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Thrombectomy
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Mechanical thrombectomy, or simply thrombectomy, is the removal of a blood clot (thrombus) from a blood vessel, often and especially endovascularly as an interventional radiology procedure called endovascular thrombectomy (EVT). It thus contrasts with thrombolysis (clot dissolution) by thrombolytic medications (e.g., alteplase, reteplase), as either alternative or complement thereto. It is commonly performed in the cerebral arteries (interventional neuroradiology) as treatment to reverse the ischemia in some ischemic strokes (i.e., those in which the blockage is a suitable candidate for such retrieval). Open vascular surgery versions of thrombectomy also exist. The effectiveness of thrombectomy for strokes was confirmed in several randomised clinical trials conducted at various medical centers throughout the United States, as reported in a seminal multistudy report in 2015.[1]
Applications in brain
[edit]Ischemic stroke represents the fifth most common cause of death in the western world and the number one cause of long-term disability. Until recent times, systemic intravenous fibrinolysis was the only evidence-based therapy for patients with acute onset of stroke due to large vessel occlusion.
History
[edit]The world's first thrombectomy (in case of blood clot in the brain) was performed in 1994 at Sahlgrenska University Hospital, Gothenburg, Sweden by senior physician Gunnar Wikholm.[2][3]
In 2015, the results of five trials from different countries were published in the New England Journal of Medicine, demonstrating the safety and efficacy of mechanical thrombectomy with stent-retrievers in improving outcomes and reducing mortality for patients who present within six hours from their time last known well. It is now a widespread procedure performed in many hospitals around the globe, especially comprehensive stroke centers, although many other hospitals are not yet able to supply the service enough to meet the need.[4] Large obstacles to making EVT more widely available are both systematic hurdles at the prehospital stages[4] and the intrahospital barrier of a scarcity of interventional neuroradiologists.[4][5] They concern TTR (time to reperfusion), which is the same underlying problem as the golden hour in general, albeit several hours in the case of TTR: that is, EVT performed within 2 or 3 hours can help vastly, whereas EVT performed after 6 to 12 hours is often (although not always) too late to prevent the permanent sequelae of the ischemia.[4] In this respect, the dissemination of EVT into clinical practice shows how translational medicine has various layers, some easier to solve and some harder: it was in some respects straightforward to develop the technology of EVT in the 2000s and 2010s (that is, the catheter tips and procedures),[4] but it is not easy to revamp the standard of care in prehospital settings (such as awareness among family members and bystanders, optimal techniques for emergency medical services, and so on),[4] which deployment of timely EVT requires.[4]
In 2018 the DAWN and DEFUSE-3 trials were published. These trials showed that mechanical thrombectomy is a safe and effective treatment for individuals who have an acute ischemic stroke, even (in some cases) out to 24 hours after symptom onset.[6][7] Most studies, however, have focused on thrombectomies in anterior circulation strokes. In recent years, increasing evidence on the efficacy of mechanical thrombectomy in posterior circulation strokes has been published.[8]
Stent-retriever thrombectomy
[edit]The procedure can be performed with general anesthesia or under conscious sedation in an angiographic room. A system of coaxial catheters is pushed inside the arterial circulation, usually through a percutaneous access to the right femoral artery. A microcatheter is finally positioned beyond the occluded segment and a stent-retriever is deployed to catch the thrombus; finally, the stent is pulled out from the artery, usually under continuous aspiration in the larger catheters.[citation needed]
Direct aspiration
[edit]A different technique for mechanical thrombectomy in the brain is direct aspiration. It is performed by pushing a large soft aspiration catheter into the occluded vessel and applying direct aspiration to retrieve the thrombus; it can be combined with the stent-retriever technique to achieve higher recanalization rates, but the complexity of the procedure increases.[citation needed]
Direct aspiration has not been studied as thoroughly as stent-retriever thrombectomy, but it is still widely performed because of its relative simplicity and low cost.[citation needed]
Delivery
[edit]Patients in London who suffered stroke were found to be much more likely to get thrombectomy in 2022 than those in other parts of England. 42% of thrombectomy units only operated during office hours and Monday to Friday, largely due to a shortage of neurointerventionalists.[5]
See also
[edit]References
[edit]- ^ Saver JL, Goyal M, Bonafe A, et al. (June 11, 2015). "Stent-Retriever Thrombectomy after Intravenous t-PA vs. t-PA Alone in Stroke" (PDF). New England Journal of Medicine. 372 (24): 2285–2295. doi:10.1056/NEJMoa1415061. PMID 25882376.
