Fixing Femoral Flow with Percutaneous Transmural Arterial Bypass (PTAB)

[Dr. Sabeen Dhand]
Let's focus our work on endo and peripheral vascular disease. We know, I mean, we've been there where these lesions can be very, very tough to tackle. They're a long segment and you're battling wires from above and below. Let's talk about the Detour System. What is it?

[Dr. Sean Lyden]
The easiest way to think of the Detour System is it's a way to create a percutaneous femoral to popliteal bypass. You're going to start in the arterial side, you need basically just enough opening in the origin of the SFA to get a catheter or wire in at least 3 centimeters. Then it uses a spring loading proprietary crossing device which will puncture out of the superficial femoral artery into the femoral vein, and then travel down the femoral vein, and then use that same crossing device to cross back from the femoral vein into the popliteal artery. Then you're basically lining that segment with a PTFE stent graft, usually two or three stent grafts to cover that segment.

[Dr. Sabeen Dhand]
They use this terminology as acronym, PTAB, what does that stand for?

[Dr. Sean Lyden]
That's an acronym that Endologix came up to really to suggest that this is a therapy, so percutaneous arterial bypass. It's really instead of thinking about it's just an endovascular solution, you're really trying to create a endovascular bypass, more akin to what we would be doing if we were doing a femoral popliteal PTFE bypass.

[Dr. Sabeen Dhand]
Sure. I'll tell you what my first impression when I heard about that. What did you think when the company came to you or you heard about Detour? What did you think?

[Dr. Sean Lyden]
Fortunately, I've known about it from the very beginning. It came as an idea by Jim Joy. I'm one of the board members for VIVA. Jim was a fellow board member and Jim sat at one board meeting talking about this crazy idea he'd come up with and that he was using off-the-shelf devices and patients that he treated endovascular with multiple failures to now go outside of the artery into the vein and then reline the entire system. When he first told me about it, I thought he was absolutely crazy.

I'm like, "Why would you ever do that?" Then watching him then create a startup and say, "Hey, it seems like we can actually create a unique device and a unique covered stent." Then he came to me, said, "Hey, would you be interested in helping leading this clinical trial?" The one thing I know from my 22 years of being a vascular surgeon is that if you think that endovascular will not eventually find a solution to replicate and improve on what we could do surgically, you're completely wrong, and so when the opportunity came up, I was happy to jump on it.

[Dr. Sabeen Dhand]
You did already talk a little bit about devices, but let's go a little bit more in detail. What's access like? Is it a six French access up and over when you're doing these cases because you want to target the proximal SFA?

[Dr. Sean Lyden]
Currently the crossing system requires an eight French system, so you're going to have an eight French crossover sheath come from the contralateral common femoral, and then you're going to need venous access on the ipsilateral side most commonly coming in the posterior tibial vein with the six French sheath and just using a commercial snare.

[Dr. Sabeen Dhand]
Is it easy to direct the spring-loaded system towards the snare? Is it all just fluoroscopic? Do you need to use any ultrasound guidance or?

[Dr. Sean Lyden]
When the trial began, we did do CT scans, and I think for the people that had not done venous harvesting of the femoral vein or had any idea of where the femoral vein sat in relation to the superficial femoral artery it was very helpful, but for the most part, once you get venous access in the cap and advance a wire all the way up to the femoral vein near the common femoral vein junction, you're just going to put a commercial either single-loop or tri-loop snare, and so you have a target because you can fluoroscopically visualize it. Then the crossing device has markers on it to figure out which direction it's pointing, and then you can then get the two structures superimposed on top of each other and then fire the crossing device.

[Dr. Sabeen Dhand]
Got it. Then what size are these stents that you're putting from the proximal SFA down into the popliteal artery?

[Dr. Sean Lyden]
When the trial began and now that it's got FDA approved, the stents are really limited to three different diameters, and so they are up to 7 millimeters in diameter. You can treat an artery that goes between 4.5 and 6.7, so they have three different diameters currently with their current offering.

