Andrew Holden, Auckland, New Zealand, presented data for on the developments in bioresorbable technology yesterday. He said that, as drug-eluting balloon data are limited to short and intermediate length lesions, bioresorbable stents or scaffolds are an “exciting prospect” for the future.

He said that the long and mobile femoropopliteal arterial segment is a challenging environment for endovascular intervention; for more complex lesions a scaffold is often required to prevent residual stenosis and flow-limiting dissection. An anti-restenosis strategy is also important, particularly in claudicants where long-term patency is vital, he noted.

“Drug-eluting balloons are highly promising but have only been studied for any duration in relatively short lesions. Drug-eluting stents have shown satisfactory patencies in intermediate length lesions but suffer the problems of a permanent self-expanding metallic implant.”

Addressing this problem with drug-eluting stents, Holden said for many years bioresorbable stents have been eagerly awaited in the superficial femoral artery.

“A bioresorbable stent may provide a scaffold to optimise the acute result after angioplasty without the long-term irritation of a self-expanding stent. Such a scaffold must withstand the hostile environment of the superficial femoral artery, provide mechanical support and integrity through vessel healing, remain biocompatible through resorption and facilitate drug delivery,” he said.

Three bioresorbable stents have recently been studied in the superficial femoral artery. The Abbott Esprit 1 trial used a balloon expandable PLLA scaffold in iliac and femoral arterial lesions ≤50mm in length that could be treated by a single 6.0mmx58mm device. The study reported excellent procedural success. Although lesion length was short (mean 35.7mm), the patency data and improvement in Rutherford-Becker status at one year was very encouraging, Holden said.

The 480 Biomedical Stanza stent has been studied in the STANCE trial. This flexible, self-expanding stent is a PLGA and bioreorbable elastomer composite and fully resorbs in 12–15 months, according to Holden. Acute performance and subsequent stent strut encapsulation and resorption has been evaluated with optical coherence tomography (OCT). This study reported excellent procedural success and acute stent performance, treating longer lesions (up to 90mm).

Holden explained that late lumen loss seen in the first cohort of patients was due to a combination of vessel recoil and neointimal hyperplasia. The device was modified in a second patient cohort with minimal vessel recoil. A paclitaxel, drug-eluting version of the scaffold has recently entered the clinic in the SPRINT trial, he added.

Holden also reported that the Igaki-Tamai bioresorbable scaffold (Igaki Medical Planning) has been used in the superficial femoral artery in a 30 patient cohort. Acute procedural results were very good, as in the STANCE trial.

“Binary restenosis rates at 12 months were unacceptably high and further modifications are planned. Small clinician initiated trials using coronary bioresorbable stents in the tibial arteries are being performed but meaningful results are not yet available,” Holden commented.

“There has been considerable progress with bioresorbable stents in the superficial femoral artery. The technology is not yet ready for routine clinical practice but that exciting prospect should not be far away,” Holden concluded.

In his technical report of the Hybrid Vascular Graft (Gore) for the reconstruction of the superficial femoral artery, Jean Bismuth (Houston, USA) said the graft allowed a rapid sutureless anastomosis and was highly versatile in complex situations.

Bismuth reported that the graft is the first device that has been designed to “address the ever expanding number of hybrid operations, which combine both endovascular and open surgical techniques.” He explained that it was an expanded PTFE vascular prosthesis that had a constrained nitinol section and added that it “greatly expanded” the treatment options for dialysis access, aortic debranching, and arterial bypass procedures. Bismuth commented: “The graft allows the surgeon to minimise the invasiveness of a procedure all the while benefiting from the advantages of a bypass.”

He explained that although initially the graft was launched for arteriovenous dialysis access, it now had the same indications as “any vascular graft”. For example, at his centre, where the graft has been used in 150 cases, it has been used for “a good proportion of iliofemoral bypasses and a bunch of visceral debranching as well.”

Bismuth commented: “In the femoropopliteal segment, the Hybrid graft permits access through a smaller incision to an artery which is either hard to reach behind the knee or is diseased. The nitinol reinforced segment of the graft can be introduced through a less invasive access and can take advantage of the stent to treat a stenotic segment.”

As well as reviewing the advantages of the graft, Bismuth also discussed the “pearls for success” with the device and these included the fact that “imaging was key” to successfully accessing patient anatomy—“you have to know what you are going into”, he noted. Another pearl was that correct sizing was “essential” as he said that the graft should not be oversized by more than 20%. Bismuth added that he never oversized by more than 1mm and that correct sizing could mean that sutures were not needed at all. He explained: “Gore recommends a couple of patching sutures, but I have never put any in. It is a personal choice and I have never had an issue with needing to use sutures. It is all about the sizing. If you only upsize by 1mm, you are probably not going to have any problems.” Other tips for success included not completely inserting the nitinol reinforced segment into the artery, ensuring adequate outflow and inflow, and covering all of the disease in the artery.

Bismuth concluded: “Hybrid procedures are likely to be more prevalent; the Hybrid graft allows a rapid sutureless anastomosis, particularly for difficult sites and rapid bailout. It is highly versatile in complex cases.” 

Andrew Bradbury (Birmingham, UK) reported that a new randomised controlled trial, BASIL 2, has been launched because there is an “urgent need” to undertake pragmatic, scientifically robust and publically-funded randomised controlled trials of endovascular interventions in patients with severe limb ischaemia.

Bradbury stated that the findings of BASIL 1, which showed a significant improvement in overall survival with endovascular therapy in patients with severe limb ischaemia compared with surgery at 7.3 months (but not at two years), and those of other studies have been used to justify “an endovascular approach” in this group of patients. However, he added that BASIL 1 may no longer be relevant because of several changes in the treatment of severe limb ischaemia since the study was published. For example, Bradbury reported, endovascular therapy had “changed beyond recognition”, interventional radiologists were more skilled at performing endovascular therapy, and surgeons could now perform hybrid procedures. Furthermore, other studies in this area were industry sponsored and had not produced the answers needed to make nation-wide decisions about which therapy to use. Bradbury said, during development of guidelines for peripheral artery disease, the UK’s National Institute for Health and Care Excellence (NICE) were “shocked” that the day-to-day decisions for the management of severe limb ischaemia were being based on such a “lack of evidence”. 

Therefore, the BASIL 2 has been launched to provide more data on the effects of endovascular therapy compared with surgery in patients with severe limb ischaemia. Bradbury reported that in the superiority trial, 600 patients with below-the-knee or femoropopliteal atherosclerosis will be randomised to receive “best endovascular therapy” or a vein graft. He added that the recruitment process, which was due to start in a few weeks, would last for 36 months and the primary endpoint was the rate of amputation-free survival at 33 months. To show superiority of endovascular treatment, Bradbury reported, there needs to be a 15% difference in the primary endpoint between the groups.

The study will be funded by the National Institute for Health Research and, according to Bradbury, has received “overwhelming support” from both interventional radiologists and vascular surgeons. He acknowledged that recruitment for BASIL 1 had been difficult—“it is the reason why my hair is grey; in fact, it is a wonder that I have any hair at all”—but said the vascular community were now more accepting of the need for randomised controlled trials.

Concluding, Bradbury said that there was an “urgent need” to undertake pragmatic, scientifically robust and publically-funded randomised controlled trial of endovascular therapies in severe limb ischaemia that were powered for clinically important endpoints and include a full cost-effectiveness analysis.” He added that the BASIL 2 would look at the health costs and, for “the first time”, the social costs of the interventions in the study. “Without data from such randomised controlled trials, we cannot be sure that endovascular interventions are not going to be associated with net harm or suboptimal use of precious health resources,” Bradbury said.