- ^ Wikholm G (May 1, 2003). "Transarterial Embolectomy in Acute Stroke". American Journal of Neuroradiology. 24 (5): 892–894.
- ^ Rentzos A, Wikholm G (October 2014). "Embolectomy for Acute Ischemic Stroke in the Anterior Cerebral Circulation: The Gothenburg Experience during 2000-2011". American Journal of Neuroradiology. 35 (10): 1936–1941. doi:10.3174/ajnr.A3997. PMC 7966239. PMID 24948503.
- ^ a b c d e f g Holland E (March 1, 2023). "This Revolutionary Stroke Treatment Will Save Millions of Lives. Eventually". The New York Times. Retrieved March 1, 2023.
- ^ a b Moore A (July 27, 2022). "Londoners several times more likely to get life-saving treatment". Health Service Journal. Retrieved September 28, 2022.
- ^ Albers GW, Marks MP, Kemp S, et al. (February 22, 2018). "Thrombectomy for Stroke at 6 to 16 Hours with Selection by Perfusion Imaging". New England Journal of Medicine. 378 (8): 708–718. doi:10.1056/NEJMoa1713973. PMC 6590673. PMID 29364767.
- ^ Nogueira RG, Jadhav AP, Haussen DC, et al. (January 4, 2018). "Thrombectomy 6 to 24 Hours after Stroke with a Mismatch between Deficit and Infarct". New England Journal of Medicine. 378 (1): 11–21. doi:10.1056/NEJMoa1706442. PMID 29129157.
- ^ Klail T, Piechowiak EI, Krug N, et al. (April 2024). "Endovascular revascularization of vertebrobasilar tandem occlusions in comparison to isolated basilar artery occlusions: A multi-center experience". Interventional Neuroradiology. doi:10.1177/15910199241240045. PMC 11571482. PMID 38576395.
External links
[edit]Thrombectomy
View on GrokipediaDefinition and Fundamentals
Procedure Description
Endovascular thrombectomy is a minimally invasive interventional procedure designed to mechanically remove thrombi obstructing cerebral arteries, primarily in cases of acute ischemic stroke caused by large vessel occlusion.[1] Performed under fluoroscopic imaging guidance in a catheterization laboratory, it involves percutaneous vascular access, typically via the common femoral artery in the groin, where a sheath is inserted to facilitate catheter introduction.[11] Local anesthesia with conscious sedation is standard, allowing real-time neurological assessment during the intervention.[1] The procedure commences with diagnostic cerebral angiography to confirm the occlusion site and extent, often following initial non-contrast CT or CT angiography for patient selection.[12] A guide catheter is advanced over a 0.035-inch guidewire to the proximal target vessel, such as the internal carotid or middle cerebral artery.[1] A smaller microcatheter (0.017–0.021 inch) and microwire (0.014–0.016 inch) are then navigated through the thrombus to a position distal to the occlusion, enabling precise device delivery.[12] Thrombus retrieval employs devices such as stent retrievers or aspiration catheters. In stent-retriever methods, the retriever (e.g., a self-expanding nitinol mesh like Solitaire) is deployed from the microcatheter, allowed to expand and integrate with the clot for 3–5 minutes, then withdrawn under continuous proximal aspiration via the guide catheter to minimize embolization.[12][1] Direct aspiration techniques position a large-bore catheter (e.g., 6–8 French) at the thrombus face and apply manual or pump-generated negative pressure to suction the material, often as a first-line or adjunctive approach (e.g., ADAPT: A Direct Aspiration First Pass Technique).[1] Multiple passes may be required, with post-retrieval angiography assessing reperfusion via the Thrombolysis in Cerebral Infarction (TICI) scale, targeting grades 2b–3 for near-complete or full flow restoration.[12] The intervention typically lasts 60–120 minutes, influenced by occlusion location, thrombus burden, and vascular anatomy.[11] Hemodynamic support, including balloon occlusion or temporary flow arrest, may be used to enhance safety during retrieval.[1] Upon completion, the access site is closed with manual compression or closure devices, followed by intensive care monitoring for reperfusion-related complications such as hemorrhage or edema.[11]Physiological Rationale
