/4 (50.0%)
	Kinked	7/46 (15.2%)	0/4 (0%)
	Coiled	2/46 (4.4%)	2/4 (50.0%)
	Straight	7/46 (15.2%)	0/4 (0%)
ICA tortuosity classification	Type 1	8/46 (17.4%)	1/4 (25.0%)
	Type 2	19/46 (41.3%)	2/4 (50.0%)
	Type 3	16/46 (34.8%)	1/4 (25.0%)
	Type 4	2/46 (4.4%)	0/4 (0%)
Location of occlusion	Right ICA terminus	3/46 (6.5%)	1/4 (25.0%)
	Left ICA terminus	4/46 (8.7%)	0/4 (0%)
	Right M1-M2	21/46 (45.7%)	0/4 (0%)
	Left M1-M2	18/46 (39.1%)	2/4 (50.0%)

We also incorporated a detailed anatomical study based on work by Koge et al.. ¹⁰ Extracranial and cranial tortuosity were both considered. Tortuous and coiled extracranial features in addition to types 1–3 for cavernous segment tortuosity accounted for all four failures out of 50 cases (Table 4). Despite extracranial and cranial anatomic tortuosity, the aspiration catheter was able to be delivered to the clot interface with high success in 92% of patients. We believe consistent reporting of this important feature in further publications of newer generation of devices will be critical to understand the limitations of each platform suitably and allow the operators to choose the right choice for their next case.

• B. Procedural nuances:

By far, the most important procedural benefit of this technique, we believe, is the prevention of microwire perforation in view of no necessity to cross-clot with this macrowire. No distal embolization in a new territory was reported in our sample. Although this is a small sample, we will continue to gather data on all future cases as a part of the MINT Registry to study this effect with a total of 15 sites collecting prospective data. ⁷ Another important benefit of MINT is the relatively quick and easy setup. The time taken to perform the thrombectomy from vascular access to reperfusion is an important marker for device and technique efficacy. COMPASS trial reported a mean/median of 25 min (21–30) with the ADAPT technique and 35 min (30–41 min) with the SOLUMBRA technique. Although this trial was one of the pivotal trials and technology has evolved since the procedure times for later trials like DEFUSE-3 were 38 min (median) (26–59 min) thus not significantly different. ¹³ This technique was comparable to recently published new generation devices like FreeClimb 70 reporting a median time of 12 min for the first pass (8–15 min) as compared to 11.30 for MINT and a median recanalization time of 14 min for MINT as compared to 16 min for FreeClimb70. ¹¹

The utilization of Colossus 35 macrowire also allowed for any choice of aspiration catheters that the operators used regularly and possibly contributed to good timings and outcomes.

Ten different varieties of catheters were used in these first fifty cases highlighting the generalizability of the technique (Table 4) including extra-wide bore or ultra-wide bore catheters (0.088 in.). To our knowledge, this is the first newer generation of devices that democratizes this choice of aspiration catheter for the platform as the comparable platforms either Freeclimb070 or Q’Apel products are packaged components. One patient developed catheter-related vasospasm and did not require any additional treatment. Similarly, the previously discussed small sample study of the Tenzing 7 delivery system had reported no complications. ¹¹ In a recently reported larger sample study of this delivery system 2.3% (n = 4/176) patients had nonflow limiting vessel dissection, and similar numbers were reported for intracranial vessel perforation, which was thought to be unrelated to Tenzing. ¹⁴ Traditional setup has reported up to 2.6% chances of flow limiting vasospasm or vessel dissection from advancing larger aspiration catheters to the thrombus.^5,15 No similar comparative published data exists for the Q’Apel system. The macrowire size helps in avoiding inadvertent small perforator selection and thus dissections and perforations which are otherwise important reasons for intraprocedural complications in MT. The colossus macrowire is easy to torque allowing for easy advancement.

• C. Inquiry into ADAPT success with the MINT technique:

In all cases, successful cases of MINT (n = 46/50), five cases required the use of the adjunctive device (n = 5/46) in the form of stent retrievers. Three different types of stent retrievers were used and included Solitaire X, Trevo NXT, and Embotrap. MINT, which still is an adaptation of ADAPT, was successful in 89% (n = 41/46) cases to achieve a successful recanalization (TICI ≥ 2b). In a few participating centers the standard is to use a bailout after two passes of aspiration technique have failed. There was one case where stent-retriever use was necessitated in view of underlying intracranial atherosclerosis. Although not truly a measure of the success of the MINT technique, the modified FPE (first pass effect) was 71% in this initial experience and relates to multiple factors that include the underlying etiology, catheter size, and clot characteristics. The first pass effect was 54% in this technique. In all four cases where MINT failed, adjunctive devices had to be utilized.

There are several limitations to our study. First, this is an observational study and is therefore prone to selection bias. In addition, the sample size was relatively small, and angiographic outcomes were operator adjudicated. Follow-up on a few patients was lost as they were transported to the comprehensive stroke center from a faraway location and did not return for follow-up there, many of these patients had already had significant improvement to be discharged to acute rehab or home. We plan to continue our work on this subject with an already planned large study, MINT Registry ⁷ with ADAPT and SOLUMBRA technique control arms. We also plan to analyze the cost-effectiveness of this technique in the near future.

Conclusions

Macrowire for Intracranial Thrombectomy (MINT) is safe and feasible for large vessel occlusion recanalization based on our initial clinical experience in this multicenter study.

Indiana University Institutional Review Board approval: 19347. Every center had an Institutional Review Board and data-sharing agreement with Indiana University or through data-sharing contracts executed through the Medical University of South Carolina (MUSC) (IRB:Pro00090704) STAR registry network.

Part of this study was presented as an oral presentation at the Society of NeuroInterventional Surgery (SNIS)-2024 meeting, in Colorado Springs, Colorado, USA.

Supplemental Material

Video 1. Complete fluoroscopy video of the technique