[Dr. Sabeen Dhand]
Are you sizing these arteries with IVUS at all as far as what the proximal SFA is looking at or what the distal popliteal is looking like?

[Dr. Sean Lyden]
It can be done with either CT, IVUS, or angiography. I am fortunate that in where I work, we were given a gift from the Koch company, from Bill Koch and we have a CT scan right in the office, so when the trial began using CTs for lengths and sizing, anybody that it's not going to be a contraindication to give them that the small amount of dye to get a CT scan, I still prefer to get a CT scan. I think you get great both length and diameter measurements. Then I tend to use IVUS very liberally. I found IVUS is much more accurate than angiography, so if I'm not using CT, I'm using IVUS.

[Dr. Sabeen Dhand]
Perfect. What is the furthest distal on the pop you can go back for the second anastomosis, essentially?

[Dr. Sean Lyden]
Correct. for the trial, you had to have at least one vessel patent runoff, and you had to land at least 3 centimeters above the tibial plateau.

[Dr. Sabeen Dhand]
Okay, so above knee. Any below the knee pop usage you've done?

[Dr. Sean Lyden]
You had to land there, so it ends up being sort of right behind the knee. The way I look at it, most of them ended right somewhere in the midpoint of the patella.

[Dr. Sabeen Dhand]
Have you done any cases that are technically below pop just because the lesion was too long in the fem-pop?

[Dr. Sean Lyden]
No. The trial itself didn't allow that. Like I said, you had to land with 3 centimeters above the tibial plateau, and it just got FDA approval in May of 2023, and I'm excited that we have our first case actually this Friday at Cleveland Clinic.

[Dr. Sabeen Dhand]
Oh, that's awesome. The big elephant in the room, and I think my first impression when I heard about the device is like, "How are you not causing obstruction of flow in the femoral vein and how are you not increasing the risk of DVT?" Tell us more about that.

[Dr. Sean Lyden]
That was one of my concerns as well. Fortunately, being part of the trial and discussions with the FDA, there was a lot of safety things built into the trial to evaluate that. The first thing was you either had to have a duplicated femoral vein or you had to have a femoral vein that had at least a 10-millimeter diameter, and so if the largest device is seven, you're still going to have some flow around the femoral vein. In my surgical practice, I use the femoral vein a lot for infected devices, infected aortas, and infected other things, so I know you can take the femoral vein without really any significant consequence to patients, but the big concern was both DVTs and PEs. We just reported the two-year data at the Society for Vascular Surgery Vascular Annual Meeting in May of 2023, and the rate has been really low at 4% for DVT, and there's not been any pulmonary embolisms in the trial. It's really borne out that this does not cause a lot of long-term issues.

[Dr. Sabeen Dhand]
Totally. It's pretty amazing when you think about it. There's a 7-millimeter potentially stent that's sitting in the vein and not causing DVT. Are you putting these patients-- are they anticoagulated as far as medical therapies?

[Dr. Sean Lyden]
The trial required aspirin and Plavix throughout the duration of the trial, but when the trial began, we would have never guessed, but the VOYAGER and the COMPASS trial came out during the trial, which showed that if you're on a direct oral anticoagulant, you have lowered acute limb ischemia events, and so a lot of the investigators wanted to try those in our patients. We really then said you could modify from aspirin and Plavix using rivaroxaban or some of the other direct oral anticoagulants as standard care, and so that was allowed within the trial, and so if patients wanted to be on it or they had some other reason to be on anticoagulation, it was okay.

[Dr. Sabeen Dhand]
What about if they had a history of DVT or anything, was that a contraindication?

[Dr. Sean Lyden]
Exactly. When the trial began, if they had-- they had to have ultrasound to evaluate their ipsilateral vein, but if they had a history of a DVT or did not have an adequate sized ipsilateral femoral vein or a duplicate vein, they could not be enrolled on the trial.

[Dr. Sabeen Dhand]
How steep was the learning curve when you first started from the beginning?