Thrombectomy addresses acute ischemic stroke by mechanically extracting occlusive thrombi from large cerebral vessels, thereby restoring antegrade cerebral blood flow (CBF) to ischemic brain regions.[1] In large vessel occlusion (LVO), the thrombus impedes perfusion, leading to rapid onset of hypoxia and nutrient deprivation in downstream parenchyma, which initiates a cascade of cellular injury including ATP depletion, ionic imbalance, excitotoxicity, and inflammation.[13] The ischemic territory comprises an infarct core—where CBF falls below 10-12 mL/100g/min, rendering tissue irreversibly damaged within minutes—and a surrounding penumbra, where CBF is reduced to 10-20 mL/100g/min but maintained above the viability threshold via collateral circulation, allowing delayed neuronal death if reperfusion is not achieved.[14][1] The core physiological benefit of thrombectomy lies in salvaging this penumbra by achieving rapid recanalization, which elevates CBF to levels sufficient to halt progression to infarction and mitigate secondary injury mechanisms such as reperfusion-induced oxidative stress and edema.[13] Unlike intravenous thrombolysis, which relies on pharmacological dissolution and may fail in dense clots, mechanical removal ensures high rates of substantial reperfusion (e.g., modified Thrombolysis in Cerebral Infarction score ≥2b), directly countering the time-dependent expansion of the infarct core into penumbral zones.[15] Studies confirm that penumbral preservation correlates with improved functional outcomes, as timely restoration of perfusion preserves neuronal integrity and metabolic homeostasis in collateral-dependent regions.[14][16] This rationale extends from first-principles of cerebral autoregulation and oxygen delivery: normal gray matter requires CBF >20 mL/100g/min for electrophysiological function and >55 mL/100g/min for protein synthesis; thrombectomy-induced reperfusion exceeds these thresholds in viable tissue, averting oligemia-induced dysfunction while minimizing risks like hemorrhage in already necrotic core areas.[1] In non-cerebral applications, such as peripheral artery thrombosis, the principle similarly hinges on reversing limb- or organ-threatening ischemia by clot extraction, though cerebral efficacy is uniquely tied to the brain's intolerance for even brief hypoperfusion due to high metabolic demand and limited collaterals in some patients.[13]Historical Development
Early Attempts and Pre-Endovascular Era
Surgical thrombectomy for acute ischemic stroke emerged in the mid-20th century as an attempt to mechanically restore blood flow in large cerebral vessel occlusions, predating catheter-based endovascular methods. The inaugural procedure targeted the middle cerebral artery (MCA), with E. Craig Welch reporting the first successful embolectomy in 1957, involving temporary vessel occlusion via craniotomy, arteriotomy, and manual clot extraction using forceps or suction under direct visualization.[17] This approach built on earlier peripheral arterial embolectomies but faced unique challenges in intracranial vessels, including limited surgical access and the fragility of cerebral circulation. Initial cases demonstrated technical feasibility in restoring patency, yet reliance on clinical symptoms alone for diagnosis—without computed tomography or magnetic resonance imaging—often delayed intervention, exacerbating ischemic damage.[18] Subsequent advancements incorporated microsurgical techniques in the 1960s, enhancing precision during clot removal. Jacobson et al. described an MCA embolectomy in 1962, emphasizing the use of operating microscopes to minimize endothelial trauma and ischemia time during clamping, which typically lasted 10-20 minutes.[19] For proximal internal carotid artery (ICA) occlusions, surgical exposure via cervical incision proved more straightforward, with Meyer et al. reporting successful embolectomy in 1962, achieving recanalization through balloon catheter assistance or direct extraction.[17] Pioneers like M. Gazi Yasargil further refined intracranial procedures, performing early microvascular embolectomies that integrated magnification and finer instrumentation, though these remained experimental and case-specific.[20] Despite technical successes in small series, outcomes were generally poor due to inherent limitations: most patients presented beyond 6 hours from symptom onset, when irreversible infarction had occurred, and procedures carried risks of reperfusion hemorrhage, vessel spasm, and perioperative stroke extension. Pre-1990 reports documented recanalization in 50-70% of attempted cases, but mortality rates approached 40% and favorable functional recovery (e.g., modified Rankin Scale 0-2) occurred in under 30%, underscoring the method's selectivity for young patients with minimal comorbidities and embolic rather than thrombotic occlusions.[18] [17] Surgical thrombectomy thus served as a proof-of-concept for mechanical revascularization but waned in favor as neuroimaging improved diagnosis and non-invasive therapies like intravenous thrombolysis gained traction, relegating open techniques to rare, adjunctive roles in the pre-endovascular landscape.[21]Endovascular Era and Pivotal Trials
