Major randomized clinical trials have established the superiority of mechanical thrombectomy (MT) to medical management in patients with acute ischemic stroke due to large vessel occlusion of the anterior circulation (1–7). Newer generation MT devices have allowed operators to navigate more distally and with higher technical precision, expanding the potential therapeutic applications of MT. Yet, current evidence supporting the safety and efficacy of MT for distal occlusion is limited given the exclusion of these patients in major clinical trials. A recent meta-analysis of patients with occlusion of the M2 segment of the middle cerebral artery (MCA) demonstrated a benefit of MT over best medical care for 90-day modified Rankin Scale (mRS) score, but other apparent benefits were not statistically significant (8). M2 occlusions have also been associated with a higher rate of revascularization after treatment with intravenous tissue plasminogen activator (rTPA) compared to more proximal occlusions (9). Accordingly, available international guidelines do not recommend MT for distal occlusions based on the current level of scientific evidence (10).

The CatchView Mini (CVM; Balt, Montmorency, France) is a new version of the low-profile, laser-cut nitinol Catch+ Mini (Balt, Montmorency, France) stent retriever (SR) that boasts improved visibility and device length, as well as an overlapping structure that yields good adaptability to arterial conformation with less rectification during the clot extraction. The aim of this research was to examine the safety and efficacy of MT for occlusions of the M2 or more distal segments of the MCA. We investigated clinical, radiologic, and safety outcomes after MT with the CVM device.

Patient baseline characteristics are described in Table 1 and study outcomes are presented in Table 2.

In the present study, a majority of patients treated with the CVM device for an M2 occlusion achieved successful reperfusion (TICI 2b/3). MT was also associated with a low risk of complications and a 90-day mortality rate consistent with those reported in previous clinical trials. Taken together, our findings support the safety and efficacy of MT with the CVM for distal occlusion of the MCA.

The rate of successful recanalization in this study was notably higher than that reported after intravenous alteplase in a study of patients with M2 segment MCA occlusions (37.1%) (13) and in the HERMES meta-analysis (59.2%) (8). A high rate of reperfusion in the present study may be in part attributable to our treatment protocol, which implements a proximal balloon guiding catheter together with a new-generation, long (20 mm), low-profile ST that offers better flexibility, adaptability, and navigability for treating small and tortuous vessel occlusions than STs typically used to treat proximal occlusions. Previous research suggests that ST length influences recanalization success (14). Moreover, the CVM is fully compatible with the low-profile Headway Duo microcatheter (1.3F distally, 0.012″ internal lumen), which has been previously demonstrated to reduce the likelihood of clot migration during MT (15).

We similarly observed good clinical outcomes in our study, with more than half patients exhibiting functional independence (mRS 0–2) at 90 days post-procedure. In the HERMES meta-analysis, the direction of clinical benefit generally favored endovascular treatment over medical treatment (mRS 0–2 at 90 days 58.2 vs. 39.7%, respectively), but the results were not statistically significant for all outcomes (8). A larger benefit observed in our study may be due to differences between studies in the included patient population and the use of different treatment protocols, as the HERMES analysis included a broad variety of intra-arterial therapies. Moreover, the meta-analysis results may have been underpowered given the small, pooled sample size of patients with M2 occlusion. Finally, divergence between our results and those of the meta-analysis may have been related to differing definitions as to what constitutes M1 occlusion vs. M2 occlusion from an anatomical perspective (9).

MT with the CVM in our study produced a low rate of complications. There were no observed cases of SICH and relatively few cases of subarachnoid hemorrhage and type-1 intraparenchymal hemorrhage. Additionally, there were no cases of vessel perforation or extravasation. These results are consistent with those reported by the HERMES meta-analysis, which did not identify any SICH or major procedural complications in the endovascular treatment group vs. a cumulative rate of 7.9% in the control arm (8). In contrast, a meta-analysis by Saber et al. (16) reported a 10% rate of SICH after MT for distal occlusion. A higher rate of SICH in the aforementioned study may reflect the risk associated with the use of devices designed for proximal occlusion to treat smaller or more fragile vessels. Furthermore, Baharvahdat et al. (17) examined the rates of post-thrombectomy subarachnoid hemorrhage based on occlusion location and described a higher rate in the M2 group compared to the M1 group (25 vs. 12%; P = 0.010); however, this difference was not associated with significant long-term clinical consequences. In our series, we detected a lower rate of subarachnoid hemorrhage with no observed worsening of the patients' clinical condition.

MT in our study was not associated with vessel vasospasm in any patient. Vessel vasospasm was detected in a significant number of patients (22.5%) who underwent treatment with a ST in the SWIFT trial (18) and in more than half of the patients in the Baby Trevo series (19) without clinical sequelae, which may indicate that this is not a hazardous event. Nonetheless, intra-arterial vasodilator infusion either prophylactically or to treat angiographic vasospasm produced good results in these studies. Finally, it is noteworthy that the 90-day mortality rate observed in our study is comparable to that reported in previous trials [11.9% (8) and 15.8% (16)].

The present study has several limitations. First, we included a relatively small sample size. Given a paucity of corroborating evidence for the safety and efficacy of our treatment protocol, additional data is necessary to support MT as a therapeutic option for distal MCA occlusion in international guidelines. Second, the present research was a prospective case series and, therefore, lacked randomization and a control arm for comparison. It is important to acknowledge that a careful risk benefit assessment is important, especially in a context of distal occlusion. Future efforts should include a randomized controlled trial of MT vs. medical therapy for M2 occlusion; however, this may not be feasible due to the lack of clinical equipoise, as MT is now routinely performed for M2 occlusion in contrast with guideline recommendations. Finally, it is important to underscore that our study findings were likely bolstered by use of the CVM device, which offers key advantages for the treatment of distal occlusions relative to STs employed for the treatment of proximal occlusions.

Our analysis demonstrates that, in a context of distal M2 occlusion, MT with the CVM device is associated with a low risk profile and a high rate of recanalization success.

The raw data supporting the conclusions of this article will be made available by the authors, without undue reservation.

The studies involving human participants were reviewed and approved by Hospital Universitario Central de Asturias: Ethics Committee. The patients/participants provided their written informed consent to participate in this study.

PV: responsible for the integrity of the study, study design, data collection, analysis and interpretation of data, statistical treatment, literature research, text writing, critical revision, and approval of the final version. EM: critical revision, approval of the final version, and responsible for the integrity of the study. JJ and JC: text writing, data collection, study design, and approval of the final version. MG-D, LB, FG-A, and JP: critical revision and approval of the final version. All authors contributed to the article and approved the submitted version.

The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.

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