Early Data on Temporary Spur in BTK PAD Show Efficacy, Limited Recoil

LEIPZIG, Germany—New technology that involves placing a temporary spiky scaffold in the artery is showing promise for overcoming some of the most common limitations of drug-coated balloons (DCBs) and drug-eluting stents in the treatment of challenging below-the-knee (BTK) chronic limb-threatening ischemia (CLTI), according to interim results and a recoil substudy from the DEEPER OUS trial.

Among the challenges that BTK lesions pose are severe calcification and elastic recoil, both of which create issues with drug uptake in the arterial wall, noted Michael Lichtenberg, MD (Vascular Centre Clinic Arnsberg, Germany), in his presentation here at LINC 2023.

The Spur stent system (Reflow Medical) is a temporary self-expanding mechanical scaffold containing radial spikes on a sheathed delivery system. It creates small channels that penetrate the vessel wall and may optimize drug delivery when used in conjunction with a DCB. The device is drug-agnostic, so it can be used with any available DCB. In DEEPER OUS, it is being used with eight different brands of commercialized DCBs available in Europe.

The trial of 107 highly comorbid BTK patients from 10 centers in Europe and New Zealand met its primary endpoint, with 87.7% of patients in the per-protocol analysis having primary patency of treated lesions at 6 months on ultrasound, with 85.7% in the modified intent-to-treat analysis. No safety events occurred related to either the device or the procedure.

Patients will be followed out to 5 years and while it is still early to draw conclusions, Lichtenberg said, it appears to be a “very good option” for the treatment of BTK disease “in our very sick patients.”

Thomas Zeller, MD, PhD (Universitäts-Herzzentrum Freiburg-Bad Krozingen, Germany), presented the substudy on vessel recoil, which refers to the physical reaction of the vessel after dilatation that causes the lumen to narrow. Some studies suggest that vessel recoil is more common in diabetic patients, who make up a large proportion of those undergoing peripheral interventions. Diabetic patients account for nearly 70% of the DEEPER OUS cohort.

“Vessel recoil is one of the limitations of below-the-knee interventions, [and] it may contribute to restenosis,” Zeller noted in his presentation. “We have so far no published long-term data about infrapopliteal relevance of vessel recoil.”

The substudy sought to evaluate recoil at 15 minutes after the Spur stent was activated, defining it as a greater than 10% reduction in lumen diameter as seen on angiogram. “The substudy showed that the bare temporary Spur stent system reduced vessel recoil by more than 50%, whereas previously recoil rates of almost 100% had been reported,” Zeller said.

The 100% figure refers to data from one of the few studies to look specifically at recoil that found that the mean luminal compromise when recoil occurred was 29%.

Commenting for TCTMD, Sahil Parikh, MD (NewYork-Presbyterian/Columbia University Irving Medical Center, New York, NY), said the findings are interesting but need to be fleshed out with larger patient numbers.

“The amount of recoil that we see with balloon angioplasty is not well understood. The truth is you could probably get recoil out to 24 hours or maybe even longer, but we think most of it happens in the acute phase,” he added. “Their technology may have some advantages at preventing recoil [but] it’s too early to tell.”

Main Trial and Substudy Results

Patients in DEEPER-OUS had a mean age of 76 years, and 22% were female. Diabetes was present in 62% and hypertension in 94%. The trial enrolled patients with lesion lengths up to 150 mm and a total treated length of up to 240 mm. The mean treated length was 92.7 mm. Approximately 20% of patients had level 3 calcification and all were Rutherford category 3-5. There were also high rates of chronic kidney disease and prior amputation.

All patients met the primary safety endpoint of freedom from device- and procedure-related death through 30 days in both the per-protocol and modified intent-to-treat analysis.

Looking at secondary endpoints, Lichtenberg noted that freedom from clinically driven TLR at 6 months was 92.6%. Rutherford score improvement was seen at 3 and 6 months, improving from a mean baseline score of 4.5 to 2.1 by 6 months (P < 0.0001). Among those with Rutherford class 5, the mean wound size decreased from 1,701 mm³ at baseline to 136 mm³ at 6 months (P < 0.005). The rate of freedom from major amputation was 99%, with 100% of the cohort free from target-limb major adverse event limb events (MALEs) and all-cause perioperative death.

Zeller said the overall percentage of recoil was 42.5%.

“The presence of recoil was almost evenly distributed between lesions with no calcification, mild-to-moderate, and severe calcification,” he added.

In terms of patency related to calcification, even in moderate-to-severe lesions the patency was 100% at 6 months, which Zeller acknowledged is “probably not reality,” given the small numbers in the trial.

“But it tells us that if you use the Spur system with severely calcified lesions, number one, we don't see more recoil, which we could expect in severely calcified lesions after Spur treatment,” he said. “And we see an excellent patency over time.”

As to whether the technology actually promotes drug delivery to the peripheral vessels, “the short answer is nobody knows,” Parikh noted. “Obviously the promise of this would be to use it as a lesion prep tool. This is nonpermanent so you’re not leaving a scaffold behind.”