The endovascular era of mechanical thrombectomy for acute ischemic stroke emerged in the mid-2010s, driven by refinements in stent-retriever technology and improved patient selection via advanced imaging, which addressed limitations of prior trials using first-generation devices like the Merci retriever. Earlier multicenter randomized controlled trials, such as IMS III (published 2013), had failed to demonstrate superiority of intra-arterial therapy over intravenous alteplase alone, with neutral functional outcomes attributed to delayed treatment times, suboptimal reperfusion rates, and inclusion of heterogeneous occlusions. In contrast, subsequent studies leveraged retrievable stents (e.g., Solitaire FR) for higher recanalization success (often >80%) and emphasized proximal anterior circulation large-vessel occlusions with salvageable penumral tissue. The landmark Multicenter Randomized Clinical Trial of Endovascular Treatment for Acute Ischemic Stroke in the Netherlands (MR CLEAN), published December 17, 2014, provided the first robust evidence of benefit. This phase 3, multicenter trial randomized 500 patients with proximal intracranial arterial occlusion (internal carotid or middle cerebral artery) within 6 hours of onset to intra-arterial treatment plus standard care versus standard care alone; 89% of the intervention group received intravenous alteplase if eligible. The primary outcome was modified Rankin Scale (mRS) score at 90 days, with the intervention group showing a shift toward better outcomes (common odds ratio 1.67, 95% CI 1.21-2.30; P<0.001), including 32.6% achieving mRS 0-2 versus 19.1% in controls.[22] Two-year follow-up confirmed sustained benefits, with reduced mortality and disability.[23] Building on MR CLEAN, four pivotal trials published in 2015—ESCAPE, EXTEND-IA, SWIFT PRIME, and REVASCAT—replicated and extended these results in more rigorously selected cohorts, focusing on rapid intervention (median door-to-groin times <90 minutes) and imaging criteria like Alberta Stroke Program Early CT Score (ASPECTS) ≥6 or perfusion mismatch to identify small infarct cores with favorable collaterals. The ESCAPE trial (Randomized Assessment of Rapid Endovascular Treatment of Acute Stroke), reported February 11, 2015, enrolled 237 patients with small-core infarcts and good collaterals within 12 hours; endovascular therapy yielded 53% mRS 0-2 at 90 days versus 29% with medical management (odds ratio 4.40, 95% CI 2.61-7.40; P<0.001), alongside reduced mortality (10.4% vs. 19.0%).[24] EXTEND-IA reported 71% mRS 0-2 with thrombectomy versus 40% controls (RR 2.6, 95% CI 1.2-5.6; P=0.01), SWIFT PRIME showed 60% versus 35% (OR 5.1, 95% CI 2.8-9.3), and REVASCAT 44% versus 28% (aOR 2.1, 95% CI 1.1-4.0), all using stent retrievers primarily. [25]| Trial | Publication Date | Sample Size | Time Window | Key Selection/Method | Primary Outcome (mRS 0-2 at 90 days) |
|---|---|---|---|---|---|
| MR CLEAN | Dec 2014 | 500 | ≤6 hours | Proximal occlusion; stent retriever ± IA tPA | 33% vs. 19% (OR 1.67) |
| ESCAPE | Feb 2015 | 237 | ≤12 hours | Good collaterals/small core; rapid EVT | 53% vs. 29% (OR 4.40) |
| EXTEND-IA | Feb 2015 | 70 | ≤6 hours | Perfusion mismatch; stent retriever | 71% vs. 40% (RR 2.6) |
| SWIFT PRIME | Jun 2015 | 196 | ≤6 hours | ASPECTS ≥6; stent retriever | 60% vs. 35% (OR 5.1) |
| REVASCAT | Jun 2015 | 206 | ≤8 hours | Proximal occlusion; stent retriever | 44% vs. 28% (aOR 2.1) |
Endovascular Techniques
Stent-Retriever Methods
