Report by Rajiv Advani MD PhD FESO, Norway Twitter: @rajeroni
The final day of the ESO-WSO 2020 Congress and a very relevant session on Mechanical Thrombectomy (MT).
The session focussed on some key issues surrounding mechanical thrombectomy (MT); Implications for Service in (Low Middle Income Country) LMIC’s, MT with or without the use of intravenous thrombolysis (IVT), Neuroprotection in Ischemic Stroke and its implications for MT and finally Imaging Selection for MT.
New Thrombectomy Devices – Implications for Service Provision in LMICs
Prof. Sheila Martins from Brazil began by telling us about how intravenous thrombolysis was implemented after its approval in 1994. We then heard about the difficulties of implementing thrombectomy in Brazil based on several key challenges such as overcrowded emergency rooms, the lack of dedicated angiography suites, a socioeconomically vulnerable population and the limited accessibility of rehabilitation services. Prof. Martins and her colleagues in Brazil decided to phase in MT using an RCT – the RESILIENT trial. They achieved a TICI2b/3 rate of 82%, a fantastic result, on par with those numbers seen in other trials such as DAWN and EXTEND IA. Earlier MT RCT’s have been performed in High Income Countries (HIC) representing about 20% of the world population. RESILIENT goes a long way to showing that MT can be safely and successfully implemented in LMIC’s.
Mechanical Thrombectomy Without TPA – Ready for Routine Use?
Prof. Urs Fischer from Switzerland talked us through MT with or without bridging therapy with IVT. IVT has several limitations such as limited or no effect on large central thrombi, a rapidly decreasing efficacy in the treatment time window and some relative / absolute contraindications; recent major surgery, severe CAA, known bleeding conditions, concurrent use of anticoagulants. In addition, does IVT lead to any pre-interventional reperfusion and if so to what degree? All these questions challenge decision making in the pursuit of personalised medical treatment for acute ischemic stroke. DIRECT-MT and SKIP trials published this year showed that IVT could potentially be dropped in favour of direct MT, but these trials had several real-world weaknesses. The future could hold other strategies such as the revival of intra-arterial thrombolytics, but more studies are needed to cement these treatment strategies. You are either a Bridging believer or a Bridging non-believer, but right now the advice is IVT before MT.
Adjunctive Approaches to Neuroprotection for Mechanical Thrombectomy
Prof. Italo Linfante from the USA talked us through ideas around neuroprotection for ischemic stroke and implications for MT. We heard about the time sensitive nature of MT in terms of achieving a favourable clinical outcome. This poses some important questions; how can we slow infarct progression and preserve penumbra? Is neuroprotection feasible in reducing neurotoxicity and improving collateral circulation? Several targets for neuroprotection have been identified, including glutamate receptors and secondary messengers. Nerinetide (NA1), an eicosapeptide that inhibits signalling in cell excitotoxicity was used in the ESCAPE NA1 trial, but showed no significant difference compared to placebo on functional outcomes. Several molecules including endothelial receptor agents and carboxyhaemoglobin oxygen carriers have been tested in animal models aimed at improving Collateral circulation (CC). They have shown promise in animal studies and increase the durability of CC thus slowing infarct progression; human trials are currently being planned.
Imaging Selection for Thrombectomy – By-Passing the Ct Scanner?
Prof. David Liebeskind from the USA presented imaging selection for MT. Imaging oversimplifies the complex and dynamic pathophysiology of an ischemic stroke. Imaging impacts patient care and is used to ‘predict’ outcome, but outcomes are individual and vary greatly. Imaging poses several interesting questions; Is imaging going to lead to a decision to not treat the ischemia? Furthermore, what imaging modality should be used and how will you use the information that modality gives you? The minimal requirement is an arterial occlusion and a thought that recanalization will result in a better clinical outcome than a persistent occlusion. Core and penumbra may not be as absolute as we think and therefore using imaging and AI learning to determine these variables is potentially harmful. Theranostics, the integration of therapeutics and diagnostics, can be achieved using angiography and potentially lead to bypassing the non-contrast enhanced CT. An interesting concept for the future is the TICI chronology for each MT pass, how the degree of recanalization is dynamically changing. Are we ready to trial direct to angiography in acute ischemic stroke?
On behalf of the ESO and WSO, I would like to thank the speakers for thought provoking presentations that inspired eager discussions.