MeVO session / Distal session

Mechanical Thrombectomy in MeVO and DVO

Up to 25% to 40% of acute ischemic strokes are caused by medium vessel occlusions (MeVO). To date, mechanical thrombectomy for primary MeVO, especially distal vessel occlusions (DVO), remains controversial, along with technical strategies and anesthesia methods.

Existing clinical and imaging assessment tools were not designed for medium and distal vessel occlusions. In terms of stroke screening scales, among BE-FAST, LAMS, PASS, FAST-ED, EMS RACE, 3-ISS, VAN, and NIHSS, only LAMS, FAST-ED, and VAN have acceptable diagnostic performance. Identifying the culprit vessel and occlusion stump in MeVO and DVO is not as straightforward as in large vessel occlusions (LVO). Even with the aid of artificial intelligence, relying solely on CTA images, MeVO tend to be under-diagnosed. In such cases, wedge-shaped hypoperfusion areas shown on CTP images and 3D DSA imaging during procedure may provide additional information.

Patient selection for endovascular therapy (EVT) primarily relies on the mismatch between clinical symptoms and infarct core, as well as the presence of a salvageable penumbra. For instance, the ESCAPE-MeVO study enrolled patients with NIHSS > 5 or NIHSS 3–5 with disabling functional deficits. Randomized controlled trials (RCTs) comparing EVT with medical therapy, such as DISCOUNT, DISTAL, DISTALS, DUSK, ESCAPE-MeVO, FRONTIER-AP, and ORIENTAL-MeVO, predominantly included middle vessel occlusions (MeVO) and distal vessel occlusions (DVO) in vessels with diameters of 1.5–2.0–2.5 mm, such as M2–M4, A1–A3, and P1–P3. Regrettably, the results of the DISTAL, DISCOUNT, and RESCUE-MeVO studies, which were first presented at the 2025 International Stroke Conference, were all negative.  This may be related to lower revascularization rates and higher risks of symptomatic intracranial hemorrhage, among other technical and safety metrics. And MeVO demonstrate a more favorable response to intravenous thrombolysis compared to LVO. A pooled analysis of the aforementioned RCTs will provide higher-level evidence and help identify MeVO and DVO patients who may benefit from EVT.

From a technical standpoint, thrombectomy for MeVO and DVO requires greater consideration of safety. Maintaining the base catheter distal enough, striving for first pass effect, minimizing procedural complications, specifically vascular traction, displacement and injury, are crucial. In the stent retriever group, the number of attempts is the main factor associated with good prognosis and hemorrhagic complications, while in the aspiration group, it is mainly related to procedural time. Thrombectomy within three attempts, recanalization within one hour, and bridging thrombectomy are predictive of good outcomes. The risk of vascular perforation during MeVO thrombectomy is higher than that in LVO, mainly occurring during the steps of navigation the occlusion site and retrieval of the stent/aspiration catheter. This is especially true for tortuous and angulated DVOs such as A3, M3, P3, and superior cerebellar artery. The micro-ADAPT technique using a 0.027-inch microcatheter and a 4-5F intermediate catheters for dual aspiration may offer higher safety. Aspiration catheters with a beveled tip, such as ZOOM, have better trackability, or Tenzing Assisted Delivery of Aspiration (TADA) technique, could reach the clot without coaxial microwire and microcatheter navigating beyond the occlusion blindly.

Considering high heterogeneity in MeVO and DVO, firstline strategies can hardly be standardized. The aspiration force and efficacy is greatly rely on the match diameter between the aspiration catheter and the target vessel. For example, the 3MAX catheter with an outer diameter of 0.059 inch (1.5 mm) is comparable to the diameter of DVO vessels. Similarly, the diameter of the stent retriever should be compatible with the target vessel, i.e., tigertriever stent with adjustable diameter. The pRESET LITE stent (Phenox, Bochum, Germany), with its helical slit, closed ring and dual cell type design and sizes ranging from 3-20 to 4-20, combined with a 2-meter pusher wire, can maintain an open and configuration and well wall apposition in small vessels. In distal arteries, partial deployment techniques for thrombectomy stents, such as SPORNS, are often used to reduce vascular wall injury. For example, the ONE-SEG technique deploys only one segment of the Embotrap III stent retriever outside the microcatheter, making it more suitable for vessels with a diameter of 2 mm, applied in combined aspiration techniques like Solumbra with an intermediate catheter for contact aspiration.

In patients with failed thrombectomy or residual stenosis of more than 50%, the SAIL technique (stent retriever-assisted local tirofiban thrombolysis) can be considered before angioplasty. Distal arteries are more prone to vasospasm, and subsequent early reocclusion can be differentiated by administering vasodilators such as nimodipine intraarterially. The hypovascularity in capillary phase viewed on microcatheter angiography, especially in the inferior trunk of middle cerebral artery, may have compensation from the leptomeningeal branches of the anterior and posterior cerebral arteries. It is not necessary to overly pursue perfect recanalization results. Over-treatment can be counterproductive; patients with failed thrombectomy may have even worse outcomes than those treated with medical therapy, likely attributed to excessive attempts and symptomatic intracranial hemorrhage complications .

