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Abstract
Background Mechanical thrombectomy using stentrievers is the standard of care for emergent large vessel occlusion stroke. Data on the use of stentrievers in smaller caliber vessels are sparse.
Objective To present our initial experience with the Mindframe Capture LP device, which was designed for mechanical thrombectomy in small cerebral arteries.
Methods A retrospective chart review was conducted of patients who underwent Mindframe device assisted emergent thrombectomy. Clinical, imaging, procedural and early follow-up data were obtained.
Results Nine patients met inclusion criteria (5 men, median age 62 years). Median National Institute of Health Stroke Scale (NIHSS) score was 18 (IQR 9–22), and 6 patients received intravenous tissue plasminogen activator. Six patients had M2 segment occlusions, and 2 patients had distal M1 segment occlusions of the middle cerebral artery. One had distal basilar artery occlusion. Median vessel diameter at the thrombus was 1.7 mm (IQR 1.5–2.5). In all 9 patients the Mindframe device was used together with manual aspiration, with median groin puncture to recanalization time of 35 min (IQR 27–54), and median procedural time of 67 min (IQR 51–91). Final Thrombolysis in Cerebral Infarction score was 3 and 2b in 4 patients each (89% total), and 2a in 1 patient. No patient had any postprocedural complications or symptomatic intracerebral hemorrhage. Median postprocedure and discharge NIHSS were 4 and 1, respectively.
Conclusions Our data suggest that the Mindframe device is safe and effective for rapid treatment of acute strokes involving small caliber intracranial vessels. Further study in a larger cohort is warranted.
- Thrombectomy
- Stroke
- Technology
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Introduction
Mechanical thrombectomy using stent retrievers for emergent large vessel occlusion (ELVO) stroke has become the standard of care.1 Together with improvements in systems of care and triaging of patients with ELVO for mechanical thrombectomy, advances in endovascular devices and techniques will also be necessary, especially to improve the rates of recanalization. Data for mechanical thrombectomy in more distal or smaller caliber cerebral vessels are scarce, despite the fact that they have been shown to be associated with poor outcomes.2 ,3 The prevalence of distal ELVO strokes in recent positive randomized endovascular trials has varied from 2 to 14%.4–8 There has been a general concern that performing mechanical thrombectomy in patients with acute stroke with distal or smaller caliber vessel occlusion may carry a higher risk than benefit.9–11 However, a small number of non-randomized studies examining endovascular therapy for distal ELVO have shown beneficial outcomes with mechanical thrombectomy.9 ,10 ,12 The Mindframe Capture LP revascularization device (Medtronic, Minneapolis, Minnesota, USA) was approved in 2012 in Europe for ELVO in smaller vessels. In the USA, the Food and Drug Administration (FDA) has only recently approved it.13 We are one of the first centers in the USA to present our experience using this new stent retriever device.
Methods
After approval from the institutional review board, we retrospectively reviewed patients who underwent endovascular therapy for distal ELVO strokes between January and August 2015. We collected data on clinical characteristics, imaging, procedural variables, and follow-up data. Procedural variables included groin puncture time, first pass time, number of passes, recanalization time, Thrombolysis in Cerebral Infarction (TICI) score, and procedural complications.14 Clinical outcomes were defined using the National Health Institute Stroke Scale (NIHSS). Hemorrhagic transformation on postprocedure imaging was classified according to the European Cooperative Acute Stroke Study (ECASS) II classification, while symptomatic hemorrhage was defined according to ECASS III classification.15
Device
The Mindframe Capture LP (Medtronic, Minneapolis, Minnesota, USA) is a mechanical revascularization device approved by the FDA for restoring blood flow in patients with acute ischemic stroke due to intracranial large vessel occlusion within 8 h of symptom onset. The device is a laser-cut stent made of nitinol attached to a nitinol push wire (figure 1). It has one platinum–iridium and two platinum–tungsten radiopaque markers on the proximal and distal ends, respectively. It comes in four sizes: 3×20 mm, 3×30 mm, 4×20 mm and 4×30 mm, with a usable length of 15 mm and 23 mm for the 20 mm and 30 mm stents, respectively. The minimum microcatheter inner diameter is 0.0165 inch, and the recommended vessel diameter ranges from 2.0 mm to 3.5 mm.16 The above characteristics and overall smaller dimensions relative to other ELVO embolectomy devices, such as Trevo (Stryker Neurovascular, Fremont, California, USA) and Solitaire (Medtronic, Minneapolis, Minnesota, USA), make this stentriever a favorable candidate for distal and/or smaller caliber cerebral vessels.
(A) Mindframe Capture LP device with attached thrombus from case 7. (B) Mindframe Capture LP device.
Technique
We used a tri-coaxial system for most cases with a generic 6F Shuttle guide sheath, 5F or 6F intermediate catheters and a 0.0165 or 0.017 microcatheter. Under roadmap guidance, the microcatheter was advanced over a microwire to traverse the clot. Then the Mindframe Capture LP device was advanced to the microcatheter tip, and systematically unsheathed into the clot. The stent was allowed to expand over 4–5 min. An injection through the guide confirmed adequate stent placement, and often showed temporary reperfusion. The stent was then gently pulled back into the intermediate catheter with concurrent manual aspiration with a 60 mL syringe. The device was examined for clot fragments, and a repeat angiographic run was performed to establish patency of the vessel. If the vessel remained partially or completely occluded, the device was resheathed, and the process was repeated.
