Endovascular Treatment Decisions in Patients with M2 Segment MCA Occlusions

DISCUSSION

EVT decision-making for patients with an acute ischemic stroke and M2 segment MCA occlusions has been subject to debate because these patients were generally excluded from the largest EVT trials. In our study, most of the physicians who participated in this survey reported that they favored EVT in patients with acute ischemic stroke with M2 segment MCA occlusion. This reflects confidence in EVT as a safe and effective treatment option, even beyond large-vessel occlusions. The small but significant gap between current and ideal treatment decisions indicates that, although the respondents believed that EVT should be performed, their environment did not yet allow them to do so. This might change in the future as more evidence for safety and efficacy of EVT in M2 segment MCA occlusions becomes available.^{4,7⇓⇓⇓-11}

Survey respondents were more likely to predict that they would treat patients with ICA–M1 segment MCA occlusions with EVT than patients with M2 segment MCA occlusions. This most likely reflects current guidelines, which assign Class-1 Level-A evidence for EVT only in proximal (ICA–M1 segment MCA) occlusions.⁶ Analyses of the influence of baseline characteristics on physicians’ decision to offer EVT to patients with M2 segment MCA occlusions revealed that the time from symptom onset to treatment, the baseline NIHSS, and the baseline ASPECTS were significant. This confirms that clinical and imaging baseline characteristics play an important role in clinical decision-making; the same variables that determine EVT eligibility in proximal-vessel occlusions⁶ are the variables that physicians rely on for decision-making in patients with M2 segment MCA occlusions.

Neither current nor ideal treatment decisions differed between academic and nonacademic centers in this survey. Physicians’ treatment decisions, therefore, do not seem to be influenced by their institution’s academic profile. Physicians who favor EVT under current local resources and under assumed ideal conditions worked in high EVT volume centers and performed significantly more EVT cases per year than those refraining from EVT. This reflects that experience with endovascular treatment makes physicians more comfortable offering EVT to their patients with M2 segment MCA occlusions. Interestingly, physicians who opt to use EVT in patients with M2 segment MCA occlusions were younger and had been in practice for fewer years than those who decided against using EVT. It is possible that these younger physicians were trained during the advent of stent retrievers and small distal aspiration catheters, techniques that make recanalization of M2 segment MCA occlusions safely achievable.

Significant differences were observed in reported EVT treatment decisions among the different geographic regions under current local resources but not under assumed ideal conditions (Fig 1B). Regions where physicians most preferred using EVT also showed the smallest gap between current and ideal treatment decisions, whereas regions with the lowest preference for using EVT showed the largest discrepancy between current and ideal decision rates. Respondents from Europe were less likely to offer EVT compared with the respondents from North America.

This could relate to access to EVT, differences in practice parameters and health care systems, differences in guidelines, and how practitioners implement these guidelines in their practice. Similarly, treatment decisions among different subspecialties under current local resources differed significantly but not under assumed ideal conditions (Fig 1C). These observations could point toward external factors (eg, insufficient access to treatment facilities, monetary and health policy–related limitations) as a possible cause for low EVT decision rates in some regions. For example, alteplase utilization remains <1% in many developing countries.¹³ This may motivate the use of EVT in regions where patients or local jurisdictions are unable to afford alteplase.¹⁴ The gap between current and ideal practices in such regions may also reflect the limited resources of publicly funded hospitals or the patients’ means in areas with mostly private hospitals. This could promote the use of manual aspiration at the clot interface as the primary and economically efficient EVT technique in local practices.¹³ In some other countries in Africa, Asia, and Europe, EVT is either not available or not offered around the clock.¹⁵ Such limitations with the subsequent impact on the access to EVT-capable facilities and devices are all important determinants of the decision for or against using EVT.

Although this study clearly shows that M2 segment MCA occlusions are considered an appropriate target for EVT across all countries and specialties, there was substantial variability in decision-making among physicians. This is not surprising because no randomized controlled trials demonstrated EVT efficacy in M2 segment MCA occlusions. To the best of our knowledge, there currently are no plans for such a trial. The main reason for this is the lack of clinical equipoise. Most physicians consider EVT the superior treatment for patients with all endovascular accessible occlusions, including the M2 segment; hence, only a few are willing to randomize patients with distal accessible occlusions.

Any future trial that seeks to enroll patients with M2 segment MCA occlusions, therefore, will need to take into account the lack of equipoise and the potential for bias in trial enrollment (patients with unfavorable risk profiles who are unlikely to benefit from EVT are more likely to get enrolled). Evidence from high-quality patient-level meta-analysis such as from the Highly Effective Reperfusion evaluated in Multiple Endovascular Stroke trials Collaboration⁷ and from cohort studies that enrolled patients with M2 segment MCA occlusions who have not been offered EVT such as the Identifying New Approaches to Optimize Thrombus Characterization for Predicting Early Recanalization and Reperfusion With IV Alteplase and Other Treatments Using Serial CT Angiography (INTERRSeCT) study,¹⁶ and numerous other nonrandomized studies^4,8⇓-11 may show the best available data for efficacy of EVT in such occlusions. In this situation, professional organizations and guideline committees may consider revising the endovascular treatment recommendations for M2 segment MCA occlusions despite the lack of Level-1A evidence. This will stimulate further improvement in the design of devices and aspiration catheters specifically tailored for distal vessels.