Reference

1. Tonetti DA, Koneru M, Bhattacharyya M, English JD, Settecase F, Kim WT, Khalife J, Patel P, Thomas A, Jovin T, Hanel R, Benalia VHC, Cortez GM, Aghaebrahim A, Sauvageau E, Abdalkader M, Nguyen TN, Klein P, Dmytriw AA, Shaikh H. Tenzing 7 delivery catheter with or without a leading microwire for single pass aspiration thrombectomy: A multicenter experience. Interv Neuroradiol. 2023 Nov 28:15910199231216765. doi: 10.1177/15910199231216765.
2. Tanaka Y, Watanabe D, Kanoko Y, Inoue A, Kato D, Igasaki S, Kikuta A, Ogasawara M, Kanemaru K, Maruoka H. Optimizing thrombectomy in medium vessel occlusion: Focus on vessel diameter. Interv Neuroradiol. 2024 Aug 8:15910199241272638. doi: 10.1177/15910199241272638.
3. Ospel JM, Nguyen TN, Jadhav AP, Psychogios MN, Clarençon F, Yan B, Goyal M. Endovascular Treatment of Medium Vessel Occlusion Stroke. Stroke. 2024 Mar;55(3):769-778. doi: 10.1161/STROKEAHA.123.036942.
4. Wang M, et al; M.A.D.-M.T. Consortium. Use of the pRESET LITE thrombectomy device in combined approach for medium vessel occlusions: A multicenter evaluation. Neuroradiology. 2024 Apr;66(4):631-641. doi: 10.1007/s00234-024-03302-5.
5. Ospel JM, Dowlatshahi D, Demchuk A, Volders D, Möhlenbruch M, Nimjee S, Kennedy J, Buck B, Shankar JJ, Booth TC, Jumaa MA, Fahed R, Ganesh A, Zhang Q, Doram C, Ryckborst KJ, Hill MD, Goyal M; ESCAPE-MeVO investigators. Endovascular treatment to improve outcomes for medium vessel occlusions: The ESCAPE-MeVO trial. Int J Stroke. 2024 Oct;19(9):1064-1070. doi: 10.1177/17474930241262642.
6. Schulze-Zachau V, et al. Incidence and outcome of perforations during medium vessel occlusion compared with large vessel occlusion thrombectomy. J Neurointerv Surg. 2024 Jul 16;16(8):775-780. doi: 10.1136/jnis-2023-020531.
7. Sriwastwa A, Aziz YN, Weiss K, Buse R, Zhang B, Demel SL, Ali A, Voleti S, Wang LL, Vagal AS. Performance of An Automated Algorithm in Large and Medium Vessel Occlusion Detection: A Real-World Experience. AJNR Am J Neuroradiol. 2024 Sep 26:ajnr.A8509. doi: 10.3174/ajnr.A8509.
8. Ali A, Rao R, Sharkey B, Gega A, Oliver M, Chen T, Burgess R, Jumaa M, Zaidi S. Medium vessel occlusion thrombectomy: Single center experience using the 3 MAX catheter. Interv Neuroradiol. 2024 Jul 25:15910199241264328. doi: 10.1177/15910199241264328.
9. Faizy TD, et al; MAD-MT Investigators. Clinical outcomes of patients with unsuccessful mechanical thrombectomy versus best medical management of medium vessel occlusion stroke in the middle cerebral artery territory. J Neurointerv Surg. 2025 Jan 23:jnis-2024-022642. doi: 10.1136/jnis-2024-022642.
10. Radu RA, et al; MAD-MT Consortium. Outcomes with General Anesthesia Compared to Conscious Sedation for Endovascular Treatment of Medium Vessel Occlusions: Results of an International Multicentric Study. Clin Neuroradiol. 2024 Dec;34(4):761-769. doi: 10.1007/s00062-024-01415-1.
11. Settecase F, et al. Tenzing Assisted Delivery of Aspiration (TADA) technique for thrombectomy of medium vessel occlusions using the Freeclimb 54 catheter: multicenter experience. J Neurointerv Surg. 2025 Jan 23:jnis-2024-022693. doi: 10.1136/jnis-2024-022693.
12. Kothari SA, et al Comparing validated stroke screening scales for identifying large and medium vessel occlusions: a prospective observational cohort study. J Neurointerv Surg. 2025 Jan 27:jnis-2024-022309. doi: 10.1136/jnis-2024-022309.
13. Radu RA, et al. First pass effect as an independent predictor of functional outcomes in medium vessel occlusions: An analysis of an international multicenter study. Eur Stroke J. 2024 Mar;9(1):114-123. doi: 10.1177/23969873231208276.
14. Alawieh AM, et al; STAR Collaborators. Multicenter investigation of technical and clinical outcomes after thrombectomy for distal vessel occlusion by frontline technique. J Neurointerv Surg. 2023 Sep;15(e1):e93-e101. doi: 10.1136/jnis-2022-019023.
15. Anastasiou A, et al. Rescue therapy after failed thrombectomy in medium/distal vessel occlusions: A retrospective analysis of an international, multi-center registry. Eur Stroke J. 2025 Jan 4:23969873241311152. doi: 10.1177/23969873241311152. Epub ahead of print. PMID: 39754521; PMCID: PMC11700384.
16. Rodrigo-Gisbert M, et al. Stent Retriever AssIsted Lysis Technique with Tirofiban: A Potential Bailout Alternative to Angioplasty and Stenting. AJNR Am J Neuroradiol. 2024 Nov 7;45(11):1701-1707. doi: 10.3174/ajnr.A8374.
17. Goyal M, et al; ESCAPE-MeVO Investigators. Endovascular Treatment of Stroke Due to Medium-Vessel Occlusion. N Engl J Med. 2025 Feb 5. doi: 10.1056/NEJMoa2411668.
18. Psychogios M, et al; DISTAL Investigators. Endovascular Treatment for Stroke Due to Occlusion of Medium or Distal Vessels. N Engl J Med. 2025 Feb 5. doi: 10.1056/NEJMoa2408954.