Stent-retriever methods employ self-expanding nitinol mesh devices delivered endovascularly to engage and extract occlusive thrombi, primarily in large-vessel acute ischemic stroke. These second- and third-generation devices, such as Solitaire (Medtronic) and Trevo (Stryker), feature laser-cut or braided structures with closed- or open-cell designs that provide radial force for vessel wall apposition and clot integration.[26][27] The mechanism involves advancing a microcatheter and microwire across the thrombus under fluoroscopic guidance, followed by deployment of the compressed stent-retriever distal to the occlusion. Upon release, the device expands to diameters matching the vessel (typically 3-6 mm), exerting chronic outward force (approximately 0.01 N/mm) to embed into the thrombus, often slicing through fibrin-rich components and restoring 33-50% of baseline antegrade flow within seconds.[28][26] Clot-device integration occurs over 3-5 minutes via mechanical interlocking and potential adhesive forces from thrombus deformation, enabling retrieval as a unit.[28] Retrieval proceeds by slowly withdrawing the integrated assembly into a proximal guide catheter (positioned in the cervical internal carotid artery), frequently augmented by manual aspiration through the guide or a balloon guide catheter (BGC) for temporary flow arrest, which reduces distal embolization risk by 21-57%.[27][28] First-pass recanalization rates reach 72-89% with these devices, outperforming earlier retrieval systems like MERCI (48-58%).[26] Clinical efficacy is evidenced by pivotal trials such as MR CLEAN (2015), where stent-retriever use yielded 32.6% good functional outcomes (modified Rankin Scale ≤2 at 90 days) versus 19.1% with medical therapy alone, with recanalization in 58.7% of cases.[25] Similar benefits appeared in ESCAPE and SWIFT PRIME, attributing success to immediate reperfusion minimizing ischemic penumbra expansion.[26] Device variations, including dual-layer designs like EmboTrap, aim to enhance first-pass effects (up to 84.6% recanalization), though comparative superiority remains under evaluation in ongoing studies.[26] For refractory occlusions, techniques like double stent-retriever deployment or combined "Solumbra" (stent-retriever plus direct aspiration) improve success, with the latter achieving 83.6% reperfusion in registries.[27] BGC use further boosts outcomes, increasing favorable 90-day modified Rankin Scale scores by up to 30%.[28] Limitations include procedure times of 20-40 minutes and dependency on clot composition, with fibrin-rich thrombi resisting integration in 20% of cases.[28]Direct Aspiration Approaches
Direct aspiration thrombectomy entails advancing a large-bore aspiration catheter to the proximal face of an intracranial thrombus and applying continuous negative pressure via a dedicated pump to achieve en bloc clot retrieval, often without initial reliance on stent retrievers.[29] This approach leverages the thrombus's adherence to the vessel wall under suction, aiming for rapid revascularization in acute ischemic stroke due to large vessel occlusion.[30] Unlike stent-retriever methods, direct aspiration minimizes device manipulation within the vessel, potentially reducing endothelial trauma and procedural time.[31] The A Direct Aspiration first Pass Technique (ADAPT), first described in 2013, exemplifies this strategy as a frontline intervention, employing aspiration alone for initial clot removal and reserving stent retrievers for rescue if needed.[31] In ADAPT protocols, a 0.068- to 0.070-inch inner diameter catheter is navigated over a microwire to the occlusion site, with suction initiated to collapse the vessel distally and extract the thrombus.[32] Commercial systems, such as the Penumbra System with ACE or JET reperfusion catheters connected to an aspiration pump, facilitate this by providing consistent vacuum levels up to -28 inHg, enabling retrieval of clots in anterior circulation occlusions like the middle cerebral artery.[33] Evolving catheter designs, including those with distal access and flexible tips, have improved navigability and first-pass efficacy, with reported successful reperfusion rates after a single aspiration pass reaching 53-60% in internal carotid or M1 segment cases.[34] Clinical evidence supports ADAPT's noninferiority to stent-retriever thrombectomy, with 90-day functional independence (modified Rankin Scale 0-2) rates of approximately 50-60% in eligible patients, alongside high recanalization (TICI 2b-3) in 70-95% overall.[32][35] A first-pass effect—complete recanalization on the initial attempt—occurs in over 55% of cases and correlates with improved outcomes, including lower symptomatic intracranial hemorrhage rates (around 5%) compared to multi-pass or combined techniques.[36][37] Direct aspiration also demonstrates cost-effectiveness, reducing procedural expenses by about $5,000 per case through fewer consumables, without compromising reperfusion (achieved in 94.6% of patients across 1.9 median passes).[38] In scenarios of aspiration failure (e.g., fragmented or adherent clots), adjunctive stent deployment or balloon angioplasty yields rescue success in most instances, underscoring the technique's role as a foundational step.[39] Predictors of aspiration success include thrombus location in M1-M2 segments, smaller clot burden, and absence of calcification, with failure more common in distal or posterior circulations requiring technique adaptation.[36]Combined and Adjunctive Strategies
