By Rajiv Advani MD PhD FESO, Norway Twitter: @rajeroni
The final day of the ESO-WSO 2020 Congress and a live joint ESO-ESNR session on Mechanical Thrombectomy (MT) and Imaging Selection.
Imaging in The Pre-Hospital Phase – A Look to The Future
Prof. Geoffrey Donnan from Australia kicked off the session with a presentation on new technologies in the development of diagnostics in acute ischemic stroke. The Golden Hours of Ischemic stroke; the first hour since the onset of symptoms in the setting of intravenous thrombolysis (IVT) and the first two hours in the case of MT. This time window yields the best results in terms of clinical outcomes. But the question remains, how do we access the Golden Hours? The answer – improved pre-hospital care, new technology incorporated into new transport options and improved data linkage. Around 30 Mobile Stroke Units (MSU) are currently operating around the world. MSU results in Melbourne, Australia have shown IVT treatment rates around 50% and MT treatment rates of around 25%. Incorporating new technologies into MSU has proven to be extremely clinically effective whilst also providing significant monetary savings. Faster clot retrieval drives the majority of these results but is also augmented by faster IVT administration. New technologies include light weight CT scanners around a fifth of the weight of a traditional scanner and the use of electromagnetic (EM) imaging. Electromagnetic imaging employs (EM) phase shift to visualise strokes and can differentiate between haemorrhagic and ischemic strokes. Get technology out there to the patients and reduce treatment times; a resounding yes to the Golden Hours!
Stroke Imaging: How to Predict Futile Recanalization?
Prof. Raul Nogueria from the USA continued the session with a presentation on the predictability of futile recanalization. Prof. Nogueria started off with the question ‘Can it be done?’ Can futile reperfusion be predicted using imaging, the answer; ‘In early time window, it shouldn’t be attempted’. Medical futility is the unacceptable likelihood of achieving a treatment benefit. Quantitative futility is defined as a less than 1% chance of a favourable outcome. When NNTs for MT are as low as 3, should we even try to predict futility in the early time window? As a physician futility should not be confused with cost effectiveness. Loss of grey and white matter differentiation on non-contrast enhanced CT is the only marker of established infarct core. Further analyses of patients included in MT RCT’s have shown that 85% of patients have favourable imaging, should we be trying to find the remaining 15%? CT Perfusion and MRI DWI have been shown to visualise ghost cores and exclude patients from treatment. More imaging confuses the issue, be aware of the ghost core phenomenon and never exclude patients based on CTP alone within the early time window.
ICI2b or TICI3; Time to Redefine Successful Reperfusion to Conclude Intervention
Prof. Johannes Kaesmacher from Switzerland continued with a poignant presentation on the redefinition of successful reperfusion. The question is TICI2b or TICI3, and when to settle for TICI2b. TICI2c is somewhere in between 2b and 3, and is rapidly being incorporated into daily MT terminology. To improve recanalization from grade 2b after the first attempt to a TICI 3 requires further attempts and leads to increased procedure times. Increased procedure times and a greater number of attempts are both independently associated with poorer outcomes. In this setting it is also important to consider the causality of poor collaterals. A primary TICI 3 is the ideal result but going for a secondary improvement from TICI 2b to TICI3 is potentially not worth the time used. The NNT to achieve this secondary improvement is 10 in some observational studies, but as high as 20 in other observational data sets. Remember that there are a couple of options for the TICI2b patient subset; continue MT, administer IA thrombolytics or settle for 2b. TICI2b should be accepted more often and more importantly it should be accepted earlier with fewer attempts!
The Role of First Pass Recanalization
Prof. Jens Feihler from Germany continued the session with a presentation on the role of first pass recanalization. The message was clear from the outset; the new goal is TICI3 at the first attempt. Just some years ago the standard used to be TICI2b at any time, then TICI3 at any time and now we move forward to TICI3 at the first attempt. First pass TICI3 increases the chances of a good outcome by 20% as compared to first pass TICI2b. But how do we get there? Which factors should we consider? An array of techniques exist; SOLUMBRA, SAVE, ARTS, CAPTIVE and PROTECT. A sound understanding of the techniques and their use is pivotal. Observational data show that the use of a balloon guide catheter leads to higher rate of TICI3 outcomes at the first attempt. Furthermore, Catheter to Vessel ratio is important, the tighter the fit – the better the result. The phenotype of the occlusion, clean cut or claw type, is also important to consider. Aspiration works better on flatter more clean cut occlusions and claw type occlusions respond better to stent retrievers. Keep in mind that beyond the third retrieval attempt clinical outcomes can become worse, and after the sixth attempt an increase in mortality rates can be seen. The take home message; get it right the first time around!
Stenting in Tandem Occlusions: A Bail or Thread?
Prof. Pasquale Mordasini from Switzerland concluded the session with a presentation on acute stenting in the setting of tandem occlusions. Tandem occlusions make up almost 20% of major strokes and respond poorly to IVT treatment. Treatment options therefore include MT with or without acute stenting. A recent meta-analysis showed that better clinical outcomes were seen at 90 days with the use of acute stenting. But what are the pros; it stops recurrent stroke, more rapidly improves perfusion pressure, and contributes to clot lysis. Additionally, acute stenting serves as a ‘one stop treatment’ without the uncertainty of TEA delay. The cons; acute stenting delays intracranial access and can lead to a larger infarct as well as new emboli during the stenting procedure. There is little or no RCT data on this subject and two new RCTs are currently in the planning phase; TITAN and EASI-TOC. Keep in mind that MT is equally effective in the setting of a tandem occlusion. Stent thrombi occur in about 20% of cases and more frequently in diabetics. Signs of stent thrombus formation on the final angiographic run is a poor prognostic marker. Remember to check for thrombus formation on the final run and address it immediately!
I would like to thank the distinguished presenters for a great live session with a lively discussion in the Q&A segment.