Michael Conte, MD, recently used his 2024 Veith Lecture to call on young vascular surgeons on the peripheral arterial disease (PAD) frontlines to drive the space forward amid a great unmet need.
The professor and chief of vascular and endovascular surgery at the University of California San Francisco (UCSF) called on those in the vascular surgical specialty to take the lead in confronting the challenges of the global PAD burden and in furthering the science. He laid down the gauntlet. But many are already answering the call. And some have already been chosen.
One of those pressing at the leading edges of the PAD frontier is Trisha Roy, MD. The University of Toronto, Ontario, Canada-trained vascular surgeon-scientist recently received a $3.3 million funding boost from the National Institutes of Health (NIH) to push on with a cutting-edge imaging technique aimed at pinpointing who benefits from an open bypass vs. endovascular intervention, as well as more accurately tailoring device selection.
Now based at Houston Methodist DeBakey Heart & Vascular Center, Roy is deep in the throes of developing a magnetic resonance imaging (MRI)-histology technique to help distinguish plaque morphology in PAD. As she puts it, the method is “unlike anything we have right now.” Establishing how hard or soft a plaque is via computed tomography (CT), X-ray or ultrasound is not possible, Roy explains. That makes figuring out whether an individual patient would be a good or bad candidate for an endovascular intervention on the same basis falls short. “If you have something that is a long, long, long occlusion but is very soft and easy to cross, you can’t tell that apart from a rock-hard dense collagen lesion with CT scans, X-ray or ultrasound right now,” she tells Vascular Specialist. “The only way we can test is by trying—and that is why we do endovascular-first for most of these patients.”
This raises a point of both challenge and excitement for Roy. Or, as Conte referred to it in his Veith Lecture at the 2024 Vascular Annual Meeting in Chicago: “opportunity.”
That endovascular-first approach was challenged by the landmark outcomes reported from the BEST-CLI trial. Key among its findings was that, for many patients with adequate saphenous vein, bypass surgery was a better option, Roy observes. High failure and immediate technical failure rates for endovascular interventions were reported. “The problem is that [bypass] is so much more invasive. So the question that we had with this NIH grant was: is it a matter of bypass being better for PAD patients full stop?”
Or, Roy considers, perhaps there is a way patients can be better selected for endovascular treatment. “We know that the most common mode of failure is the inability to cross a lesion because it’s too hard or too stiff.” Those immediate technical failure rates amount to about 15–20%. “We want to bring that down to 0% by selecting the right patients that you can treat.”
Which is really only the opening gambit in this MRI-histological quest.
“Once you get your wire across, how do you actually open the blood vessel in an effective way?” Roy continues. “We know that PAD plaques are very variable, and depending on what a plaque is made out of, it’s going to be more or less amenable to a certain device. Each of these devices are made for specific types of plaque. So, if you’re talking about something that’s a big nodular chunk of calcium, that’s going to be different from the eggshell calcium around the perimeter, which is different from soft thrombus, and so on.”
This brings to the fore an important biographical detail from Roy’s own trajectory—and how it interplayed with the development of the MRI technique.
She first started to work on the imaging modality as a PhD student in Canada. Back then, about a decade ago, Roy was more or less focused on the mechanical properties of plaques. Upon arriving in the U.S., the plethora of endovascular devices at the disposal of surgeons and interventionalists—unknown north of the border—helped drive exploration of the device-vessel wall-plaque morphology interaction. In essence, without the ability to differentiate different types of plaques, “we’re not able to make informed decisions about who’s going to benefit from what device,” she says. “So that’s why the mainstay, especially for below-the-knee disease, is still balloon angioplasty. And our results are dismal—up to 70% having re-narrowing within just three months.”
Another detail of the U.S. dimension, not available back home sans evidence in support of its use: atherectomy. “I come to the States and it’s used a ton here,” Roy observes. “I can see why—you know balloon angioplasty is not going to work; maybe atherectomy can help in some patients? We don’t know who or what, we say, ‘But let’s give it a try,’ as this is kind of their last chance.”
Cue the contemporary backdrop to atherectomy: overuse, questions of harm and worsening results, and mainstream media scrutiny. “We are looking at that right at the vessel wall level,” Roy points out. “We’re taking the legs of real patients who undergo amputation because we were not able to save their legs, characterizing those plaques, then using orbital atherectomy and comparing that with plain balloon angioplasty. We are making real observations of whether it helps in terms of the vessel wall damage, or are we still doing a lot of dissections? Or does it make any difference at all?”
Into the longer distance, Roy wants to see an outcome whereby a more precision level of care for PAD patients is achieved. “What I envision is that we are using MRI for patients we think need revascularization and individualizing our care based on what the patient’s individual anatomy is,” she explains. “I think that can reduce our failure rate—so, that 20% going down to 0%, but also ultimately making us more successful because we’re choosing the right devices for the right patients.”
The knowledge gleaned from the research thus far has also helped inform new device development. “Right now, we are using coronary devices and applying them to the leg,” says Roy, adding: “They haven’t been very effective.”