Combined mechanical thrombectomy techniques integrate contact aspiration with stent-retriever deployment to optimize clot engagement and removal, particularly for large-vessel occlusions in acute ischemic stroke. In this approach, a stent retriever is deployed to capture the proximal thrombus while simultaneous aspiration through a large-bore catheter addresses distal fragments or adherent clot material, potentially reducing embolization and improving immediate recanalization.[40] Meta-analyses of observational data indicate that combined aspiration and stent-retriever methods yield superior first-pass reperfusion rates compared to stent-retriever monotherapy, with successful recanalization (modified Thrombolysis in Cerebral Infarction [mTICI] score ≥2b) achieved in up to 70-80% of cases in some series.[41] Randomized trials, however, have produced mixed results on overall efficacy. The ASTER trial, involving 408 patients with anterior circulation large-vessel occlusion, found that initial combined contact aspiration and stent-retriever thrombectomy did not significantly increase the rate of near-total or total reperfusion (expanded TICI [eTICI] 2c/3: 64.5% vs. 57.9%; adjusted odds ratio 1.33, 95% CI 0.88-1.99) compared to stent-retriever alone, though initial successful reperfusion (eTICI ≥2b after first pass) was higher (86.2% vs. 72.3%). Functional independence at 90 days (modified Rankin Scale [mRS] 0-2) was similar between groups (38.0% vs. 41.9%), with the combined approach associated with fewer parenchymal hematomas type 2 (3.1% vs. 8.6%).[42] Subsequent analyses suggest combined techniques may benefit specific subgroups, such as posterior circulation occlusions, where first-line combined approaches improved recanalization in observational cohorts.[43] Adjunctive pharmacological strategies aim to mitigate microvascular thrombosis or incomplete reperfusion following mechanical thrombectomy, often targeting residual distal emboli. Intra-arterial thrombolysis (IAT) with agents like alteplase or urokinase after endovascular therapy has demonstrated improved excellent functional outcomes (mRS 0-1 at 90 days) in patients with successful but suboptimal reperfusion, as evidenced by the CHOICE trial, which reported enhanced recovery without a significant increase in symptomatic intracranial hemorrhage.[44] Ongoing trials, such as POST-UK evaluating intra-arterial urokinase post-thrombectomy, continue to assess safety and efficacy in large-vessel occlusion, with preliminary data suggesting potential quality-of-life benefits.[45] Intra-arterial antithrombotic therapy during thrombectomy, including glycoprotein IIb/IIIa inhibitors like tirofiban or eptifibatide, seeks to promote microvascular reperfusion but carries elevated hemorrhage risks without consistent functional gains; the MR CLEAN-MED trial found increased symptomatic intracranial hemorrhage with periprocedural heparin and aspirin.[44] Intravenous thrombolysis prior to thrombectomy (bridge therapy) remains standard for eligible patients, with trials confirming its safety and potential synergy in extending treatment windows up to 4.5 hours from onset. Emerging adjuncts, such as normobaric hyperoxia or neuroprotectants like nerinetide, show promise in reducing infarct volume or improving outcomes in non-thrombolysis cohorts but require further validation.[44] Overall, adjunctive use is reserved for incomplete recanalization cases due to hemorrhagic risks, with selection guided by reperfusion grades and patient factors.Clinical Applications
Acute Ischemic Stroke
