Laser Atherectomy in Practice: Clinical Data & Procedure Pearls

[Dr. Chris Beck]
Actually, this is a perfect shoehorn into talking about the Pathfinder data. Will you talk about the study, what it was set up for? Set the scene for the study, what were the goals, and, ultimately, what were the results?

[Dr. Tony Das]
Sure. It was a prospective study. It was single-armed, multi-center. I think there were 10 centers in total. Open label. It was a registry.

[Dr. Chris Beck]
Were you guys a center?

[Dr. Tony Das]
We were, yes. What we wanted to accomplish is safety and efficacy. Efficacy essentially was the idea that you finish the procedure, including the laser and any adjunctive therapy that you wanted to use with a less than 30% residual. Then, the safety was that you had no major adverse limb events or major adverse events in the actual time frame of the procedure. Death, lower extremity amputation, and all the usual things that you would think about.

102 patients were enrolled. Typical demographics that you would think for vascular patients. 121 lesions were treated. Essentially, the lesions were in that 15-centimeter range, relatively typical, long-length lesions. They were Rutherford categories 2 through 5, excluding the 6s and excluding the 1s. Essentially, it met its endpoints. Safety and efficacy in those patients.

We can go over the numbers in more detail, but essentially, it was to take a look at a laser that was very different from the ones that we're used to. The reason I want to emphasize that is because even though the wavelength was in the same neighborhood, 355 versus 308, this is a solid-state laser, which means it uses not those noble gases like the Excimer laser does, but it uses solid-state crystals. It's a very stable type of device, and it's a simple plug-in, 110-volt plug-in. You don't have to use the more complex equipment. It's a smaller, more nimble, unit because it doesn't have to enclose those gases inside of the actual zamboni, that we call it. I think it's a little bit different than the Excimer laser that we're typically used to. Although we use the word laser generically, there's some specifics. They do work very differently. I think that the idea here was, is this very unique laser science, is it safe and is it efficacious in these patients? It turned out that it really was.

[Dr. Chris Beck]
Let's just start with safety. How safe was it?

[Dr. Tony Das]
95% of the patients had no untoward events after the procedure, and that includes the big things that we talked about: death, lower extremity amputation, et cetera. In that setting, we would think that there would be things like distal embolization requiring a surgery, all those things, but that happened less than 5% of the time in a very broad category of patients. Safety was certainly met.

[Dr. Chris Beck]
I did look over the paper. One thing that did strike me was that, at least for the demographics, it's not like chip shots were chosen. I feel like the demographics were really what you might see in any robust peripheral arterial practice. It wasn't just set up for the short segment, 70% SFA or stenosis. You had long segments. You also had relatively well represented as far as severity of disease. Was that intentional? Is that just what you could enroll and otherwise enrollment would just take too long?

[Dr. Tony Das]
If you think about it, one of the things that's a beauty of registries is that they're real world. Here's a situation in which you can't really cherry-pick the lesions if you want to enroll into the trial. The demographics are essentially what you would expect. Mostly males, I think 70% were males, 40% were females. There was some diversity in this overall population, not as much as we'd like to see, but there definitely was. Then, all the usual comorbidities; people had 50% had coronary disease, hypertension, hyperlipidemia, et cetera. If you look at the Rutherford categories that were 3, 4, and 5, that was 88% of the patients. Very few were Rutherford 2, which was only 5%. Even though they were included, it was a minority of the patients. These patients had pretty significant low-performing, walking questionnaire scores. Less than 39% low-performing patients in the majority of the patients, 82% of them had that.

Pretty important. You were describing the lesions. These lesions were either de novo or restenotic. Most of them were de novo lesions, about 70%, and restenotic lesions about 17%. They were relatively long. These were lesions that were an average of 14 centimeters length and then they went up to 40-centimeters length overall size and length. This was not a cherry-picked type of registry at all, just like you mentioned.

[Dr. Chris Beck]
We talked about safety. Efficacy- How does it do?

[Dr. Tony Das]
In all the subject patients, almost 70% of these patients reached the efficacy of less than 30% at the time of the procedure. That included the adjunctive therapies. What's super interesting is that at the 6-month and 12-month timeframes, it actually remained at that amount of patency as well. That's the part that was interesting to me. If you look at the ABIs at baseline 6-months and 12-months, they improved over time. You look at the ABI and TBIs. If you look at the walking questionnaires, they all tend to stay good over time. In addition to that, the patency rates also stayed quite good. If you look at the initial amount, it was 70%. Then at 6 months and 12 months, the number of patients that were occlusive were in the 10 to 15% range, which means that they actually stayed open over this period of time, which is very unusual for long lesions like this.

[Dr. Chris Beck]
I just want to ask, if you had to give some advice to someone who's just starting out their practice, whether it's hospital based or OBL based, and they've read the paper or in training, they liked using a couple different atherectomy dice included, which is laser, what advice could you give them about building an atherectomy program around laser? What would you say? "Hey, this is what you need to have. This is the things you need to think about." Just advice you might give like a young colleague.

[Dr. Tony Das]
Sure. It's a good question. I think for the most part, being too prescriptive is a little tricky. On the other hand, you need ablative technology in the OBL and ASC because it's what you have in the hospital outpatient department. You cannot be without. It's nice to have a system that does ablative therapy as well as thrombus removal, like for instance, the Auryon laser does. That is an advantage that I think that I would definitely consider. If I was just counseling somebody on what they should have, they should have a laser and they should have one calcium ablative technology in the outpatient lab. Those two things would get you through 99% of the lesions that you're going to deal with.

[Dr. Chris Beck]
I hope that people heard that because sometimes it's like paralysis analysis. You have so much at your disposal and then each device has its own research associated with it. Sometimes it's nice to know that, breaking the two broad categories, you can have this and you can have that. That's going to get you through greater than 90% of the cases that will come at you.

Another question in that vein. Someone who's a little bit further along and is looking to dig a little bit more into the data behind laser atherectomy. Do you have some recommendations or resources that you could recommend to them? Like, "Hey, look, these are the papers that are going to talk about this stuff, and talk about ways you can counsel your patients or talk about outcomes that you can expect.” Basically, the papers that let if you're on the right track?

[Dr. Tony Das]
I think there's a fair number. If you go back to the Spectrometrics laser data, it started with LACI, which was a laser atherectomy for critical limb ischemia patients. Essentially, in those papers, we were looking at whether patients would benefit from a reduction in amputation. If you look at that, it was a significant benefit for adding laser into those patients.

Then, it led to two other sets of papers, including the SFA in-stent restenosis Excimer laser trials. Those showed that laser, in addition to balloon angioplasty, unfortunately, at that time, we didn't have any drug-eluting balloons, did improve. The problem there is that the long-term restenosis rate was still quite high. We did a trial using cryoplasty and laser and showed that in that trial that there was a significant reduction in patients that were diabetic in greater than 20-centimeter long lesions and the restenosis rates were almost halved in the secondary restenosis in the cryoplasty trial.

Then, if you go back even further, if you look at the long laser trials that were done with Giancarlo, Biamino, and some of the real pioneers in that space, those trials suggested that there were so many different adjunctive therapies that you couldn't really tell what the laser really did in those. I said, back to laser has a little bit more religion sometimes than science, but it definitely works. If we go into the physics of it, you can see why I think it does. Certainly, the experience we've had in thousands of laser cases over the years is that it changes the compliance, it reduces the stent use, it decreases the likelihood of distal embolization, and it enhances the thrombus removal and uncovers the lesion. If you want those things in your procedure, you probably want to think about using it.