Setareh Salehi Omran, MD
Endovascular thrombectomy (ET) is an established treatment for cerebral large vessel occlusions. However, the role of ET in medium vessel occlusions (MeVO) is less clear. MeVO involve the smaller caliber arteries branching from the larger cerebral vessels; namely, the M2 and M3 of the middle cerebral artery, A2 and A3 of the anterior cerebral artery, and P2 and P3 of the posterior cerebral artery. Patients with MeVO were mostly excluded from the large landmark ET trials, perhaps due to the greater technical difficulty of retrieving clots in smaller vessels, and the perceived lower burden of disability and higher rate of successful recanalization with intravenous alteplase. However, studies have shown mixed findings on the degree of recanalization and overall outcome after a MeVO. Therefore, examining the clinical course of acute ischemic strokes from MeVO may provide further evidence supporting the need for considering ET.
Ospel et al1 examined the clinical course of MeVO with and without intravenous alteplase using prospectively collected data from INTERRSeCT (The Identifying New Approaches to Optimize Thrombus Characterization for Predicting Early Recanalization and Reperfusion With IV Alteplase and Other Treatments Using Serial CT Angiography) and PRoveIT (Precise and Rapid Assessment of Collaterals Using Multi-Phase CTA in the Triage of Patients With Acute Ischemic Stroke for IA Therapy). Both cohort studies include patients presenting with acute ischemic stroke with a baseline CTA within 12 hours of their last known normal. Patients with a confirmed MeVO on their baseline CTA who did not undergo ET were included in the analysis. The prespecified primary outcome was excellent clinical outcome with modified Rankin Scale (mRS) 0-1, and the secondary outcomes were ordinal mRS score and good functional outcome with mRS 0-2 at 90 days. Outcomes were compared between patients who did and did not receive intravenous alteplase, and between patients with and without successful recanalization on follow-up CTA (TICI 2b or 3).
A total of 258 patients were included in the analysis; more than half had an occlusion within the M2 branch of their middle cerebral artery. The majority of patients (72%) received intravenous alteplase. Patients receiving intravenous alteplase had higher baseline NIHSS, shorter onset to imaging time, and shorter imaging to repeat imaging time. Among the entire cohort, 50% of patients achieved an excellent outcome and 67% achieved a good functional outcome at 90 days. In adjusted analysis, intravenous alteplase was associated with ordinal mRS (adjusted common odds ratio [OR], 0.55, 95% CI 0.33 – 0.92), but not with excellent or good clinical outcome. Of the 201 (78%) patients who had follow-up CTA imaging available, early recanalization was achieved in 42% of patients. Patients who received intravenous alteplase were more than twice as likely to achieve early recanalization compared to those who did not receive intravenous alteplase (47% versus 21%). Early recanalization was associated with excellent outcome (adjusted OR, 2.29, 95% CI 1.0-4.4) and ordinal mRS (adjusted common OR, 0.6, 95% CI 0.3-1.0). Overall, the study showed that half of patients with MeVO achieved an excellent functional outcome, and that 42% of patients achieved early recanalization with current standard of care.
This study has several strengths, including its use of prospectively collected data, independently verified CTA images, and availability of follow up CTA imaging on the majority of the patients. There are several noteworthy limitations. The majority of included patients received intravenous alteplase, and the reason for not administering intravenous alteplase was not specified. It is possible that patients who did not receive intravenous thrombolysis had other medical comorbidities that may have affected their outcome. Additionally, most cases were due to an M2 vessel occlusion, and only 15% of cases involved MeVO of the anterior or posterior cerebral arteries. It is also unclear whether the affected M2 arteries were dominant, non-dominant, or co-dominant, which may affect the NIHSS and the clinical outcome.
Despite these limitations, the findings provide valuable information that can guide future studies on the role of ET in MeVO. The limited available data from MR CLEAN and meta-analyses favor ET in M2 vessel occlusions, particularly in patients with a dominant M2.2-4 There is a lack of data on the safety of ET in MeVO of the anterior and posterior cerebral arteries. Given that only half of patients achieved an excellent functional outcome and less than half had early recanalization, future randomized studies should explore the benefit of ET in patients with MeVO.
References:
1. Ospel JM, Menon BK, Demchuk AM, Almekhlafi MA, Kashani N, Mayank A, et al. Clinical course of acute ischemic stroke due to medium vessel occlusion with and without intravenous alteplase treatment. Stroke. 2020;51:3232-3240
2. Compagne KCJ, Sluijs PMvd, Wijngaard IRvd, Roozenbeek B, Mulder MJHL, Zwam WHv, et al. Endovascular treatment. Stroke. 2019;50:419-427
3. Saber H, Narayanan S, Palla M, Saver JL, Nogueira RG, Yoo AJ, et al. Mechanical thrombectomy for acute ischemic stroke with occlusion of the m2 segment of the middle cerebral artery: A meta-analysis. J Neurointerv Surg. 2018;10:620-624
4. Menon BK, Hill MD, Davalos A, Roos YBWEM, Campbell BCV, Dippel DWJ, et al. Efficacy of endovascular thrombectomy in patients with m2 segment middle cerebral artery occlusions: Meta-analysis of data from the hermes collaboration. Journal of NeuroInterventional Surgery. 2019;11:1065-1069