Endovascular thrombectomy is the standard of care for acute ischemic stroke due to large vessel occlusion (LVO) in the anterior circulation, targeting thrombi in the intracranial internal carotid artery or middle cerebral artery M1 segment to restore perfusion and mitigate infarct progression.[12] Eligible patients typically present with a National Institutes of Health Stroke Scale (NIHSS) score of 6 or higher, Alberta Stroke Program Early CT Score (ASPECTS) of 6 or greater on non-contrast CT to indicate limited early infarct, and minimal prestroke disability (modified Rankin Scale [mRS] score 0-1).[46] Confirmation of LVO via CT angiography or magnetic resonance angiography is required, with the procedure often combined with intravenous alteplase if initiated within 4.5 hours of symptom onset and no contraindications exist.[47] In the early time window (0-6 hours from last known well), American Heart Association/American Stroke Association (AHA/ASA) guidelines provide class I recommendation for thrombectomy in patients meeting imaging and clinical criteria, independent of thrombolysis eligibility, due to superior recanalization rates over medical management alone.[47] For the extended window (6-24 hours), patient selection incorporates advanced imaging such as CT perfusion or MRI to demonstrate favorable mismatch profiles—small core infarct (e.g., <70 mL in patients under 80 years or <100 mL in older patients with lower NIHSS) relative to hypoperfused tissue—aligning with criteria from trials validating efficacy beyond traditional timelines.[48] Application extends to posterior circulation LVO, including basilar artery occlusion, where thrombectomy is recommended up to 24 hours in select cases with viable brainstem tissue on imaging, reflecting improved survival and functional outcomes compared to anticoagulation or thrombolysis.[49] Recent expansions include patients with larger infarct cores (ASPECTS 2-5 or core volumes 50-100 mL), where 2025 AHA guidelines endorse thrombectomy based on randomized evidence showing net benefit despite higher periprocedural risks.[48] Clinical outcomes demonstrate thrombectomy's efficacy, with meta-analyses of trials in LVO stroke reporting odds ratios of 2.0 to 2.5 for achieving functional independence (mRS 0-2 at 90 days) versus best medical management, translating to 20-30 additional independent patients per 100 treated in eligible cohorts.[50] Long-term follow-up confirms sustained benefits, including reduced mortality and disability, particularly when reperfusion is achieved early in the procedure (e.g., extended Thrombolysis in Cerebral Infarction score 2b-3).[50] Transfer protocols to comprehensive stroke centers are emphasized to minimize door-to-groin puncture times, targeting under 90 minutes for direct arrivals and 60 minutes for drips-and-ships.[47]Peripheral and Pulmonary Indications
Thrombectomy in peripheral vascular disease is primarily indicated for acute limb ischemia (ALI) resulting from arterial thromboembolism, where rapid restoration of blood flow is essential to salvage limb viability and prevent amputation. According to Rutherford classification, catheter-based thrombolysis or mechanical thrombectomy may be considered for category IIb ALI of greater than 14 days' duration, particularly when surgical options are limited or contraindicated.[51] Devices such as the Indigo Aspiration System have demonstrated safety and efficacy in treating lower extremity arterial occlusions, with technical success rates exceeding 90% in observational studies involving patients with Rutherford IIa-III ischemia, achieving limb salvage in most cases while minimizing distal embolization risks through continuous aspiration.[52] Mechanical thrombectomy using rotational devices like Rotarex has been evaluated in acute and subacute occlusions, showing patency restoration in up to 88% of cases across 16 clinical studies, though evidence remains largely from non-randomized data emphasizing its role in reducing thrombolytic-related bleeding compared to pharmacomechanical approaches.[53] The 2024 ACC/AHA guidelines for lower extremity peripheral artery disease endorse endovascular revascularization, including thrombectomy, for symptomatic ALI, prioritizing it in patients with viable or marginally threatened limbs to optimize outcomes over open surgery.[54] In pulmonary embolism (PE), mechanical thrombectomy serves as an interventional option for high-risk cases with hemodynamic instability, such as massive PE causing shock or cardiac arrest, where systemic thrombolysis is contraindicated, ineffective, or carries excessive bleeding risk.[55] The 2019 ESC guidelines recommend catheter-directed therapies, including aspiration thrombectomy, for high-risk PE when thrombolysis fails or is contraindicated, with recent updates elevating standalone aspiration thrombectomy to a class I indication for such patients due to its ability to rapidly reduce right ventricular strain without adjunctive fibrinolysis.