[Dr. Sean Lyden]
It's really not. One of the things we did, because you need to have both arterial access and venous access and we're a big department, we said that we would have more than one physician doing the case, even though we're a training institution and you have trainees, sometimes having a staff physician who knows what they're doing is much, much easier. Our very first case took an hour and 20 minutes. I think the two things that provide a little issue for some people is if you don't do a lot of venous interventions or you're not used to using ultrasound guided access yourself, the hardest part, I think the learning curve of the trial for many of the investigators was getting a percutaneous posterior tibial vein stick, and so that took longer than most of the case for everybody.

[Dr. Sabeen Dhand]
What about how fast does the case now on average take you? The first one, an hour and a half, what are the–

[Dr. Sean Lyden]
They basically took about that period of time. The trial required a complete leg runoff before the procedure, after the procedure. It also required treatment of inflow of iliacs, which was okay. If you look at total procedural time, I don't think it reflects what it's going to take now it's FDA approved and commercial because I typically would get a CT scan ahead of time, and if their inflow is good, I'm not going to treat it at the time, I'm not going to get all those extra pictures because we don't get paid for it, and if you already have some other way of imaging it, it's completely unnecessary.

I can imagine that once it's commercial approved that it's probably going to take people somewhere between an hour or two. Probably most of the patients were done with local anesthesia, but some were done with general anesthesia. At our institution, the very first one we did it under general anesthesia, not because the patient needed it, but I always find when you're doing a new device and it's a new trial, you want to be perfect and you want to be able to talk openly amongst the team-

[Dr. Sabeen Dhand]
Exactly right.

[Dr. Sean Lyden]
-about your plan so it goes best for the patient. Whereas sometimes it's a little harder with an awake patient who's asking what's going on while you're doing it. They don't understand.

[Dr. Sabeen Dhand]
They're like, "Why are you asking how to do this?" [laughs]

[Dr. Sean Lyden]
Exactly. With the crossing device, all crossing devices where it's the commercial Outback or the Pioneer or this crossing device, the EndoCross, they'll have their hieroglyphic you have to look at to know which direction the crossing device is aiming at, and so in the room, we'd have these big posters of what it looks like everybody agreeing that, "Okay, we all agree this is the direction we're pointing," because I sort of look, it's like carpentry, can measure a bunch of times, but you only get cut once, and so if you're firing the crossing device, you ideally want to make sure everybody's on the same page. "We're heading where we think we are and get it across the first fire every time."

[Dr. Sabeen Dhand]
Speaking of the crossing device, it must have a longer needle than Outback or Pioneer, right?

[Dr. Sean Lyden]
It does, and it's also spring-loaded.

[Dr. Sabeen Dhand]
Spring-loaded, it's a very like quick jab.

[Dr. Sean Lyden]
Yes. You basically, you cock load the spring and it throws out, don't quote me on this, but I think it's 15 millimeters. I always tell people, when you play with the device, be very, very careful because when they're showing it to you and we showed it to sites and we had training, if someone were to push the fire, it'll go right through your entire finger. Yes. It will cross a stent. It'll cross calcium. I have to tell you, I'm excited for it to be approved because I can see all the other anatomies that I'm now going to want to use this device because for Iliacs-

[Dr. Sabeen Dhand]
It sounds awesome. That's exactly what I was saying. I was like, okay.

[Dr. Sean Lyden]
-venus interventions. I've already thought about all the different anatomies that because this thing, the Outback, you're pushing really hard with your finger, and if you can't push hard enough, it doesn't cross, same way with the Pioneer, where this thing just, it's like a gun, it comes out so fast.

[Dr. Sabeen Dhand]
That's amazing. You said that the device now it's FDA approved as of last month or a month and a half ago. Is it now available? Any site can get it?

[Dr. Sean Lyden]
It should be soon. From what I am told by Endologix, I think we will be the first US case. The trial we did in the United States was called the Detour 2 trial. It was preceded by in Europe, the Detour 1 trial. In Poland and Latvia, they had the most experience and they've been using this device as part of their practice for three and five years now at some of the sites.

[Dr. Sabeen Dhand]
That's amazing.

[Dr. Sean Lyden]
US, it's ready now, but I don't think anybody's gotten to use it yet.