The Advantages of Auryon Laser Atherectomy in Calcified Arteries

[Dr. John Rundback]
Well, let me step back even before that, because the aha moment, maybe it occurred a year or two earlier. When we brought over the Eximo platform, which was the Israeli platform, which is now the Auryon laser, which was purchased by AngioDynamics, I had been the international and principal investigator for that IDE study. We had a fair amount of calcium in that study, I believe 40% of patients had moderate to severe calcium. We also had other kind of plaque morphologies. We noticed a couple of interesting things. First of all, in both the IDE study and the subsequent registry, some patients get a DCB after atherectomy and angioplasty, some didn't. Some patients had calcium, some didn't. Our observation when we interpreted the data that there didn't seem to be a whole lot of difference in clinical outcomes at six months and a year in terms of restenosis, and obviously events, in patients who had DCB or didn't, and patients who had moderate to severe calcium versus lesser degree of calcium. That was sort of an aha moment there. Are we using this laser in a way, maybe it's not specific to this particular laser, but we think it is, that is obtaining a different result than we would have anticipated with other modes of atherectomy?

That was the first aha moment. Now, the next remarkable thing is we went back to AngioDynamics and said, "This looks a little bit different. We need to do some preclinical work. Would you support that?"

[Dr. Sabeen Dhand]
It's a big ask.

[Dr. John Rundback]
Right. It's a big ask. That's always a little bit of an iffy proposition because in general, especially when you've had fairly favorable results, companies are a little hesitant to open up the lid a little bit, look under the trunk and–

[Dr. Sabeen Dhand]
They already know it's working. Let's not rough the feathers, basically.

[Dr. Sabeen Dhand]
Interesting.

I want to kind of pull it back. Probably no one has access to a micro-CT in their lab. Guarantee no one who's listening on this podcast has that or can see this plate-like calcification, medial, et cetera. Coming back to a practical standpoint, one is, with your findings of using a laser and other atherectomy devices, do you need to make a difference between intimal and medial and decide on your atherectomy device based on that? To do that, would you use IVUS or what would you do?

[Dr. John Rundback]

This is not an IVUS podcast, but we use IVUS in almost every case. Obviously a lot of reasons to use IVUS, make sure you're intraluminal, first of all. Atherectomy is a very different value proposition if you're sub-intimal, although we do use it in selected cases if there's calcium to get an idea obviously of vessel size and determine calcium.

Absolutely. When we see patients who have a lot of calcium, now we're looking at calcium dedicated technologies, which might be orbital atherectomy or now based upon this data, it might be more Auryon or other forms of laser atherectomy. If we see a lot of intimal calcium and really just complete shadowing, like you said, now we're leaning more towards orbital atherectomy. Now we have to get that inner surface before we can ever have an impact. If we see deeper calcium, deep to the internal elastic lamina, that gray ring on IVUS, now those are ideal cases based upon our findings for this technology. What you said is exactly right. We did this study with an idea to finding a clinical implication. This wasn't just done in isolation.

The idea was how can we learn from this so that we could guide clinicians on what to do? That's exactly the point that we came up with. If you have a patient and you see this calcium and it's not predominantly intimal and circumferential calcium, that's a case that you want to make sure you go super slow so you deliver energy. B, you want to make sure you make a pass at least 60 millijoules so that you can treat that appropriately.

[Dr. Sabeen Dhand]
A follow-up question to that too, why not just turn up the energy all the way? What does the energy go up to above 60? Can it go to 80?

[Dr. John Rundback]
No, there's two settings, 50 and 60. The reason that we don't necessarily do that is that the unique thing about the Auryon laser, since it's a very, very short pulse width and it's delivering these bursts of energy is that it's actually on a fraction of the time. Because it's on a fraction of the time, there's a large amount of time for tissue cooling. So the predominant effect is photo-mechanical and not photo-thermal, because as you know, thermal injury has its own long-term impact on producing restenosis. That's why we generally start low. By starting low, you're avoiding thermal injury. If you need to then you can go a little bit higher, certainly if you want to maybe get a larger lumen, but when you have calcium, you need to use the 60.

[Dr. Sabeen Dhand]
Again, I'm more familiar with the Spectranetics/Phillips laser where that had different settings as two different numbers where you can go up to even 80. Now, how does that compare? Is it still doing the jackhammer effect you're talking about and delivering energy in a photo-mechanical way to the medial and maybe even other adventitial or intimal layers?

[Dr. John Rundback]
Yes, obviously you have the frequency and the fluence that you're adjusting on the Phillips laser. The fluence is basically the size of the micro bubble at the end, and the frequency is going to be the mechanical effect of that. Either way, the pulse width on that laser is more in the order of 100, or even more, I think it's even more than that, nanoseconds. Whereas the pulse width on the Auryon laser is 10 nanoseconds.

There's going to be much, much more thermal delivery with that. Yes, you can dial it up, but by dialing it up, you're actually getting a lot of thermal energy delivered into the vessel wall, in theory. Again, a lot of this is kind of in theory. It's hard to test this specifically. You can't put a little temperature probe, but–

[Dr. Sabeen Dhand]
You can put it in your bottle with the gel.

[Dr. John Rundback]
Right, exactly.

[Dr. Sabeen Dhand]
Give it a try. No, it's very interesting. I'll be honest, in my practice, where we have a ton of tibial disease, a ton of calcium, I've always been under the impression of, if I'm doing atherectomy, my first thing is CSI. I think CSI, orbital atherectomy is my go-to because I have been so disappointed with other technologies with heavy calcium in the tibials. It's a tough thing. I've always asked my friends, Kumar, all these other people, Mark, Mike Watts, do you guys use laser and stuff? They'll say yes, and then I'll try the laser that I'm familiar with, and it just didn't work. That's why I always go back to orbital atherectomy.