[56] Suction thrombectomy using large-bore catheters has shown hemodynamic improvements in intermediate- and high-risk PE, with procedural success rates of 90-100% in reducing pulmonary artery pressure and right ventricular/left ventricular ratio, as evidenced in multicenter registries and the PEERLESS trial, which compared large-bore mechanical thrombectomy to catheter-directed thrombolysis in 550 intermediate-risk patients, demonstrating noninferiority in clinical outcomes with fewer 30-day readmissions (3.2% vs. 7.9%).[57][58] Catheter-directed thrombectomy without thrombolysis further supports efficacy in meta-analyses, yielding favorable safety profiles with major bleeding rates below 2% and mortality reductions in acute PE cohorts.[59] These approaches are particularly valuable in submassive PE with right ventricular dysfunction, offering a bridge to recovery when anticoagulation alone is insufficient.[60]Evidence of Efficacy
Randomized Controlled Trials
The pivotal randomized controlled trials establishing the efficacy of endovascular thrombectomy for acute ischemic stroke with large vessel occlusion were conducted primarily between 2014 and 2015, demonstrating superior functional outcomes compared to intravenous thrombolysis alone or best medical management. The Multicenter Randomized Clinical Trial of Endovascular Treatment for Acute Ischemic Stroke in the Netherlands (MR CLEAN), published in December 2014, was the first to show a significant benefit, with 232 patients randomized to intra-arterial treatment plus usual care versus usual care alone; the adjusted common odds ratio for improved modified Rankin Scale (mRS) score at 90 days was 1.67 (95% CI, 1.21-2.30), indicating higher rates of functional independence (32.6% vs. 19.1%).[22] This trial included patients with proximal anterior circulation occlusion confirmed by CT angiography, treated within 6 hours of symptom onset, and used various thrombectomy devices.[22] Concurrent trials reinforced these findings using advanced imaging for patient selection and stent-retriever technology. The Endovascular Treatment for Small Core and Proximal Occlusion Ischemic Stroke (ESCAPE) trial, stopped early for efficacy in 2015, enrolled 316 patients across 22 centers, randomizing them to rapid endovascular therapy or standard care; at 90 days, the adjusted common odds ratio for mRS shift was 2.26 (95% CI, 1.39-3.68), with 53% achieving functional independence (mRS 0-2) in the intervention group versus 29% in controls.[24] Similarly, the Extending the Time for Thrombolysis in Emergency Neurological Deficits - Intra-Arterial (EXTEND-IA) trial, also in 2015, used perfusion imaging to select 70 patients with small ischemic cores and mismatch; reperfusion rates were higher (86% vs. 49%), and the mRS odds ratio was 2.6 (95% CI, 1.0-6.5), though limited by small sample size.[61] The Solitaire with the Intention for Thrombectomy as Primary Endovascular Treatment (SWIFT PRIME) trial, reported in 2015, randomized 196 patients post-thrombolysis to stent-retriever thrombectomy or t-PA alone, yielding a 60% rate of mRS 0-2 at 90 days versus 35% (OR 5.1, 95% CI 2.5-10.6).[25] Pooled analyses of these early trials confirmed consistent benefits, with an overall number needed to treat of about 8 for one additional patient achieving functional independence, alongside acceptable safety profiles including symptomatic intracranial hemorrhage rates of 6-7%.[62] Subsequent RCTs expanded indications to later time windows (up to 24 hours) and larger infarct cores, such as DAWN and DEFUSE 3 in 2018, which used mismatch criteria and showed mRS benefits (e.g., DAWN: 49% vs. 13% mRS 0-2; OR 2.77, 95% CI 1.60-4.80).[63] More recent trials for large-core strokes (e.g., SELECT2, RESCUE-Japan LIMIT in 2023-2024) further validated efficacy, with meta-analyses reporting improved 90-day mRS (OR 1.53-2.0) and reduced mortality despite higher baseline risks.[7][64]| Trial | Year | Key Eligibility | Primary Outcome (90-day mRS) | Key Result |
|---|---|---|---|---|
| MR CLEAN | 2014 | LVO within 6h, ASPECTS ≥2 | Shift in mRS | OR 1.67 (95% CI 1.21-2.30); 32.6% vs. 19.1% mRS 0-2[22] |
| ESCAPE | 2015 | LVO with good collaterals, within 12h | Shift in mRS | OR 2.26 (95% CI 1.39-3.68); 53% vs. 29% mRS 0-2[24] |
| EXTEND-IA | 2015 | Perfusion mismatch, within 4.5h post-tPA | Shift in mRS | OR 2.6 (95% CI 1.0-6.5); 71% vs. 40% mRS 0-2[61] |
| SWIFT PRIME | 2015 | LVO post-tPA, within 6h | Rate of mRS 0-2 | 60% vs. 35%; OR 5.1 (95% CI 2.5-10.6)[25] |