Results
We identified nine patients who underwent mechanical thrombectomy with the Mindframe Capture LP device (table 1); five were men (56%) with a median age of 62 years (IQR 55–63). Location of the ELVO was as follows: distal basilar occlusion—one patient, distal M1 segment of the middle cerebral artery (MCA)— two patients, and M2 segment of the MCA—six patients. Median initial NIHSS was 18 (IQR 9–22), and median Alberta Stroke Program Early CT (ASPECT) score was 8. Six patients received IV tissue plasminogen activator (tPA). The Mindframe Capture LP device was the stent retriever primarily used in five patients. One patient received IA tPA, a Solitaire 2FR stent retriever was used in two patients, and in one patient a direct aspiration first-pass (ADAPT) technique17 was used before application of the Mindframe Capture LP device. One patient had an ELVO stroke during an aneurysm coil embolization procedure (Patient #6); as thus preprocedure imaging and procedural times of this patient were not included in the final analysis. Median time from ‘last known well’ to groin puncture was 284 min (IQR 240–332), median groin puncture to recanalization time was 35 min (IQR 27–54), and median procedural time (groin puncture to end of the case) was 67 min (IQR 51–91). Median vessel luminal diameter at the site of occlusion was 1.7 mm (IQR 1.5–2.5), and average vessel diameter was 2.0 mm. Final TICI score was 2b and 3 in four patients each (44% each) with a combined TICI 2b–3 score present in 89%, and 2a in 11% of cases (figure 2). Seven patients (78%) required only a single pass with the Mindframe Capture LP device. Median postprocedure NIHSS score was 4 (IQR 2–6) while median discharge NIHSS score was 1 (IQR 0–2). No patient had any device-related complication during the procedure. No patients had any symptomatic intracerebral hemorrhage, while one patient (11%) had an HI-1 hemorrhagic transformation on postprocedure imaging. Six patients (67%) were discharged directly to home.
Procedure and patient characteristics
Case 7. (A) Initial angiogram run showing M2 segment of the middle cerebral artery occlusion (arrow). (B) Angiogram native image showing Mindframe Capture LP device in situ (black arrow) with distal markers (white arrow). (C) Final angiogram run demonstrating successful recanalization of the previously occluded vessel (arrow).
Discussion
In our initial experience, the Mindframe Capture LP device was safe and efficient, with excellent recanalization rates. We had a TICI 2b–3 score in almost 90% of patients, achieved with a single pass in the majority of cases. Importantly, this device was successfully used in small caliber vasculature: almost 90% of our patients had an arterial diameter of ≤2.5 mm, with an average size of 2.0 mm. Recanalization was achieved rapidly, at a median of 35 min. We did not identify any device-related periprocedural complications, or any postprocedural symptomatic hemorrhage. Early clinical outcomes data (up to discharge) suggested a dramatic improvement in NIHSS scores, and two-thirds of the patients were able to return home directly from the hospital.
Neurointerventionalists often try to avoid attempts to recanalize distal ELVO, because a relatively smaller brain territory is considered at risk, and tortuosity and size of the distal vessels make the procedure technically challenging.9 ,10 However, according to a few previous reports, up to 60–75% of untreated distal ELVO strokes may be associated with poor outcome, with mortality rates being as high as 24%.2 ,3 The recently published positive endovascular stroke trials did have a small number of patients with involvement of the M2 MCA segment.4–8 However, safety and outcomes in this specific subgroup are difficult to decipher owing to the small sample size. In the earlier Prolyse in Acute Cerebral Thromboembolism (PROACT) II trial, a subgroup analysis of M2 occlusions showed a threefold increase in recanalization, and a twofold increase in functional independence at 90-days compared with controls.18 In the subgroup analysis of the Interventional Management of Stroke trial II (IMS II), around 70% patients with M2 occlusions achieved favorable outcomes.19 In addition, retrospective single-arm studies examining M2 segment ELVO stroke and mechanical thrombectomy have shown that recanalization rates with M2 segments were higher than those with M1, and these patients had better outcomes.9 ,10
However, vessel tortuosity has always been a challenge, and tortuous vessels may be a cause of poor recanalization.20 Although several endovascular trials using stent retrievers have been shown to have a favorable safety record,4–8 Schwaiger et al21 recently showed that the pREset stent retriever (Phenox GmbH, Bochum, Germany), approved in Europe for ELVO stroke, had lower recanalization rates if used in tortuous vessels.
The overall small caliber of treated vessels has also been a significant concern when treating patients with acute stroke with distal vessel occlusion. There is a reasonable concern that smaller diameter vessels or adjacent perforators may be more susceptible to injury, especially when traction is applied with a stentriever. Fortunately, we did not encounter this potential problem, even though almost all of our patients had a vessel caliber ≤2.5 mm.
Our findings are comparable to those of a recent study using a smaller stent retriever, the Trevo XP ProVue 3×20 mm or ‘Baby Trevo’ (Stryker Neurovascular, Fremont, California, USA), which has also shown promising results in eight treated patients, even in distal and tortuous vessels.12
Limitations of our study include retrospective review, relatively small number of patients, and single-center experience. To our knowledge, this is the first report on the use of the Mindframe Capture LP device for recanalization of small diameter cerebral vessels in patients with acute stroke.
Conclusion
Our single-center initial experience with the Mindframe LP has shown that the device can be safely, rapidly, and efficiently used for the treatment of acute stroke caused by occlusion of a small caliber cerebral vessel. Further study in a larger cohort is warranted.
References
Footnotes
Contributors RC: design of the work, acquisition of data, interpretation of data, drafting of the manuscript. GT: study conception and design, acquisition of data, interpretation of data, critical revision of the manuscript. FH: study conception, interpretation of data, critical revision of manuscript. All authors assisted in interpretation of data and critical revision of manuscript.
Competing interests PR is on the scientific advisory board for Medtronic Neurovascular and Stryker Neurovascular.
Ethics approval Institutional review board.
Provenance and peer review Not commissioned; externally peer reviewed.