In light of recent evidence indicating that thrombectomies with poor reperfusion may lead to inferior clinical outcomes versus medical management in ischaemic stroke, Adrien Guenego (Brussels, Belgium) assesses the need for a “fundamental change” over decision-making and how success is measured.
Based on multiple eligibility criteria, international guidelines recommend mechanical thrombectomy as the standard of care for acute ischaemic stroke. Since its introduction for anterior large vessel occlusion less than six hours after onset in 2015, indications and trials have expanded each year to large-core infarcts, late-time window strokes, and distal occlusions.
The techniques for mechanical thrombectomy have also evolved, with the development of specific devices such as large-bore catheters, mini-stent retrievers and distal aspiration catheters achieving successful reperfusion rates of over 70–80%, and a strong emphasis on improving the first-pass effect.
However, are we paying enough attention to the angiographic and tissue perfusion outcomes after mechanical thrombectomy? Is it sufficient to merely attempt recanalisation of an occluded vessel?
A fundamental change in how we approach and assess this procedure would represent a paradigm shift in mechanical thrombectomy for acute ischaemic stroke.
Recent history
The focus of previous randomised controlled trials (RCTs) was primarily on whether to perform a thrombectomy, and determining the correct indications for its application. In the 2016 HERMES meta-analysis, 71% of patients assigned to thrombectomy achieved successful reperfusion (modified thrombolysis in cerebral infarction [mTICI] score 2b or 3), meaning that, in 29% of cases, neurointerventionists experienced poor angiographic success and had to discontinue the treatment.1
In the early years of thrombectomy, the prevailing paradigm was to offer mechanical thrombectomy to selected patients and not necessarily to achieve full reperfusion at all costs. Indeed, the traditional approach since 2015 has primarily been to evaluate the appropriateness of attempting thrombectomy based on factors such as time elapsed since stroke onset, clot location, and the patient’s overall health.
This involved making multiple passes to achieve a successful recanalisation (mTICI 2b or higher) while minimising potential complications—how many times have we heard or said, “thrombectomy failure after ‘X’ number of attempts”? Achieving 100% complete reperfusion for all patients is, of course, an unattainable goal, as in any absolute position, and one should exercise caution when reviewing scientific manuscripts or commercial claims purporting such efficacy.
Yet, after eight years of increasing experience in mechanical thrombectomy, we still face uncertainties for 20–30% of our patients when complete recanalisation is not immediately achieved. Should we shift our focus not only to performing thrombectomy but also ensuring complete reperfusion for (nearly) each patient undergoing endovascular treatment? This transformation would significantly impact patient selection, the approach to endovascular treatment, and the evaluation of its effectiveness.
Switching gears
As scientific and clinical experience has advanced, there is mounting evidence that merely attempting a thrombectomy and achieving what we term a successful recanalisation (mTICI 2b or higher) may not be sufficient, and a failed attempt at recanalisation may even be harmful for the patient. A potential paradigm shift in light of this is driven by several factors:
- Reperfusion may extend beyond reopening the proximal blood vessel to salvaging at-risk brain tissue and distal small vessels
- Complete reperfusion is associated with better functional outcomes for stroke patients
- The composition (nature) of the clot can impact the quality of reperfusion
- Advances in imaging techniques, such as perfusion imaging and collateral assessment, enable clinicians to better assess the extent of ischaemic damage, and make informed decisions regarding thrombectomy and reperfusion strategies.
This shift toward complete reperfusion has driven more individualised treatment strategies, and sparked research and innovation in the field. These innovations include bail-out stenting in case of stent-retriever or aspiration failure; intra-arterial or intravenous lysis after mechanical thrombectomy; thrombectomy for secondary occlusions in distal vessels after a proximal endovascular treatment, and the use of neuroprotective medications.
While most of these strategies lack Level 1 evidence, they are under evaluation in prospective and retrospective trials. And, as Mayank Goyal (Calgary, Canada) and colleagues recently highlighted in a HERMES substudy—in case of acute ischaemic stroke with large vessel occlusion—endovascular treatment with poor reperfusion is inferior to medical management, but medical management is inferior to endovascular treatment with complete reperfusion.2
In summary, the shift from merely attempting a mechanical thrombectomy to striving for complete reperfusion necessitates a more patient-centred approach. This involves leveraging the full array of tools available to neurointerventionists to minimise the group of patients undergoing endovascular treatment who experience poor reperfusion. Patient selection, clinical judgment, and a careful evaluation of the treatment’s risks and benefits, remain crucial.
Every neurointerventionist should ask themselves: where should we “draw the line” in terms of reperfusion outcomes? Is TICI 2b sufficient? And, which factors influence my decision-making process before performing a thrombectomy?
References:
- Goyal M, Menon B K, van Zwam W H et al. Endovascular thrombectomy after large-vessel ischaemic stroke: a meta-analysis of individual patient data from five randomised trials. Lancet. 2016; 387(10029): 1723–31.
- Rex N, Ospel J M, Brown S B et al. Endovascular therapy in acute ischemic stroke with poor reperfusion is associated with worse outcomes compared with best medical management: a HERMES substudy. J Neurointerv Surg. 2023. doi: 10.1136/jnis-2023-020411.
Adrien Guenego is an interventional and diagnostic neuroradiologist at the Université libre de Bruxelles’ Hôpital Erasme in Brussels, Belgium.
The author declared no relevant disclosures.
