NeuroVoices: Young Lee, MD, on Applying Newly FDA Cleared THUNDERBOLT Stroke Thrombectomy

In early July, University Medical Center New Orleans became the first hospital in the country to use the THUNDERBOLT, Penumbra's newly FDA-cleared computer-assisted vacuum thrombectomy (CAVT) platform for the treatment of acute ischemic stroke. By design, the system uses modulated aspiration driven by computer algorithms to detect and fatigue blood clots, aiming to achieve complete clot ingestion without repeated catheter passes.

Overall, the clearance marked a meaningful step forward in a field that has advanced considerably since the landmark thrombectomy trials of 2016, and one that carries particular significance for UMC, the only Comprehensive Stroke Center in Orleans Parish, located in a region where stroke rates significantly exceed the national average. Young Lee, MD, cerebrovascular neurosurgeon at UMC New Orleans, was the first physician in the United States to perform a stroke thrombectomy using THUNDERBOLT. With nearly a decade of experience in stroke intervention, Lee has watched the field evolve from stent retriever-first approaches to aspiration-dominant workflows, and sees THUNDERBOLT as a meaningful addition to that trajectory.

In a new iteration of NeuroVoices, Lee walked through how his team adopted the technology, what happened during those first cases, how THUNDERBOLT compares to conventional aspiration, and what he believes it signals about where stroke intervention is headed, including the still-unresolved challenge of medium and distal vessel occlusions.

NeurologyLive: UMC was among the first in the country to use the THUNDERBOLT procedure. Walk us through how you incorporated it and how those first cases went.

Young Lee, MD: Stroke intervention is focused on removing the clot as safely, quickly, and efficiently as possible. We have a great relationship with Penumbra, so we were able to get the THUNDERBOLT technology pretty much as soon as it was FDA cleared and available. We had it on order, and we had it the next day essentially. The first stroke case came about within a week of us having the device.

The workflow is quite similar to aspirating with a constant suction device. The device uses modulated aspiration instead of constant suction, using computer algorithms, AI essentially, to modulate the aspiration to fatigue the clot and achieve complete clot ingestion. When we try to suck out the clot using old methods, typically the clot gets corked to the end of the catheter, and you end up pulling the catheter through the guide catheter to remove it. With this device, the aim is to break the clot up and suck it into the catheter completely without having to remove the catheter.

Our first cases were actually quite difficult. The first case had a history of intracranial atherosclerotic disease with an M1 clot that turned out to extend into both M2s. The THUNDERBOLT really helped us get that M1 clot out and allowed us to then access the M2 clot, and we achieved a TICI 3 reperfusion. The second case was also an M2, a medium vessel occlusion, and we achieved a TICI 2c reperfusion.

What advantages does this approach offer compared to what we have traditionally had?

In the past the assumption was very simple: blood vessel, clot, suck the clot out. As we've done more of these procedures over the last 10 years since the landmark trials in 2016, we've come to realize that clots are not homogenous. There are various different types. Some are more fibrous, some might have calcium inside, some are soft. A single approach not tailored to the specific clot type tends not to work well for certain clots, like those in intracranial atherosclerotic disease.

With THUNDERBOLT, the computer detects the clot, fatigues it, and then tries to suck it completely into the catheter. In my head, it's almost like doing multiple passes several times a second because you're sucking, releasing, sucking, and the computer is modulating that based on how it's perceiving the clot is being pulled in. That's one big advantage.

The other big advantage is that once complete clot ingestion happens, you can actually see it. The catheter that was corked and not flowing before will suddenly show blood flowing, and that happens more often than not in my experience with THUNDERBOLT. You don't need to pull the catheter out to go after more clot. Once it's sucked in, you can inject through the guide catheter, see what's more distal, and just advance the catheter. You save time, you're less likely to injure the vessel, and the workflow is essentially the same as using a constant aspiration catheter with just an additional device attached to the machine.

What safety considerations go into this, and what lessons would you share with other clinicians?

One of the most important things is having Penumbra representatives there with the device. I believe the company is essentially requiring that for your first few cases, and I think it's essential. The workflow is the same, but there is an additional device, and you want them there to help your techs so the workflow goes smoothly without any delays.

From a patient safety standpoint, we're using the same reperfusion catheters as before, so whatever you were doing to stay safe in the past, do the same thing. Also understand that you don't have to pull the catheter out each time. If you get complete clot ingestion, don't pull it, because in my opinion that can increase the risk of embolization to new territories. You can do an injection around the guide catheter and assess distally. Pay attention to what the machine is telling you, and the Penumbra reps will help you interpret that. And if the computer-modulated aspiration isn't working for some reason, the machine can also do continuous aspiration, so you're not losing out on what you already had.

How does THUNDERBOLT fit into the broader momentum in the stroke field right now?

I'll take you back to when I was starting residency in 2016, when those landmark trials came out. They were all focused around stent retrievers, and if you were doing a thrombectomy with evidence behind it, you would have done a stent retriever case first line. Obviously, that's changed. Most endovascular neurosurgeons, neurologists, and radiologists now use aspiration first, and we know that from surveys. It's because it's safer. The stent retriever isn't scratching the inside of the vessel as it comes out. THUNDERBOLT is just adding to that. Now you're less likely to need four or five passes. You can sometimes achieve the equivalent of five passes in one or two, which is a huge advantage.

One of the disappointing areas has been medium and distal vessel occlusions. We've had three big negative trials, ESCAPE-MeVO, DISTAL, and DISCOUNT. The ORIENTAL-MeVO trial out of China this year showed positive results, but it may not be generalizable to the U.S. population. The biggest question is whether there is some sort of technology deficit that's not allowing us to safely address medium to distal vessel occlusions.

Penumbra is running the FORWARD study, enrolling around 250 patients at 40 sites, looking at whether their reperfusion catheters can achieve meaningful reperfusion in M2 occlusions. That's where the stroke field is moving. And then the other big unaddressed need is how do you treat clots in intracranial atherosclerotic disease, which is very frustrating with the re-occlusions.

For our clinical audience, give a breakdown of the FORWARD study and its significance.

The initial study for the THUNDERBOLT system was the THUNDER study, which is already complete and showed good results for first pass with minimal complications compared to prior studies. The FORWARD study is enrolling up to 250 patients at 40 sites, looking at Penumbra's reperfusion catheters, the ones used with THUNDERBOLT, which come in various sizes.

The target is to see how well they address M2 occlusions, and in my mind, it's trying to provide evidence that there's hope for medium to distal vessel occlusions. We want to see fewer passes and less vessel injury, and medium vessels are smaller and more fragile, so they're more susceptible to that kind of injury. I'm glad to see Penumbra trying to address whether this works in those vessels.

Are there other stroke types or scenarios where you'd like to see THUNDERBOLT explored further?

THUNDERBOLT started in peripheral intervention before it was cleared for neuro interventional radiology. Something that comes to mind for me is severe cerebral sinus venous thrombosis. Anticoagulation alone is often not enough in severe cases, especially when the patient is comatose or quite neurologically impaired.

One of the challenges in neuro IR is that we're not as familiar with larger catheters going into the venous sinuses to suck those clots out, and there's a lot of clot in those veins. I know this is off-label, but if we could take a catheter into those cases and achieve complete clot ingestion, we wouldn't have to pass it a thousand times. I'm interested in exploring that because there's not a good answer for it right now.

Transcript edited for clarity. Click here for more iterations of NeuroVoices.