Stent Retrievers, Aspiration Catheters & Promising New Devices for Stroke Thrombectomy

[Dr. Michael Barraza]:
All right. So both of you have clearly played an integral role in the evolution of optimal stroke therapy, and so the question is today, what do we consider optimal in terms of technique and equipment and doing stroke thrombectomy? And I learned with stent retrievers first, specifically the solitaire, and then it changed practices. As you know, the vast majority of these were done with aspiration first with the penumbra system, and more recently with imperative care zoom catheters, which Dr. Gounis is familiar with having published a paper on the efficacy of those. They're fantastic catheters, but the point of all this is that I didn't really notice any difference in terms of efficacy in technical or clinical success between these two different systems, and I don’t know if that’s anecdotal, but it's really not just me. And, you know, we have all these case series and trials with catchy names (my favorite being the BADASS technique, CAPTIVE, and SAVE), and they all propose some combination of stent retrievers, balloon guides, and aspiration catheters as the best way to remove clot. But to me, it seems like there's no real convincing data that establishes any of these is superior. Do you guys agree or am I missing something?

[Dr. Hannes Nordmeyer]:
So I think we're still struggling with the most effective method to pull clots, right? So, we tried out anything: pure stent retriever in combination with balloon guiding catheters, double stent retriever techniques, SAVE techniques, pure aspiration. And I had the fortune to work with René Chapot for many years, and we went for double retriever techniques. Really in the early years of thrombectomy, when we failed to retrieve the clot within the first two or three maneuvers, we deploy two stent retrievers in parallel to untangle the clot in between of them. And we had really high success rates with that, and, yes, I think nowadays, the need is really to have one retriever that makes it all, right?

[Dr. Matthew Gounis]:
I can elaborate a little bit on that, in that, I think at estimate, we had the good fortune to hear the SWIFT DIRECT study. And what I took away from that is that it was really compelling that up to 97% of successful recanalization, which is defined as TICI 2b/3. So the techniques and the equipment have gotten remarkably good. I think we need to change the definition of success, which is what Dr. Nordmeyer just said, and that should be first pass TICI 2c/3because that's what we know is going to impart the greatest benefit to the patient.

[Dr. Michael Barraza]:
Yeah, I think that's a really important point. Dr. Nordmeyer, for a standard large vessel occlusion what is your normal setup in terms of equipment?

[Dr. Hannes Nordmeyer]:
We have mainly two setups. In patients with straight cervical vessels, we go for balloon guide catheter and a stent retriever technique. If there is any anatomical reason, like extremely torturous ICA, where a balloon guiding really doesn't make any sense because aspirating from below, with all the vasculature distal to it, having been stretched and being in a ventralposition, doesn't make sense. We go for a triaxial access with a guiding catheter, aspiration catheter, and the microcatheter for the stent retriever. So, this is mainly the approach for easy and difficult anatomical situations, and then it's really up to the location of the thrombus and the behavior of clot within the first one or two maneuvers, whether to change the method or to go on with the stent retrieving approach.

[Dr. Michael Barraza]:
Same with me. Are either of you aware of any techniques or equipment on the horizon that looked like they could distinguish themselves over the rest?

[Dr. Matthew Gounis]:
Yeah, I'd be happy to respond to that one. There’s a new series of aspiration catheters that are very, very large bore, like 088 aspiration systems. And I think the newest technology that we're evaluating and it’s in its beginning in terms of clinical experience with the millipede catheter being tested in Ireland and the route 92 catheter being tested in the United States. I think that reliable navigation of these super large bore catheters to the middle cerebral artery is going to be realized in the near future. And I think, again, it's lending us towards what I said as the definition of success, which is TICI 2c/3 at the first pass.

[Dr. Michael Barraza]:
That's interesting. Dr. Gounis, you've also done a lot of research on intravascular imaging. With either optical CT or even more traditional like IVUS, can you tell if that, clot composition or anything from them, before we start trying to remove these clots, which ones are going to be harder to pull?

[Dr. Matthew Gounis]:
Yes, so, we've looked into it. So just to be clear, the existing optical coherence tomography technology that's clinically available and the existing IVUS systems are really not designed and not appropriate for intracranial use, so anything beyond the carotid siphon. You'll see scattered case reports of OCT being used in the intradural space, but nothing ever distal to the siphon, and the reason is because of the tortuosity. Those catheters, essentially the fiber that spins the lens, it can't work in that extreme tortuosity, but we are introducing a new neurovascular technology that'll be available probably within a year. It's a very exciting system. It's basically an 014 wire that has the optical engine in it. And we have looked into it, and I think it's going to be primarily useful in the setting of stroke when you have multiple failed passes, and it's not a tough clot, but rather there's an underlying atheroma or a dissection. That's where I think this technology may be particularly useful is to look at those underlying vascular etiologies that are not cardioembolic or large artery, generated emboli.

[Dr. Michael Barraza]:
Dr. Nordmeyer, what other tactical or patient specific elements can result in a challenging or unsuccessful thrombectomy?

[Dr. Hannes Nordmeyer]:
As I said, anatomy is really an issue. So if we have very tortuous vessels, like an elongated and one segment that is really dipping downwards and then pointing upwards again, we know that all techniques available on the market have a high percentage of failure in these occlusions. So if the anatomy is against us, there's still really the need to go again and again and again for the retrieval and to escalate the therapy by switching to a more aggressive device that has higher radial force or another architecture like the Nimbus or to go for double retriever techniques and really trying to advance a large bore aspiration catheter as close to the thrombus as possible to apply as much aspiration force to the thrombus as you can. But I think what Dr. Gounis just said thrombus imaging with an 014 wire is giving us some information on whether there's atheroma or just tough a clot, for example, that could be a real game changer. So if we're having had four or five or six unsuccessful passes, and we know that the reason for it is the atheroma, we would straight go for stenting, of course. So it still might be very challenging to get up a PTA balloon up there in torturous anatomy, but having early information on the reason of the occlusion that can accelerate the whole procedure and prevent us from spending time on several thrombectomy maneuvers, if we know that stenting and angioplasty would be the right thing to do.